Configuration Parameters

Configuration Parameters

Descriptions of the Greenplum Database server configuration parameters listed alphabetically.

add_missing_from

Automatically adds missing table references to FROM clauses. Present for compatibility with releases of PostgreSQL prior to 8.1, where this behavior was allowed by default.

Value Range Default Set Classifications
Boolean off master

session

reload

application_name

Sets the application name for a client session. For example, if connecting via psql, this will be set to psql. Setting an application name allows it to be reported in log messages and statistics views.

Value Range Default Set Classifications
string   master

session

reload

array_nulls

This controls whether the array input parser recognizes unquoted NULL as specifying a null array element. By default, this is on, allowing array values containing null values to be entered. Greenplum Database versions before 3.0 did not support null values in arrays, and therefore would treat NULL as specifying a normal array element with the string value 'NULL'.

Value Range Default Set Classifications
Boolean on master

session

reload

authentication_timeout

Maximum time to complete client authentication. This prevents hung clients from occupying a connection indefinitely.

Value Range Default Set Classifications
Any valid time expression (number and unit) 1min local

system

restart

backslash_quote

This controls whether a quote mark can be represented by \' in a string literal. The preferred, SQL-standard way to represent a quote mark is by doubling it ('') but PostgreSQL has historically also accepted \'. However, use of \' creates security risks because in some client character set encodings, there are multibyte characters in which the last byte is numerically equivalent to ASCII \.

Value Range Default Set Classifications
on (allow \' always)

off (reject always)

safe_encoding (allow only if client encoding does not allow ASCII \ within a multibyte character)

safe_encoding master

session

reload

block_size

Reports the size of a disk block.

Value Range Default Set Classifications
number of bytes 32768 read only

bonjour_name

Specifies the Bonjour broadcast name. By default, the computer name is used, specified as an empty string. This option is ignored if the server was not compiled with Bonjour support.

Value Range Default Set Classifications
string unset master

system

restart

check_function_bodies

When set to off, disables validation of the function body string during CREATE FUNCTION. Disabling validation is occasionally useful to avoid problems such as forward references when restoring function definitions from a dump.

Value Range Default Set Classifications
Boolean on master

session

reload

client_encoding

Sets the client-side encoding (character set). The default is to use the same as the database encoding. See Supported Character Sets in the PostgreSQL documentation.

Value Range Default Set Classifications
character set UTF8 master

session

reload

client_min_messages

Controls which message levels are sent to the client. Each level includes all the levels that follow it. The later the level, the fewer messages are sent.

Value Range Default Set Classifications
DEBUG5

DEBUG4

DEBUG3

DEBUG2

DEBUG1

LOG NOTICE

WARNING

ERROR

FATAL

PANIC

NOTICE master

session

reload

cpu_index_tuple_cost

For the legacy query optimizer (planner), sets the estimate of the cost of processing each index row during an index scan. This is measured as a fraction of the cost of a sequential page fetch.

Value Range Default Set Classifications
floating point 0.005 master

session

reload

cpu_operator_cost

For the legacy query optimizer (planner), sets the estimate of the cost of processing each operator in a WHERE clause. This is measured as a fraction of the cost of a sequential page fetch.

Value Range Default Set Classifications
floating point 0.0025 master

session

reload

cpu_tuple_cost

For the legacy query optimizer (planner), Sets the estimate of the cost of processing each row during a query. This is measured as a fraction of the cost of a sequential page fetch.

Value Range Default Set Classifications
floating point 0.01 master

session

reload

cursor_tuple_fraction

Tells the legacy query optimizer (planner) how many rows are expected to be fetched in a cursor query, thereby allowing the legacy optimizer to use this information to optimize the query plan. The default of 1 means all rows will be fetched.

Value Range Default Set Classifications
integer 1 master

session

reload

custom_variable_classes

Specifies one or several class names to be used for custom variables. A custom variable is a variable not normally known to the server but used by some add-on modules. Such variables must have names consisting of a class name, a dot, and a variable name.

Value Range Default Set Classifications
comma-separated list of class names unset local

system

restart

DateStyle

Sets the display format for date and time values, as well as the rules for interpreting ambiguous date input values. This variable contains two independent components: the output format specification and the input/output specification for year/month/day ordering.

Value Range Default Set Classifications
<format>, <date style>

where:

<format> is ISO, Postgres, SQL, or German

<date style> is DMY, MDY, or YMD

ISO, MDY master

session

reload

db_user_namespace

This enables per-database user names. If on, you should create users as username@dbname. To create ordinary global users, simply append @ when specifying the user name in the client.

Value Range Default Set Classifications
Boolean off local

system

restart

deadlock_timeout

The time to wait on a lock before checking to see if there is a deadlock condition. On a heavily loaded server you might want to raise this value. Ideally the setting should exceed your typical transaction time, so as to improve the odds that a lock will be released before the waiter decides to check for deadlock.

Value Range Default Set Classifications
Any valid time expression (number and unit) 1s local

system

restart

debug_assertions

Turns on various assertion checks.

Value Range Default Set Classifications
Boolean off local

system

restart

debug_pretty_print

Indents debug output to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower.

Value Range Default Set Classifications
Boolean off master

session

reload

debug_print_parse

For each executed query, prints the resulting parse tree. client_min_messages or log_min_messages must be DEBUG1 or lower.

Value Range Default Set Classifications
Boolean off master

session

reload

debug_print_plan

For each executed query, prints the Greenplum parallel query execution plan. client_min_messages or log_min_messages must be DEBUG1 or lower.

Value Range Default Set Classifications
Boolean off master

session

reload

debug_print_prelim_plan

For each executed query, prints the preliminary query plan. client_min_messages or log_min_messages must be DEBUG1 or lower.

Value Range Default Set Classifications
Boolean off master

session

reload

debug_print_rewritten

For each executed query, prints the query rewriter output. client_min_messages or log_min_messages must be DEBUG1 or lower.

Value Range Default Set Classifications
Boolean off master

session

reload

debug_print_slice_table

For each executed query, prints the Greenplum query slice plan. client_min_messages or log_min_messages must be DEBUG1 or lower.

Value Range Default Set Classifications
Boolean off master

session

reload

default_statistics_target

Sets the default statistics target for table columns that have not had a column-specific target set via ALTER TABLE SET STATISTICS. Larger values increase the time needed to do ANALYZE, but may improve the quality of the legacy query optimizer (planner) estimates.

Value Range Default Set Classifications
integer > 0 25 master

session

reload

default_tablespace

The default tablespace in which to create objects (tables and indexes) when a CREATE command does not explicitly specify a tablespace.

Value Range Default Set Classifications
name of a tablespace unset master

session

reload

default_transaction_isolation

Controls the default isolation level of each new transaction.

Value Range Default Set Classifications
read committed

read uncommitted

serializable

read committed master

session

reload

default_transaction_read_only

Controls the default read-only status of each new transaction. A read-only SQL transaction cannot alter non-temporary tables.

Value Range Default Set Classifications
Boolean off master

session

reload

dynamic_library_path

If a dynamically loadable module needs to be opened and the file name specified in the CREATE FUNCTION or LOAD command does not have a directory component (i.e. the name does not contain a slash), the system will search this path for the required file. The compiled-in PostgreSQL package library directory is substituted for $libdir. This is where the modules provided by the standard PostgreSQL distribution are installed.

Value Range Default Set Classifications
a list of absolute directory paths separated by colons $libdir local

system

restart

effective_cache_size

Sets the assumption about the effective size of the disk cache that is available to a single query for the legacy query optimizer (planner). This is factored into estimates of the cost of using an index; a higher value makes it more likely index scans will be used, a lower value makes it more likely sequential scans will be used. This parameter has no effect on the size of shared memory allocated by a Greenplum server instance, nor does it reserve kernel disk cache; it is used only for estimation purposes.

Value Range Default Set Classifications
floating point 512MB master

session

reload

enable_bitmapscan

Enables or disables the use of bitmap-scan plan types by the legacy query optimizer (planner). Note that this is different than a Bitmap Index Scan. A Bitmap Scan means that indexes will be dynamically converted to bitmaps in memory when appropriate, giving faster index performance on complex queries against very large tables. It is used when there are multiple predicates on different indexed columns. Each bitmap per column can be compared to create a final list of selected tuples.

Value Range Default Set Classifications
Boolean on master

session

reload

enable_groupagg

Enables or disables the use of group aggregation plan types by the legacy query optimizer (planner).

Value Range Default Set Classifications
Boolean on master

session

reload

enable_hashagg

Enables or disables the use of hash aggregation plan types by the legacy query optimizer (planner).

Value Range Default Set Classifications
Boolean on master

session

reload

enable_hashjoin

Enables or disables the use of hash-join plan types by the legacy query optimizer (planner).

Value Range Default Set Classifications
Boolean on master

session

reload

enable_indexscan

Enables or disables the use of index-scan plan types by the legacy query optimizer (planner).

Value Range Default Set Classifications
Boolean on master

session

reload

enable_mergejoin

Enables or disables the use of merge-join plan types by the legacy query optimizer (planner). Merge join is based on the idea of sorting the left- and right-hand tables into order and then scanning them in parallel. So, both data types must be capable of being fully ordered, and the join operator must be one that can only succeed for pairs of values that fall at the 'same place' in the sort order. In practice this means that the join operator must behave like equality.

Value Range Default Set Classifications
Boolean off master

session

reload

enable_nestloop

Enables or disables the use of nested-loop join plans by the legacy query optimizer (planner). It's not possible to suppress nested-loop joins entirely, but turning this variable off discourages the legacy optimizer from using one if there are other methods available.

Value Range Default Set Classifications
Boolean off master

session

reload

enable_seqscan

Enables or disables the use of sequential scan plan types by the legacy query optimizer (planner). It's not possible to suppress sequential scans entirely, but turning this variable off discourages the legacy optimizer from using one if there are other methods available.

Value Range Default Set Classifications
Boolean on master

session

reload

enable_sort

Enables or disables the use of explicit sort steps by the legacy query optimizer (planner). It's not possible to suppress explicit sorts entirely, but turning this variable off discourages the legacy optimizer from using one if there are other methods available.

Value Range Default Set Classifications
Boolean on master

session

reload

enable_tidscan

Enables or disables the use of tuple identifier (TID) scan plan types by the legacy query optimizer (planner).

Value Range Default Set Classifications
Boolean on master

session

reload

escape_string_warning

When on, a warning is issued if a backslash (\) appears in an ordinary string literal ('...' syntax). Escape string syntax (E'...') should be used for escapes, because in future versions, ordinary strings will have the SQL standard-conforming behavior of treating backslashes literally.

Value Range Default Set Classifications
Boolean on master

session

reload

explain_pretty_print

Determines whether EXPLAIN VERBOSE uses the indented or non-indented format for displaying detailed query-tree dumps.

Value Range Default Set Classifications
Boolean on master

session

reload

extra_float_digits

Adjusts the number of digits displayed for floating-point values, including float4, float8, and geometric data types. The parameter value is added to the standard number of digits. The value can be set as high as 2, to include partially-significant digits; this is especially useful for dumping float data that needs to be restored exactly. Or it can be set negative to suppress unwanted digits.

Value Range Default Set Classifications
integer 0 master

session

reload

filerep_mirrorvalidation_during_resync

The default setting false improves Greenplum Database performance during incremental resynchronization of segment mirrors. Setting the value to true enables checking for the existence of files for all relations on the segment mirror during incremental resynchronization. Checking for files degrades performance of the incremental resynchronization process but provides a minimal check of database objects.

Value Range Default Set Classifications
Boolean false master

session

reload

from_collapse_limit

The legacy query optimizer (planner) will merge sub-queries into upper queries if the resulting FROM list would have no more than this many items. Smaller values reduce planning time but may yield inferior query plans.

Value Range Default Set Classifications
1-n 20 master

session

reload

gp_adjust_selectivity_for_outerjoins

Enables the selectivity of NULL tests over outer joins.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_analyze_relative_error

Sets the estimated acceptable error in the cardinality of the table " a value of 0.5 is supposed to be equivalent to an acceptable error of 50% (this is the default value used in PostgreSQL). If the statistics collected during ANALYZE are not producing good estimates of cardinality for a particular table attribute, decreasing the relative error fraction (accepting less error) tells the system to sample more rows.

Value Range Default Set Classifications
floating point < 1.0 0.25 master

session

reload

gp_appendonly_compaction

Enables compacting segment files during VACUUM commands. When disabled, VACUUM only truncates the segment files to the EOF value, as is the current behavior. The administrator may want to disable compaction in high I/O load situations or low space situations.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_appendonly_compaction_threshold

Specifies the threshold ratio (as a percentage) of hidden rows to total rows that triggers compaction of the segment file when VACUUM is run without the FULL option (a lazy vacuum). If the ratio of hidden rows in a segment file on a segment is less than this threshold, the segment file is not compacted, and a log message is issued.

Value Range Default Set Classifications
integer (%) 10 master

session

reload

gp_autostats_mode

Specifies the mode for triggering automatic statistics collection with ANALYZE. The on_no_stats option triggers statistics collection for CREATE TABLE AS SELECT, INSERT, or COPY operations on any table that has no existing statistics.

The on_change option triggers statistics collection only when the number of rows affected exceeds the threshold defined by gp_autostats_on_change_threshold. Operations that can trigger automatic statistics collection with on_change are:

CREATE TABLE AS SELECT

UPDATE

DELETE

INSERT

COPY

Default is on_no_stats.

Note: For partitioned tables, automatic statistics collection is not triggered if data is inserted from the top-level parent table of a partitioned table.

Automatic statistics collection is triggered if data is inserted directly in a leaf table (where the data is stored) of the partitioned table. Statistics are collected only on the leaf table.

Value Range Default Set Classifications
none

on_change

on_no_stats

on_no_ stats master

session

reload

gp_autostats_mode_in_functions

Specifies the mode for triggering automatic statistics collection with ANALYZE for statements in procedural language functions. The none option disables statistics collection. The on_no_stats option triggers statistics collection for CREATE TABLE AS SELECT, INSERT, or COPY operations that are executed in functions on any table that has no existing statistics.

The on_change option triggers statistics collection only when the number of rows affected exceeds the threshold defined by gp_autostats_on_change_threshold. Operations in functions that can trigger automatic statistics collection with on_change are:

CREATE TABLE AS SELECT

UPDATE

DELETE

INSERT

COPY

Value Range Default Set Classifications
none

on_change

on_no_stats

none master

session

reload

gp_autostats_on_change_threshold

Specifies the threshold for automatic statistics collection when gp_autostats_mode is set to on_change. When a triggering table operation affects a number of rows exceeding this threshold, ANALYZE is added and statistics are collected for the table.

Value Range Default Set Classifications
integer 2147483647 master

session

reload

gp_backup_directIO

Direct I/O allows Greenplum Database to bypass the buffering of memory within the file system cache for backup. When Direct I/O is used for a file, data is transferred directly from the disk to the application buffer, without the use of the file buffer cache.

Direct I/O is supported only on Red Hat Enterprise Linux, CentOS, and SUSE.

Value Range Default Set Classifications
on, off off local

session

reload

gp_backup_directIO_read_chunk_mb

Sets the chunk size in MB when Direct I/O is enabled with gp_backup_directIO. The default chunk size is 20MB.

The default value is the optimal setting. Decreasing it will increase the backup time and increasing it will result in little change to backup time.

Value Range Default Set Classifications
1-200 20 MB local

session

reload

gp_cached_segworkers_threshold

When a user starts a session with Greenplum Database and issues a query, the system creates groups or 'gangs' of worker processes on each segment to do the work. After the work is done, the segment worker processes are destroyed except for a cached number which is set by this parameter. A lower setting conserves system resources on the segment hosts, but a higher setting may improve performance for power-users that want to issue many complex queries in a row.

Value Range Default Set Classifications
integer > 0 5 master

session

reload

gp_command_count

Shows how many commands the master has received from the client. Note that a single SQLcommand might actually involve more than one command internally, so the counter may increment by more than one for a single query. This counter also is shared by all of the segment processes working on the command.

Value Range Default Set Classifications
integer > 0 1 read only

gp_connectemc_mode

Controls the ConnectEMC event logging and dial-home capabilities of Greenplum Command Center on the EMC Greenplum Data Computing Appliance (DCA). ConnectEMC must be installed in order to generate events.

Note: This parameter is deprecated. The parameter will be removed in a future release.

Allowed values are:

on (the default) - log events to the gpperfmon database and send dial-home notifications to Dell EMC Support

off - turns off ConnectEMC event logging and dial-home capabilities

local - log events to the gpperfmon database only

remote - sends dial-home notifications to Pivotal Support (does not log events to the gpperfmon database)

Value Range Default Set Classifications
on, off, local, remote on master

system

restart

superuser

gp_connection_send_timeout

Timeout for sending data to unresponsive Greenplum Database user clients during query processing. A value of 0 disables the timeout, Greenplum Database waits indefinitely for a client. When the timeout is reached, the query is cancelled with this message:
Could not send data to client: Connection timed out.
Value Range Default Set Classifications
number of seconds 3600 (1 hour) master

system

reload

gp_connections_per_thread

A value larger than or equal to the number of primary segments means that each slice in a query plan will get its own thread when dispatching to the segments. A value of 0 indicates that the dispatcher should use a single thread when dispatching all query plan slices to a segment. Lower values will use more threads, which utilizes more resources on the master. Typically, the default does not need to be changed unless there is a known throughput performance problem.

Value Range Default Set Classifications
integer 64 master

session

reload

gp_content

The local content id if a segment.

Value Range Default Set Classifications
integer   read only

gp_create_table_random_default_distribution

Controls table creation when a Greenplum Database table is created with a CREATE TABLE or CREATE TABLE AS command that does not contain a DISTRIBUTED BY clause.

For CREATE TABLE, if the value of the parameter is off (the default), and the table creation command does not contain a DISTRIBUTED BY clause, Greenplum Database chooses the table distribution key based on the command. If the LIKE or INHERITS clause is specified in table creation command, the created table uses the same distribution key as the source or parent table.

If the value of the parameter is set to on, Greenplum Database follows these rules to create a table when the DISTRIBUTED BY clause is not specified:
  • If PRIMARY KEY or UNIQUE columns are not specified, the distribution of the table is random (DISTRIBUTED RANDOMLY). Table distribution is random even if the table creation command contains the LIKE or INHERITS clause.
  • If PRIMARY KEY or UNIQUE columns are specified, a DISTRIBUTED BY clause must also be specified. If a DISTRIBUTED BY clause is not specified as part of the table creation command, the command fails.
For a CREATE TABLE AS command that does not contain a distribution clause:
  • If the legacy query optimizer creates the table, and the value of the parameter is off, the table distribution policy is determined based on the command.
  • If the legacy query optimizer creates the table, and the value of the parameter is on, the table distribution policy is random.
  • If GPORCA creates the table, the table distribution policy is random. The parameter value has no affect.

For information about the legacy query optimizer and GPORCA, see "Querying Data" in the Greenplum Database Administrator Guide.

Value Range Default Set Classifications
boolean off master

system

reload

gp_dbid

The local content dbid if a segment.

Value Range Default Set Classifications
integer   read only

gp_debug_linger

Number of seconds for a Greenplum process to linger after a fatal internal error.

Value Range Default Set Classifications
Any valid time expression (number and unit) 0 master

session

reload

gp_default_storage_options

Set the default values for the following table storage options when a table is created with the CREATE TABLE command.
  • APPENDONLY
  • BLOCKSIZE
  • CHECKSUM
  • COMPRESSTYPE
  • COMPRESSLEVEL
  • ORIENTATION

Specify multiple storage option values as a comma separated list.

You can set the storage options with this parameter instead of specifying the table storage options in the WITH of the CREATE TABLE command. The table storage options that are specified with the CREATE TABLE command override the values specified by this parameter.

Not all combinations of storage option values are valid. If the specified storage options are not valid, an error is returned. See the CREATE TABLE command for information about table storage options.

The defaults can be set for a database and user. If the server configuration parameter is set at different levels, this the order of precedence, from highest to lowest, of the table storage values when a user logs into a database and creates a table:

  1. The values specified in a CREATE TABLE command with the WITH clause or ENCODING clause
  2. The value of gp_default_storage_options that set for the user with the ALTER ROLE...SET command
  3. The value of gp_default_storage_options that is set for the database with the ALTER DATABASE...SET command
  4. The value of gp_default_storage_options that is set for the Greenplum Database system with the gpconfig utility

The parameter value is not cumulative. For example, if the parameter specifies the APPENDONLY and COMPRESSTYPE options for a database and a user logs in and sets the parameter to specify the value for the ORIENTATION option, the APPENDONLY, and COMPRESSTYPE values set at the database level are ignored.

This example ALTER DATABASE command sets the default ORIENTATION and COMPRESSTYPE table storage options for the database mystest.
ALTER DATABASE mytest SET gp_default_storage_options = 'orientation=column, compresstype=rle_type'

To create an append-optimized table in the mytest database with column-oriented table and RLE compression. The user needs to specify only APPENDONLY=TRUE in the WITH clause.

This example gpconfig utility command sets the default storage option for a Greenplum Database system. If you set the defaults for multiple table storage options, the value must be enclosed in single quotes and then in double quotes.
gpconfig -c 'gp_default_storage_options' -v "'appendonly=true, orientation=column'"
This example gpconfig utility command shows the value of the parameter. The parameter value must be consistent across the Greenplum Database master and all segments.
gpconfig -s 'gp_default_storage_options'
Value Range Default Set Classifications 1
APPENDONLY= TRUE | FALSE

BLOCKSIZE= integer between 8192 and 2097152

CHECKSUM= TRUE | FALSE

COMPRESSTYPE= ZLIB | QUICKLZ | RLE_TYPE | NONE

COMPRESSLEVEL= integer between 0 and 9

ORIENTATION= ROW | COLUMN

APPENDONLY=FALSE

BLOCKSIZE=32768

CHECKSUM=TRUE

COMPRESSTYPE=none

COMPRESSLEVEL=0

ORIENTATION=ROW

master

session

reload

Note: 1The set classification when the parameter is set at the system level with the gpconfig utility.

gp_dynamic_partition_pruning

Enables plans that can dynamically eliminate the scanning of partitions.

Value Range Default Set Classifications
on/off on master

session

reload

gp_email_from

The email address used to send email alerts, in the format of:

'username@example.com'

or

'Name <username@example.com>'

Value Range Default Set Classifications
string   master

system

reload

superuser

gp_email_smtp_password

The password/passphrase used to authenticate with the SMTP server.

Value Range Default Set Classifications
string   master

system

reload

superuser

gp_email_smtp_server

The fully qualified domain name or IP address and port of the SMTP server to use to send the email alerts. Must be in the format of:

smtp_servername.domain.com:port

Value Range Default Set Classifications
string   master

system

reload

superuser

gp_email_smtp_userid

The user id used to authenticate with the SMTP server.

Value Range Default Set Classifications
string   master

system

reload

superuser

gp_email_to

A semi-colon (;) separated list of email addresses to receive email alert messages to in the format of: 'username@example.com'

or

'Name <username@example.com>'

If this parameter is not set, then email alerts are disabled.

Value Range Default Set Classifications
string   master

system

reload

superuser

gp_enable_adaptive_nestloop

Enables the use a new type of join node called "Adaptive Nestloop" at query execution time by the legacy query optimizer (planner). This causes the legacy optimizer to favor a hash-join over a nested-loop join if the number of rows on the outer side of the join exceeds a precalculated threshold. This parameter improves performance of index operations, which previously favored slower nested-loop joins.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_agg_distinct

Enables or disables two-phase aggregation to compute a single distinct-qualified aggregate. This applies only to subqueries that include a single distinct-qualified aggregate function.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_agg_distinct_pruning

Enables or disables three-phase aggregation and join to compute distinct-qualified aggregates. This applies only to subqueries that include one or more distinct-qualified aggregate functions.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_direct_dispatch

Enables or disables the dispatching of targeted query plans for queries that access data on a single segment. When on, queries that target rows on a single segment will only have their query plan dispatched to that segment (rather than to all segments). This significantly reduces the response time of qualifying queries as there is no interconnect setup involved. Direct dispatch does require more CPU utilization on the master.

Value Range Default Set Classifications
Boolean on master

system

restart

gp_enable_exchange_default_partition

Controls availability of the EXCHANGE DEFAULT PARTITION clause for ALTER TABLE. The default value for the parameter is off. The clause is not available and Greenplum Database returns an error if the clause is specified in an ALTER TABLE command.

If the value is on, Greenplum Database returns a warning stating that exchanging the default partition might result in incorrect results due to invalid data in the default partition.

Warning: Before you exchange the default partition, you must ensure the data in the table to be exchanged, the new default partition, is valid for the default partition. For example, the data in the new default partition must not contain data that would be valid in other leaf child partitions of the partitioned table. Otherwise, queries against the partitioned table with the exchanged default partition that are executed by GPORCA might return incorrect results.
Value Range Default Set Classifications
Boolean off master

session

reload

gp_enable_fallback_plan

Allows use of disabled plan types when a query would not be feasible without them.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_fast_sri

When set to on, the legacy query optimizer (planner) plans single row inserts so that they are sent directly to the correct segment instance (no motion operation required). This significantly improves performance of single-row-insert statements.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_gpperfmon

Enables or disables the data collection agents of Greenplum Command Center.

Value Range Default Set Classifications
Boolean off local

system

restart

gp_enable_groupext_distinct_gather

Enables or disables gathering data to a single node to compute distinct-qualified aggregates on grouping extension queries. When this parameter and gp_enable_groupext_distinct_pruning are both enabled, the legacy query optimizer (planner) uses the cheaper plan.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_groupext_distinct_pruning

Enables or disables three-phase aggregation and join to compute distinct-qualified aggregates on grouping extension queries. Usually, enabling this parameter generates a cheaper query plan that the legacy query optimizer (planner) will use in preference to existing plan.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_multiphase_agg

Enables or disables the use of two or three-stage parallel aggregation plans legacy query optimizer (planner). This approach applies to any subquery with aggregation. If gp_enable_multiphase_agg is off, then gp_enable_agg_distinct and gp_enable_agg_distinct_pruning are disabled.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_predicate_propagation

When enabled, the legacy query optimizer (planner) applies query predicates to both table expressions in cases where the tables are joined on their distribution key column(s). Filtering both tables prior to doing the join (when possible) is more efficient.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_preunique

Enables two-phase duplicate removal for SELECT DISTINCT queries (not SELECT COUNT(DISTINCT)). When enabled, it adds an extra SORT DISTINCT set of plan nodes before motioning. In cases where the distinct operation greatly reduces the number of rows, this extra SORT DISTINCT is much cheaper than the cost of sending the rows across the Interconnect.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_sequential_window_plans

If on, enables non-parallel (sequential) query plans for queries containing window function calls. If off, evaluates compatible window functions in parallel and rejoins the results. This is an experimental parameter.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_relsize_collection

Enables the legacy query optimizer (planner) to use the estimated size of a table (pg_relation_size function) if there are no statistics for the table. By default, the planner uses a default value to estimate the number of rows if statistics are not available. The default behavior improves query optimization time and reduces resource queue usage in heavy workloads, but can lead to suboptimal plans.

Value Range Default Set Classifications
Boolean off master

session

reload

gp_enable_sort_distinct

Enable duplicates to be removed while sorting.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_enable_sort_limit

Enable LIMIT operation to be performed while sorting. Sorts more efficiently when the plan requires the first limit_number of rows at most.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_external_enable_exec

Enables or disables the use of external tables that execute OS commands or scripts on the segment hosts (CREATE EXTERNAL TABLE EXECUTE syntax). Must be enabled if using the Command Center or MapReduce features.

Value Range Default Set Classifications
Boolean on master

system

restart

gp_external_grant_privileges

In releases prior to 4.0, enables or disables non-superusers to issue a CREATE EXTERNAL [WEB] TABLE command in cases where the LOCATION clause specifies http or gpfdist. In releases after 4.0, the ability to create an external table can be granted to a role using CREATE ROLE or ALTER ROLE.

Note: This server configuration parameter is deprecated and will be removed in a future release.
Value Range Default Set Classifications
Boolean off master

system

restart

gp_external_max_segs

Sets the number of segments that will scan external table data during an external table operation, the purpose being not to overload the system with scanning data and take away resources from other concurrent operations. This only applies to external tables that use the gpfdist:// protocol to access external table data.

Value Range Default Set Classifications
integer 64 master

session

reload

gp_filerep_tcp_keepalives_count

How many keepalives may be lost before the connection is considered dead. A value of 0 uses the system default. If TCP_KEEPCNT is not supported, this parameter must be 0.

Use this parameter for all connections that are between a primary and mirror segment. Use tcp_keepalives_count for settings that are not between a primary and mirror segment.

Value Range Default Set Classifications
number of lost keepalives 2 local

system

restart

gp_filerep_tcp_keepalives_idle

Number of seconds between sending keepalives on an otherwise idle connection. A value of 0 uses the system default. If TCP_KEEPIDLE is not supported, this parameter must be 0.

Use this parameter for all connections that are between a primary and mirror segment. Use tcp_keepalives_idle for settings that are not between a primary and mirror segment.

Value Range Default Set Classifications
number of seconds 1 min local

system

restart

gp_filerep_tcp_keepalives_interval

How many seconds to wait for a response to a keepalive before retransmitting. A value of 0 uses the system default. If TCP_KEEPINTVL is not supported, this parameter must be 0.

Use this parameter for all connections that are between a primary and mirror segment. Use tcp_keepalives_interval for settings that are not between a primary and mirror segment.

Value Range Default Set Classifications
number of seconds 30 sec local

system

restart

gp_fts_probe_interval

Specifies the polling interval for the fault detection process (ftsprobe). The ftsprobe process will take approximately this amount of time to detect a segment failure.

Value Range Default Set Classifications
10 - 3600 seconds 1min master

system

restart

gp_fts_probe_retries

Specifies the number of times the fault detection process (ftsprobe) attempts to connect to a segment before reporting segment failure.

Value Range Default Set Classifications
integer 5 master

system

restart

gp_fts_probe_threadcount

Specifies the number of ftsprobe threads to create. This parameter should be set to a value equal to or greater than the number of segments per host.

Value Range Default Set Classifications
1 - 128 16 master

system

restart

gp_fts_probe_timeout

Specifies the allowed timeout for the fault detection process (ftsprobe) to establish a connection to a segment before declaring it down.

Value Range Default Set Classifications
10 - 3600 seconds 20 secs master

system

restart

gp_log_fts

Controls the amount of detail the fault detection process (ftsprobe) writes to the log file.

Value Range Default Set Classifications
OFF

TERSE

VERBOSE

DEBUG

TERSE master

system

restart

gp_log_gang

Controls the amount of information that is written to the log file about query worker process creation and query management. The default value is OFF, do not log information.

Value Range Default Set Classifications
OFF

TERSE

VERBOSE

DEBUG

OFF master

session

restart

gp_gpperfmon_send_interval

Sets the frequency that the Greenplum Database server processes send query execution updates to the data collection agent processes used by Command Center. Query operations (iterators) executed during this interval are sent through UDP to the segment monitor agents. If you find that an excessive number of UDP packets are dropped during long-running, complex queries, you may consider increasing this value.

Value Range Default Set Classifications
Any valid time expression (number and unit) 1sec master

system

restart

gpperfmon_log_alert_level

Controls which message levels are written to the gpperfmon log. Each level includes all the levels that follow it. The later the level, the fewer messages are sent to the log.

Note: If the Greenplum Database Command Center is installed and is monitoring the database, the default value is warning.
Value Range Default Set Classifications
none

warning

error

fatal

panic

none local

system

restart

gp_hadoop_home

When using Pivotal HD, specify the installation directory for Hadoop. For example, the default installation directory is /usr/lib/gphd.

When using Greenplum HD 1.2 or earlier, specify the same value as the HADOOP_HOME environment variable.

Value Range Default Set Classifications
Valid directory name Value of HADOOP_HOME local

session

reload

gp_hadoop_target_version

The installed version of Greenplum Hadoop target.

Value Range Default Set Classifications
gphd-1.0 1

gphd-1.1 1

gphd-1.2 1

gphd-2.0 1

gphd-3.0 1

gpmr-1.0 1

gpmr-1.2

hadoop2

hdp2

cdh5

cdh4.1 1

gphd-1.1 local

session

reload

Note: 1Support for these Hadoop distributions have been deprecated and will be removed in a future release: Pivotal HD, Greenplum HD, Cloudera CDH 4.1 - CDH 4.7, and MapR 1.x, 2.x, 3.x.

For the latest information regarding supported Hadoop distributions, see the Greenplum Database Release Notes for your release.

gp_hashjoin_tuples_per_bucket

Sets the target density of the hash table used by HashJoin operations. A smaller value will tend to produce larger hash tables, which can increase join performance.

Value Range Default Set Classifications
integer 5 master

session

reload

gp_idf_deduplicate

Changes the strategy to compute and process MEDIAN, and PERCENTILE_DISC.

Value Range Default Set Classifications
auto

none

force

auto master

session

reload

gp_initial_bad_row_limit

For the parameter value n, Greenplum Database stops processing input rows when you import data with the COPY command or from an external table if the first n rows processed contain formatting errors. If a valid row is processed within the first n rows, Greenplum Database continues processing input rows.

Setting the value to 0 disables this limit.

The SEGMENT REJECT LIMIT clause can also be specified for the COPY command or the external table definition to limit the number of rejected rows.

INT_MAX is the largest value that can be stored as an integer on your system.

Value Range Default Set Classifications
integer 0 - INT_MAX 1000 master

session

reload

gp_inline_simple_cte

Controls how the legacy query optimizer handles a simple common table expression (CTE) query (a query that contains a WITH clause). A simple CTE does not contain another CTE, is not correlated, and is not referenced more than once.

For a simple CTE, if the value is true (the default), the legacy query optimizer inlines the CTE, replacing the CTE with a subplan. If the value is false, the legacy query optimizer does not inline the CTE.

This parameter can be set for a database system, an individual database, or a session or query.

Value Range Default Set Classifications
Boolean true master

session

reload

gp_interconnect_fc_method

Specifies the flow control method used for UDP interconnect when the value of gp_interconnect_type is UDPIFC.

For capacity based flow control, senders do not send packets when receivers do not have the capacity.

Loss based flow control is based on capacity based flow control, and also tunes the sending speed according to packet losses.

Value Range Default Set Classifications
CAPACITY

LOSS

LOSS master

session

reload

gp_interconnect_hash_multiplier

Sets the size of the hash table used by the Greenplum Database to track interconnect connections when gp_interconnect_type is UDPIFC. This number is multiplied by the number of segments to determine the number of buckets in the hash table. Increasing the value may increase interconnect performance for complex multi-slice queries (while consuming slightly more memory on the segment hosts).

Value Range Default Set Classifications
2-25 2 master

session

reload

gp_interconnect_queue_depth

When gp_interconnect_type is UDPIFC, sets the amount of data per-peer to be queued by the Greenplum Database interconnect on receivers (when data is received but no space is available to receive it the data will be dropped, and the transmitter will need to resend it). Increasing the depth from its default value will cause the system to use more memory; but may increase performance. It is reasonable for this to be set between 1 and 10. Queries with data skew potentially perform better when this is increased. Increasing this may radically increase the amount of memory used by the system.

Value Range Default Set Classifications
1-2048 4 master

session

reload

gp_interconnect_setup_timeout

Specifies the amount of time to wait for the Greenplum Database interconnect to complete setup before it times out.

Value Range Default Set Classifications
Any valid time expression (number and unit) 2 hours master

session

reload

gp_interconnect_snd_queue_depth

Sets the amount of data per-peer to be queued by the UDP interconnect on senders when gp_interconnect_type is set to UDPIFC. Increasing the depth from its default value will cause the system to use more memory; but may increase performance. Reasonable values for this parameter are between 1 and 4. Increasing the value might radically increase the amount of memory used by the system. For information about interconnect types, see gp_interconnect_type.

Value Range Default Set Classifications
1 - 4096 2 master

session

reload

gp_interconnect_type

Sets the networking protocol used for Greenplum Database interconnect traffic. The default interconnect type UDPIFC specifies using UDP protocol with flow control for interconnect traffic. Specify the interconnect flow control method with gp_interconnect_fc_method.

With the TCP protocol, Greenplum Database has an upper limit of 1000 segment instances - less than that if the query workload involves complex, multi-slice queries.

For UDPIFC, Greenplum Database does the additional packet verification and checking not performed by UDP, so reliability and performance is equivalent to TCP.

Value Range Default Set Classifications
TCP

UDPIFC

UDPIFC local

system

restart

gp_log_format

Specifies the format of the server log files. If using gp_toolkit administrative schema, the log files must be in CSV format.

Value Range Default Set Classifications
csv

text

csv local

system

restart

gp_max_csv_line_length

The maximum length of a line in a CSV formatted file that will be imported into the system. The default is 1MB (1048576 bytes). Maximum allowed is 4MB (4194184 bytes). The default may need to be increased if using the gp_toolkit administrative schema to read Greenplum Database log files.

Value Range Default Set Classifications
number of bytes 1048576 local

system

restart

gp_max_databases

The maximum number of databases allowed in a Greenplum Database system.

Value Range Default Set Classifications
integer 16 master

system

restart

gp_max_filespaces

The maximum number of filespaces allowed in a Greenplum Database system.

Value Range Default Set Classifications
integer 8 master

system

restart

gp_max_local_distributed_cache

Sets the maximum number of distributed transaction log entries to cache in the backend process memory of a segment instance.

The log entries contain information about the state of rows that are being accessed by an SQL statement. The information is used to determine which rows are visible to an SQL transaction when executing multiple simultaneous SQL statements in an MVCC environment. Caching distributed transaction log entries locally improves transaction processing speed by improving performance of the row visibility determination process.

The default value is optimal for a wide variety of SQL processing environments.

Value Range Default Set Classifications
integer 1024 local

system

restart

gp_max_packet_size

Sets the tuple-serialization chunk size for the Greenplum Database interconnect.

Value Range Default Set Classifications
512-65536 8192 master

system

restart

gp_max_plan_size

Specifies the total maximum uncompressed size of a query execution plan multiplied by the number of Motion operators (slices) in the plan. If the size of the query plan exceeds the value, the query is cancelled and an error is returned. A value of 0 means that the size of the plan is not monitored.

You can specify a value in kB, MB, or GB. The default unit is kB. For example, a value of 200 is 200kB. A value of 1GB is the same as 1024MB or 1048576kB.

Value Range Default Set Classifications
integer 0 master

superuser

session

gp_max_tablespaces

The maximum number of tablespaces allowed in a Greenplum Database system.

Value Range Default Set Classifications
integer 16 master

system

restart

gp_motion_cost_per_row

Sets the legacy query optimizer (planner) cost estimate for a Motion operator to transfer a row from one segment to another, measured as a fraction of the cost of a sequential page fetch. If 0, then the value used is two times the value of cpu_tuple_cost.

Value Range Default Set Classifications
floating point 0 master

session

reload

gp_num_contents_in_cluster

The number of primary segments in the Greenplum Database system.

Value Range Default Set Classifications
- - read only

gp_reject_percent_threshold

For single row error handling on COPY and external table SELECTs, sets the number of rows processed before SEGMENT REJECT LIMIT n PERCENT starts calculating.

Value Range Default Set Classifications
1-n 300 master

session

reload

gp_reraise_signal

If enabled, will attempt to dump core if a fatal server error occurs.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_resqueue_memory_policy

Enables Greenplum memory management features. The distribution algorithm eager_free takes advantage of the fact that not all operators execute at the same time (in Greenplum Database 4.2 and later). The query plan is divided into stages and Greenplum Database eagerly frees memory allocated to a previous stage at the end of that stage's execution, then allocates the eagerly freed memory to the new stage.

When set to none, memory management is the same as in Greenplum Database releases prior to 4.1.

When set to auto, query memory usage is controlled by statement_mem and resource queue memory limits.

Value Range Default Set Classifications
none, auto, eager_free eager_free local

system

restart/reload

gp_resqueue_priority

Enables or disables query prioritization. When this parameter is disabled, existing priority settings are not evaluated at query run time.

Value Range Default Set Classifications
Boolean on local

system

restart

gp_resqueue_priority_cpucores_per_segment

Specifies the number of CPU units allocated per segment instance. For example, if a Greenplum Database cluster has 10-core segment hosts that are configured with four segments, set the value for the segment instances to 2.5. For the master instance, the value would be 10. A master host typically has only the master instance running on it, so the value for the master should reflect the usage of all available CPU cores.

Incorrect settings can result in CPU under-utilization or query prioritization not working as designed.

The default values for the Greenplum Data Computing Appliance V2 are 4 for segments and 25 for the master.

Value Range Default Set Classifications
0.1 - 512.0 4 local

system

restart

gp_resqueue_priority_sweeper_interval

Specifies the interval at which the sweeper process evaluates current CPU usage. When a new statement becomes active, its priority is evaluated and its CPU share determined when the next interval is reached.

Value Range Default Set Classifications
500 - 15000 ms 1000 local

system

restart

gp_role

The role of this server process " set to dispatch for the master and execute for a segment.

Value Range Default Set Classifications
dispatch

execute

utility

  read only

gp_safefswritesize

Specifies a minimum size for safe write operations to append-optimized tables in a non-mature file system. When a number of bytes greater than zero is specified, the append-optimized writer adds padding data up to that number in order to prevent data corruption due to file system errors. Each non-mature file system has a known safe write size that must be specified here when using Greenplum Database with that type of file system. This is commonly set to a multiple of the extent size of the file system; for example, Linux ext3 is 4096 bytes, so a value of 32768 is commonly used.

Value Range Default Set Classifications
integer 0 local

system

restart

gp_segment_connect_timeout

Time that the Greenplum interconnect will try to connect to a segment instance over the network before timing out. Controls the network connection timeout between master and primary segments, and primary to mirror segment replication processes.

Value Range Default Set Classifications
Any valid time expression (number and unit) 10min local

system

reload

gp_segments_for_planner

Sets the number of primary segment instances for the legacy query optimizer (planner) to assume in its cost and size estimates. If 0, then the value used is the actual number of primary segments. This variable affects the legacy optimizer's estimates of the number of rows handled by each sending and receiving process in Motion operators.

Value Range Default Set Classifications
0-n 0 master

session

reload

gp_session_id

A system assigned ID number for a client session. Starts counting from 1 when the master instance is first started.

Value Range Default Set Classifications
1-n 14 read only

gp_set_proc_affinity

If enabled, when a Greenplum server process (postmaster) is started it will bind to a CPU.

Value Range Default Set Classifications
Boolean off master

system

restart

gp_set_read_only

Set to on to disable writes to the database. Any in progress transactions must finish before read-only mode takes affect.

Value Range Default Set Classifications
Boolean off master

system

restart

gp_snmp_community

Set to the community name you specified for your environment.

Value Range Default Set Classifications
SNMP community name public master

system

reload

gp_snmp_monitor_address

The hostname:port of your network monitor application. Typically, the port number is 162. If there are multiple monitor addresses, separate them with a comma.

Value Range Default Set Classifications
hostname:port   master

system

reload

gp_snmp_use_inform_or_trap

Trap notifications are SNMP messages sent from one application to another (for example, between Greenplum Database and a network monitoring application). These messages are unacknowledged by the monitoring application, but generate less network overhead.

Inform notifications are the same as trap messages, except that the application sends an acknowledgement to the application that generated the alert.

Value Range Default Set Classifications
inform

trap

trap master

system

reload

gp_statistics_pullup_from_child_partition

Enables the use of statistics from child tables when planning queries on the parent table by the legacy query optimizer (planner).

Value Range Default Set Classifications
Boolean on master

session

reload

gp_statistics_use_fkeys

When enabled, allows the legacy query optimizer (planner) to use foreign key information stored in the system catalog to optimize joins between foreign keys and primary keys.

Value Range Default Set Classifications
Boolean off master

session

reload

gp_strict_xml_parse

Controls the XML validation performed by Greenplum Database.

When the value is true, the default and the data is not a valid XML document, Greenplum Database returns an error. When the value is false and the data is neither a valid XML document or a valid XML fragment, Greenplum Database returns an error.

The parameter can be set for a database system, an individual database, or a session.

Note: The Greenplum Database utility gpdbrestore sets this parameter to false during a restore operation. This allows the operation to restore any valid XML data from a backup if needed.
Value Range Default Set Classifications
Boolean true master

session

reload

gp_vmem_idle_resource_timeout

If a database session is idle for longer than the time specified, the session will free system resources (such as shared memory), but remain connected to the database. This allows more concurrent connections to the database at one time.

Value Range Default Set Classifications
Any valid time expression (number and unit) 18s master

system

reload

gp_vmem_protect_limit

Sets the amount of memory (in number of MBs) that all postgres processes of an active segment instance can consume. If a query causes this limit to be exceeded, memory will not be allocated and the query will fail. Note that this is a local parameter and must be set for every segment in the system (primary and mirrors). When setting the parameter value, specify only the numeric value. For example, to specify 4096MB, use the value 4096. Do not add the units MB to the value.

To prevent over-allocation of memory, these calculations can estimate a safe gp_vmem_protect_limit value.

First calculate the value gp_vmem. This is the Greenplum Database memory available on a host
gp_vmem = ((SWAP + RAM) – (7.5GB + 0.05 * RAM)) / 1.7

where SWAP is the host swap space and RAM is the RAM on the host in GB.

Next, calculate the max_acting_primary_segments. This is the maximum number of primary segments that can be running on a host when mirror segments are activated due to a failure. With mirrors arranged in a 4-host block with 8 primary segments per host, for example, a single segment host failure would activate two or three mirror segments on each remaining host in the failed host's block. The max_acting_primary_segments value for this configuration is 11 (8 primary segments plus 3 mirrors activated on failure).

This is the calculation for gp_vmem_protect_limit. The value should be converted to MB.

gp_vmem_protect_limit = gp_vmem / acting_primary_segments

For scenarios where a large number of workfiles are generated, this is the calculation for gp_vmem that accounts for the workfiles.

gp_vmem = ((SWAP + RAM) – (7.5GB + 0.05 * RAM - (300KB * total_#_workfiles))) / 1.7

For information about monitoring and managing workfile usage, see the Greenplum Database Administrator Guide.

Based on the gp_vmem value you can calculate the value for the vm.overcommit_ratio operating system kernel parameter. This parameter is set when you configure each Greenplum Database host.
vm.overcommit_ratio = (RAM - (0.026 * gp_vmem)) / RAM
Note: The default value for the kernel parameter vm.overcommit_ratio in Red Hat Enterprise Linux is 50.

For information about the kernel parameter, see the Greenplum Database Installation Guide.

Value Range Default Set Classifications
integer 8192 local

system

restart

gp_vmem_protect_segworker_cache_limit

If a query executor process consumes more than this configured amount, then the process will not be cached for use in subsequent queries after the process completes. Systems with lots of connections or idle processes may want to reduce this number to free more memory on the segments. Note that this is a local parameter and must be set for every segment.

Value Range Default Set Classifications
number of megabytes 500 local

system

restart

gp_workfile_checksumming

Adds a checksum value to each block of a work file (or spill file) used by HashAgg and HashJoin query operators. This adds an additional safeguard from faulty OS disk drivers writing corrupted blocks to disk. When a checksum operation fails, the query will cancel and rollback rather than potentially writing bad data to disk.

Value Range Default Set Classifications
Boolean on master

session

reload

gp_workfile_compress_algorithm

When a hash aggregation or hash join operation spills to disk during query processing, specifies the compression algorithm to use on the spill files. If using zlib, it must be in your $PATH on all segments.

If your Greenplum database installation uses serial ATA (SATA) disk drives, setting the value of this parameter to zlib might help to avoid overloading the disk subsystem with IO operations.

Value Range Default Set Classifications
none

zlib

none master

session

reload

gp_workfile_limit_files_per_query

Sets the maximum number of temporary spill files (also known as workfiles) allowed per query per segment. Spill files are created when executing a query that requires more memory than it is allocated. The current query is terminated when the limit is exceeded.

Set the value to 0 (zero) to allow an unlimited number of spill files. master session reload

Value Range Default Set Classifications
integer 100000 master

session

reload

gp_workfile_limit_per_query

Sets the maximum disk size an individual query is allowed to use for creating temporary spill files at each segment. The default value is 0, which means a limit is not enforced.

Value Range Default Set Classifications
kilobytes 0 master

session

reload

gp_workfile_limit_per_segment

Sets the maximum total disk size that all running queries are allowed to use for creating temporary spill files at each segment. The default value is 0, which means a limit is not enforced.

Value Range Default Set Classifications
kilobytes 0 local

system

restart

gpperfmon_port

Sets the port on which all data collection agents (for Command Center) communicate with the master.

Value Range Default Set Classifications
integer 8888 master

system

restart

integer_datetimes

Reports whether PostgreSQL was built with support for 64-bit-integer dates and times.

Value Range Default Set Classifications
Boolean on read only

IntervalStyle

Sets the display format for interval values. The value sql_standard produces output matching SQL standard interval literals. The value postgres produces output matching PostgreSQL releases prior to 8.4 when the DateStyle parameter was set to ISO.

The value postgres_verbose produces output matching Greenplum releases prior to 3.3 when the DateStyle parameter was set to non-ISO output.

The value iso_8601 will produce output matching the time interval format with designators defined in section 4.4.3.2 of ISO 8601. See the PostgreSQL 8.4 documentation for more information.

Value Range Default Set Classifications
postgres

postgres_verbose

sql_standard

iso_8601

postgres master

session

reload

join_collapse_limit

The legacy query optimizer (planner) will rewrite explicit inner JOIN constructs into lists of FROM items whenever a list of no more than this many items in total would result. By default, this variable is set the same as from_collapse_limit, which is appropriate for most uses. Setting it to 1 prevents any reordering of inner JOINs. Setting this variable to a value between 1 and from_collapse_limit might be useful to trade off planning time against the quality of the chosen plan (higher values produce better plans).

Value Range Default Set Classifications
1-n 20 master

session

reload

keep_wal_segments

For Greenplum Database master mirroring, sets the maximum number of processed WAL segment files that are saved by the by the active Greenplum Database master if a checkpoint operation occurs.

The segment files are used to sycnronize the active master on the standby master.

Value Range Default Set Classifications
integer 5 master

system

reload

superuser

krb_caseins_users

Sets whether Kerberos user names should be treated case-insensitively. The default is case sensitive (off).

Value Range Default Set Classifications
Boolean off master

system

restart

krb_server_keyfile

Sets the location of the Kerberos server key file.

Value Range Default Set Classifications
path and file name unset master

system

restart

krb_srvname

Sets the Kerberos service name.

Value Range Default Set Classifications
service name postgres master

system

restart

lc_collate

Reports the locale in which sorting of textual data is done. The value is determined when the Greenplum Database array is initialized.

Value Range Default Set Classifications
<system dependent>   read only

lc_ctype

Reports the locale that determines character classifications. The value is determined when the Greenplum Database array is initialized.

Value Range Default Set Classifications
<system dependent>   read only

lc_messages

Sets the language in which messages are displayed. The locales available depends on what was installed with your operating system - use locale -a to list available locales. The default value is inherited from the execution environment of the server. On some systems, this locale category does not exist. Setting this variable will still work, but there will be no effect. Also, there is a chance that no translated messages for the desired language exist. In that case you will continue to see the English messages.

Value Range Default Set Classifications
<system dependent>   local

system

restart

lc_monetary

Sets the locale to use for formatting monetary amounts, for example with the to_char family of functions. The locales available depends on what was installed with your operating system - use locale -a to list available locales. The default value is inherited from the execution environment of the server.

Value Range Default Set Classifications
<system dependent>   local

system

restart

lc_numeric

Sets the locale to use for formatting numbers, for example with the to_char family of functions. The locales available depends on what was installed with your operating system - use locale -a to list available locales. The default value is inherited from the execution environment of the server.

Value Range Default Set Classifications
<system dependent>   local

system

restart

lc_time

This parameter currently does nothing, but may in the future.

Value Range Default Set Classifications
<system dependent>   local

system

restart

listen_addresses

Specifies the TCP/IP address(es) on which the server is to listen for connections from client applications - a comma-separated list of host names and/or numeric IP addresses. The special entry * corresponds to all available IP interfaces. If the list is empty, only UNIX-domain sockets can connect.

Value Range Default Set Classifications
localhost,

host names,

IP addresses,

* (all available IP interfaces)

* master

system

restart

local_preload_libraries

Comma separated list of shared library files to preload at the start of a client session.

Value Range Default Set Classifications
    local

system

restart

log_autostats

Logs information about automatic ANALYZE operations related to gp_autostats_mode and gp_autostats_on_change_threshold.

Value Range Default Set Classifications
Boolean off master

session

reload

superuser

log_connections

This outputs a line to the server log detailing each successful connection. Some client programs, like psql, attempt to connect twice while determining if a password is required, so duplicate "connection received" messages do not always indicate a problem.

Value Range Default Set Classifications
Boolean off local

system

restart

log_disconnections

This outputs a line in the server log at termination of a client session, and includes the duration of the session.

Value Range Default Set Classifications
Boolean off local

system

restart

log_dispatch_stats

When set to "on," this parameter adds a log message with verbose information about the dispatch of the statement.

Value Range Default Set Classifications
Boolean off local

system

restart

log_duration

Causes the duration of every completed statement which satisfies log_statement to be logged.

Value Range Default Set Classifications
Boolean off master

session

reload

superuser

log_error_verbosity

Controls the amount of detail written in the server log for each message that is logged.

Value Range Default Set Classifications
TERSE

DEFAULT

VERBOSE

DEFAULT master

session

reload

superuser

log_executor_stats

For each query, write performance statistics of the query executor to the server log. This is a crude profiling instrument. Cannot be enabled together with log_statement_stats.

Value Range Default Set Classifications
Boolean off local

system

restart

log_hostname

By default, connection log messages only show the IP address of the connecting host. Turning on this option causes logging of the IP address and host name of the Greenplum Database master. Note that depending on your host name resolution setup this might impose a non-negligible performance penalty.

Value Range Default Set Classifications
Boolean off master

system

restart

log_min_duration_statement

Logs the statement and its duration on a single log line if its duration is greater than or equal to the specified number of milliseconds. Setting this to 0 will print all statements and their durations. -1 disables the feature. For example, if you set it to 250 then all SQL statements that run 250ms or longer will be logged. Enabling this option can be useful in tracking down unoptimized queries in your applications.

Value Range Default Set Classifications
number of milliseconds, 0, -1 -1 master

session

reload

superuser

log_min_error_statement

Controls whether or not the SQL statement that causes an error condition will also be recorded in the server log. All SQL statements that cause an error of the specified level or higher are logged. The default is PANIC (effectively turning this feature off for normal use). Enabling this option can be helpful in tracking down the source of any errors that appear in the server log.

Value Range Default Set Classifications
DEBUG5

DEBUG4

DEBUG3

DEBUG2

DEBUG1

INFO

NOTICE

WARNING

ERROR

FATAL

PANIC

ERROR master

session

reload

superuser

log_min_messages

Controls which message levels are written to the server log. Each level includes all the levels that follow it. The later the level, the fewer messages are sent to the log.

Value Range Default Set Classifications
DEBUG5

DEBUG4

DEBUG3

DEBUG2

DEBUG1

INFO

NOTICE

WARNING

LOG

ERROR

FATAL

PANIC

WARNING master

session

reload

superuser

log_parser_stats

For each query, write performance statistics of the query parser to the server log. This is a crude profiling instrument. Cannot be enabled together with log_statement_stats.

Value Range Default Set Classifications
Boolean off master

session

reload

superuser

log_planner_stats

For each query, write performance statistics of the legacy query optimizer (planner) to the server log. This is a crude profiling instrument. Cannot be enabled together with log_statement_stats.

Value Range Default Set Classifications
Boolean off master

session

reload

superuser

log_rotation_age

Determines the maximum lifetime of an individual log file. After this time has elapsed, a new log file will be created. Set to zero to disable time-based creation of new log files.

Value Range Default Set Classifications
Any valid time expression (number and unit) 1d local

system

restart

log_rotation_size

Determines the maximum size of an individual log file. After this many kilobytes have been emitted into a log file, a new log file will be created. Set to zero to disable size-based creation of new log files.

The maximum value is INT_MAX/1024. If an invalid value is specified, the default value is used. INT_MAX is the largest value that can be stored as an integer on your system.

Value Range Default Set Classifications
number of kilobytes 0 local

system

restart

log_statement

Controls which SQL statements are logged. DDL logs all data definition commands like CREATE, ALTER, and DROP commands. MOD logs all DDL statements, plus INSERT, UPDATE, DELETE, TRUNCATE, and COPY FROM. PREPARE and EXPLAIN ANALYZE statements are also logged if their contained command is of an appropriate type.

Value Range Default Set Classifications
NONE

DDL

MOD

ALL

ALL master

session

reload

superuser

log_statement_stats

For each query, write total performance statistics of the query parser, planner, and executor to the server log. This is a crude profiling instrument.

Value Range Default Set Classifications
Boolean off master

session

reload

superuser

log_timezone

Sets the time zone used for timestamps written in the log. Unlike TimeZone, this value is system-wide, so that all sessions will report timestamps consistently. The default is unknown, which means to use whatever the system environment specifies as the time zone.

Value Range Default Set Classifications
string unknown local

system

restart

log_truncate_on_rotation

Truncates (overwrites), rather than appends to, any existing log file of the same name. Truncation will occur only when a new file is being opened due to time-based rotation. For example, using this setting in combination with a log_filename such as gpseg#-%H.log would result in generating twenty-four hourly log files and then cyclically overwriting them. When off, pre-existing files will be appended to in all cases.

Value Range Default Set Classifications
Boolean off local

system

restart

max_appendonly_tables

Sets the maximum number of concurrent transactions that can write to or update append-optimized tables. Transactions that exceed the maximum return an error.

Operations that are counted are INSERT, UPDATE, COPY, and VACUUM operations. The limit is only for in-progress transactions. Once a transaction ends (either aborted or committed), it is no longer counted against this limit.

For operations against a partitioned table, each subpartition (child table) that is an append-optimized table and is changed counts as a single table towards the maximum. For example, a partitioned table p_tbl is defined with three subpartitions that are append-optimized tables p_tbl_ao1, p_tbl_ao2, and p_tbl_ao3. An INSERT or UPDATE command against the partitioned table p_tbl that changes append-optimized tables p_tbl_ao1 and p_tbl_ao2 is counted as two transactions.

Increasing the limit allocates more shared memory on the master host at server start.

Value Range Default Set Classifications
integer > 0 10000 master

system

restart

max_connections

The maximum number of concurrent connections to the database server. In a Greenplum Database system, user client connections go through the Greenplum master instance only. Segment instances should allow 5-10 times the amount as the master. When you increase this parameter, max_prepared_transactions must be increased as well. For more information about limiting concurrent connections, see "Configuring Client Authentication" in the Greenplum Database Administrator Guide.

Increasing this parameter may cause Greenplum Database to request more shared memory.Increasing this parameter might cause Greenplum Database to request more shared memory. See shared_buffers for information about Greenplum server instance shared memory buffers.

Value Range Default Set Classifications
10-n 250 on master

750 on segments

local

system

restart

max_files_per_process

Sets the maximum number of simultaneously open files allowed to each server subprocess. If the kernel is enforcing a safe per-process limit, you don't need to worry about this setting. Some platforms such as BSD, the kernel will allow individual processes to open many more files than the system can really support.

Value Range Default Set Classifications
integer 1000 local

system

restart

max_fsm_pages

Sets the maximum number of disk pages for which free space will be tracked in the shared free-space map. Six bytes of shared memory are consumed for each page slot.

Value Range Default Set Classifications
integer > 16 * max_fsm_relations 200000 local

system

restart

max_fsm_relations

Sets the maximum number of relations for which free space will be tracked in the shared memory free-space map. Should be set to a value larger than the total number of:

tables + indexes + system tables.

It costs about 60 bytes of memory for each relation per segment instance. It is better to allow some room for overhead and set too high rather than too low.

Value Range Default Set Classifications
integer 1000 local

system

restart

max_function_args

Reports the maximum number of function arguments.

Value Range Default Set Classifications
integer 100 read only

max_identifier_length

Reports the maximum identifier length.

Value Range Default Set Classifications
integer 63 read only

max_index_keys

Reports the maximum number of index keys.

Value Range Default Set Classifications
integer 32 read only

max_locks_per_transaction

The shared lock table is created with room to describe locks on max_locks_per_transaction * (max_connections + max_prepared_transactions) objects, so no more than this many distinct objects can be locked at any one time. This is not a hard limit on the number of locks taken by any one transaction, but rather a maximum average value. You might need to raise this value if you have clients that touch many different tables in a single transaction.

Value Range Default Set Classifications
integer 128 local

system

restart

max_prepared_transactions

Sets the maximum number of transactions that can be in the prepared state simultaneously. Greenplum uses prepared transactions internally to ensure data integrity across the segments. This value must be at least as large as the value of max_connections on the master. Segment instances should be set to the same value as the master.

Value Range Default Set Classifications
integer 250 on master

250 on segments

local

system

restart

max_resource_portals_per_transaction

Sets the maximum number of simultaneously open user-declared cursors allowed per transaction. Note that an open cursor will hold an active query slot in a resource queue. Used for workload management.

Value Range Default Set Classifications
integer 64 master

system

restart

max_resource_queues

Sets the maximum number of resource queues that can be created in a Greenplum Database system. Note that resource queues are system-wide (as are roles) so they apply to all databases in the system.

Value Range Default Set Classifications
integer 9 master

system

restart

max_stack_depth

Specifies the maximum safe depth of the server's execution stack. The ideal setting for this parameter is the actual stack size limit enforced by the kernel (as set by ulimit -s or local equivalent), less a safety margin of a megabyte or so. Setting the parameter higher than the actual kernel limit will mean that a runaway recursive function can crash an individual backend process.

Value Range Default Set Classifications
number of kilobytes 2MB local

system

restart

max_statement_mem

Sets the maximum memory limit for a query. Helps avoid out-of-memory errors on a segment host during query processing as a result of setting statement_mem too high. When gp_resqueue_memory_policy=auto, statement_mem and resource queue memory limits control query memory usage. Taking into account the configuration of a single segment host, calculate this setting as follows:

(seghost_physical_memory) / (average_number_concurrent_queries)

Value Range Default Set Classifications
number of kilobytes 2000MB master

session

reload

superuser

optimizer

Enables GPORCA when running SQL queries. The default is off, Greenplum Database uses only the legacy query optimizer.

GPORCA co-exists with the legacy query optimizer. When the Pivotal Query Optimizer is enabled, Greenplum Database uses GPORCA to generate an execution plan for a query when possible. If GPORCA cannot be used, the legacy query optimizer is used.

The optimizer parameter can be set for a database system, an individual database, or a session or query.

For information about the legacy query optimizer and GPORCA, see "Querying Data" in the Greenplum Database Administrator Guide.

Value Range Default Set Classifications
Boolean off master

session

reload

optimizer_analyze_root_partition

For a partitioned table, collects statistics for the root partition when the ANALYZE command is run on the table. GPORCA uses the root partition statistics when generating a query plan. The legacy query optimizer does not use these statistics. If you set the value of the server configuration parameter optimizer to on, set the value of this parameter to on and run the command ANALYZE or ANALYZE ROOTPARTITION on partitioned tables to ensure the proper statistics have been collected.

For information about the legacy query optimizer and GPORCA, see "Querying Data" in the Greenplum Database Administrator Guide.

Value Range Default Set Classifications
Boolean off master

session

reload

optimizer_array_expansion_threshold

When GPORCA is enabled and is processing a query that contains a predicate with a constant array, the optimizer_array_expansion_threshold parameter limits the optimization process based on the number of constants in the array. If the array in the query predicate contains more than the number elements specified by parameter, GPORCA disables the transformation of the predicate into its disjunctive normal form during query optimization.

The default value is 25.

For example, when GPORCA is executing a query that contains an IN clause with more than 25 elements, GPORCA does not transform the predicate into its disjunctive normal form during query optimization to reduce optimization time consume less memory. The difference in query processing can be seen in the filter condition for the IN clause of the query EXPLAIN plan.

Changing the value of this parameter changes the trade-off between a shorter optimization time and lower memory consumption, and the potential benefits from constraint derivation during query optimization, for example conflict detection and partition elimination.

The parameter can be set for a database system, an individual database, or a session or query.

Value Range Default Set Classifications
Integer > 0 25 master

session

reload

optimizer_control

Controls whether the server configuration parameter optimizer can be changed with SET, the RESET command, or the Greenplum Database utility gpconfig. If the optimizer_control parameter value is on, users can set the optimizer parameter. If the optimizer_control parameter value is off, the optimizer parameter cannot be changed.

Value Range Default Set Classifications
Boolean on master

system

restart

superuser

optimizer_cte_inlining_bound

When GPORCA is enabled, this parameter controls the amount of inlining performed for common table expression (CTE) queries (queries that contain a WITH clause). The default value, 0, disables inlining.

The parameter can be set for a database system, an individual database, or a session or query.

Value Range Default Set Classifications
Decimal >= 0 0 master

session

reload

optimizer_enable_master_only_queries

When GPORCA is enabled (the server configuration parameter optimizer is on), this parameter allows the Pivotal Query Optimizer to execute catalog queries that run only on the Greenplum Database master. For the default value off, only the legacy query optimizer can execute catalog queries that run only on the Greenplum Database master.

The parameter can be set for a database system, an individual database, or a session or query.

Note: Enabling this parameter decreases performance of short running catalog queries. To avoid this issue, set this parameter only for a session or a query.

For information about GPORCA, see the Greenplum Database Administrator Guide.

Value Range Default Set Classifications
Boolean off master

session

reload

optimizer_force_multistage_agg

When GPORCA is enabled, and this parameter is true, the default, GPORCA chooses a 3 stage aggregate plan for scalar distinct qualified aggregate when such a plan alternative is generated. When the value is false, GPORCA makes a cost based choice rather than a heuristic choice.

The parameter can be set for a database system, an individual database, or a session or query.

Value Range Default Set Classifications
Boolean true master

session

reload

optimizer_force_three_stage_scalar_dqa

When GPORCA is enabled and this parameter is true, the default, GPORCA chooses a plan with multistage aggregates when such a plan alternative is generated. When the value is false, GPORCA makes a cost based choice rather than a heuristic choice.

The parameter can be set for a database system, an individual database, or a session, or query.

Value Range Default Set Classifications
Boolean true master

session

reload

optimizer_join_order_threshold

When GPORCA is enabled, sets the maximum number of join children for which GPORCA will use the dynamic programming-based join ordering algorithm. You can set this value for a single query or for an entire session.

Value Range Default Set Classifications
0 - INT_MAX 10 master

session

reload

optimizer_minidump

GPORCA generates minidump files to describe the optimization context for a given query. The minidump files are used by Pivotal support to analyze Greenplum Database issues. The information in the file is not in a format that can be easily used by customers for debugging or troubleshooting. The minidump file is located under the master data directory and uses the following naming format:

Minidump_date_time.mdp

The minidump file contains this query related information:
  • Catalog objects including data types, tables, operators, and statistics required by GPORCA
  • An internal representation (DXL) of the query
  • An internal representation (DXL) of the plan produced by the Pivotal Query Optimizer
  • System configuration information passed to GPORCA such as server configuration parameters, cost and statistics configuration, and number of segments
  • A stack trace of errors generated while optimizing the query

Setting this parameter to ALWAYS generates a minidump for all queries. Set this parameter to ONERROR to minimize total optimization time.

For information about GPORCA, see "Querying Data" in the Greenplum Database Administrator Guide.

Value Range Default Set Classifications
ONERROR

ALWAYS

ONERROR master

session

reload

optimizer_nestloop_factor

When GPORCA is enabled, this parameter controls nested loop join cost factor to apply to during query optimization. The default value, 1, specifies the default sort cost factor. The value is a ratio of increase or decrease from the default factor. For example, a value of 2.0 sets the cost factor at twice the default, and a value of 0.5 sets the factor at half the default.

The parameter can be set for a database system, an individual database, or a session or query.

Value Range Default Set Classifications
Decimal > 0 1 master

session

reload

optimizer_parallel_union

When GPORCA is enabled, optimizer_parallel_union controls the amount of parallelization that occurs for queries that contain a UNION or UNION ALL clause.

When the value is off, the default, GPORCA generates a query plan where each child of an APPEND(UNION) operator is in the same slice as the APPEND operator. During query execution, the children are executed in a sequential manner.

When the value is on, GPORCA generates a query plan where a redistribution motion node is under an APPEND(UNION) operator. During query execution, the children and the parent APPEND operator are on different slices, allowing the children of the APPEND(UNION) operator to execute in parallel on segment instances.

The parameter can be set for a database system, an individual database, or a session or query.

Value Range Default Set Classifications
boolean off master

session

reload

optimizer_print_missing_stats

When GPORCA is enabled, this parameter controls the display of table column information about columns with missing statistics for a query. The default value is true, display the column information to the client. When the value is false, the information is not sent to the client.

The information is displayed during query execution, or with the EXPLAIN or EXPLAIN ANALYZE commands.

The parameter can be set for a database system, an individual database, or a session.

Value Range Default Set Classifications
Boolean true master

session

reload

optimizer_print_optimization_stats

When GPORCA is enabled, this parameter enables logging of GPORCA query optimization statistics for various optimization stages for a query. The default value is off, do not log optimization statistics. To log the optimization statistics, this parameter must be set to on and the parameter client_min_messages must be set to log.
  • set optimizer_print_optimization_stats = on;
  • set client_min_messages = 'log';

The information is logged during query execution, or with the EXPLAIN or EXPLAIN ANALYZE commands.

This parameter can be set for a database system, an individual database,or a session or query.

Value Range Default Set Classifications
Boolean off master

session

reload

optimizer_sort_factor

When GPORCA is enabled, optimizer_sort_factor controls the cost factor to apply to sorting operations during query optimization. The default value 1 specifies the default sort cost factor. The value is a ratio of increase or decrease from the default factor. For example, a value of 2.0 sets the cost factor at twice the default, and a value of 0.5 sets the factor at half the default.

The parameter can be set for a database system, an individual database, or a session or query.

Value Range Default Set Classifications
Decimal > 0 1 master

session

reload

password_encryption

When a password is specified in CREATE USER or ALTER USER without writing either ENCRYPTED or UNENCRYPTED, this option determines whether the password is to be encrypted.

Value Range Default Set Classifications
Boolean on master

session

reload

password_hash_algorithm

Specifies the cryptographic hash algorithm that is used when storing an encrypted Greenplum Database user password. The default algorithm is MD5.

For information about setting the password hash algorithm to protect user passwords, see "Protecting Passwords in Greenplum Database" in the Greenplum Database Administrator Guide.

Value Range Default Set Classifications
MD5

SHA-256

SHA-256-FIPS

MD5 master

session

reload

superuser

pgcrypto.fips

Enables support for Federal Information Processing Standard (FIPS) 140-2. For information about FIPS, see https://www.nist.gov/itl/popular-links/federal-information-processing-standards-fips

Note: This parameter is deprecated. Greenplum Database support for Federal Information Processing Standard (FIPS) in the Greenplum Database pgcrypto extension is deprecated. Support for FIPS and this parameter will be removed in a future release.
To enable FIPS 140-2 support for Greenplum Database, the following are required.
  • The Greenplum Database pgcrypto package version 1.2 or later must be installed.
  • If the value of pgcrypto.fips is set to on, the value of the parameter custom_variable_classes must contain pgcrypto.
When FIPS 140-2 support is enabled, these pgcrypto changes occur:
  • FIPS mode is initialized in the OpenSSL library
  • The functions digest() and hmac() allow only the SHA encryption algorithm (MD5 is not allowed)
  • The functions for crypt and gen_salt algorithms are disabled
  • PGP encryption and decryption functions support only AES and 3DES encryption algorithms (other algorithms such as blowfish are not allowed)
  • RAW encryption and decryption functions support only AES and 3DES (other algorithms such as blowfish are not allowed)
These gpconfig commands set the parameters to enable FIPS 140-2 support.
$ gpconfig -c custom_variable_classes -v pgcrypto --masteronly
$ gpconfig -c pgcrypto.fips -v on --masteronly
The value of the custom_variable_classes parameter is a comma separated list of classes. For more than one class, the list is inclosed in single quotes. To check the value of the parameter use gpconfig with the -s option to show the current value.
$ gpconfig -s custom_variable_classes
If the parameter is already set with custom classes, you can add pgcrypto. For example, if the value of custom_variable_classes is plr, this command adds pgcrypto.
$ gpconfig -c custom_variable_classes -v \'plr,pgcrypto\' --masteronly  
   --skipvalidation

In the command, use a backslash (\) to escape the single quotes.

Value Range Default Set Classifications
Boolean off master

system

restart

pgstat_track_activity_query_size

Sets the maximum length limit for the query text stored in current_query column of the system catalog view pg_stat_activity. The minimum length is 1024 characters.

Value Range Default Set Classifications
integer 1024 local

system

restart

pljava_classpath

A colon (:) separated list of jar files or directories containing jar files needed for PL/Java functions. The full path to the jar file or directory must be specified, except the path can be omitted for jar files in the $GPHOME/lib/postgresql/java directory. The jar files must be installed in the same locations on all Greenplum hosts and readable by the gpadmin user.

The pljava_classpath parameter is used to assemble the PL/Java classpath at the beginning of each user session. Jar files added after a session has started are not available to that session.

If the full path to a jar file is specified in pljava_classpath it is added to the PL/Java classpath. When a directory is specified, any jar files the directory contains are added to the PL/Java classpath. The search does not descend into subdirectories of the specified directories. If the name of a jar file is included in pljava_classpath with no path, the jar file must be in the $GPHOME/lib/postgresql/java directory.

Note: Performance can be affected if there are many directories to search or a large number of jar files.

If pljava_classpath_insecure is false, setting the pljava_classpath parameter requires superuser privilege. Setting the classpath in SQL code will fail when the code is executed by a user without superuser privilege. The pljava_classpath parameter must have been set previously by a superuser or in the postgresql.conf file. Changing the classpath in the postgresql.conf file requires a reload (gpstop -u).

Value Range Default Set Classifications
string   master

session

restart

superuser

pljava_classpath_insecure

Controls whether the server configuration parameter pljava_classpath can be set by a user without Greenplum Database superuser privileges. When true, pljava_classpath can be set by a regular user. Otherwise, pljava_classpath can be set only by a database superuser. The default is false.

Warning: Enabling this parameter exposes a security risk by giving non-administrator database users the ability to run unauthorized Java methods.
Value Range Default Set Classifications
Boolean false master

session

restart

superuser

pljava_statement_cache_size

Sets the size in KB of the JRE MRU (Most Recently Used) cache for prepared statements.

Value Range Default Set Classifications
number of kilobytes 10 master

system

restart

superuser

pljava_release_lingering_savepoints

If true, lingering savepoints used in PL/Java functions will be released on function exit. If false, savepoints will be rolled back.

Value Range Default Set Classifications
Boolean true master

system

restart

superuser

pljava_vmoptions

Defines the startup options for the Java VM. The default value is an empty string ("").

Value Range Default Set Classifications
string   master

system

restart

superuser

port

The database listener port for a Greenplum instance. The master and each segment has its own port. Port numbers for the Greenplum system must also be changed in the gp_segment_configuration catalog. You must shut down your Greenplum Database system before changing port numbers.

Value Range Default Set Classifications
any valid port number 5432 local

system

restart

random_page_cost

Sets the estimate of the cost of a nonsequentially fetched disk page for the legacy query optimizer (planner). This is measured as a multiple of the cost of a sequential page fetch. A higher value makes it more likely a sequential scan will be used, a lower value makes it more likely an index scan will be used.

Value Range Default Set Classifications
floating point 100 master

session

reload

readable_external_table_timeout

When an SQL query reads from an external table, the parameter value specifies the amount of time in seconds that Greenplum Database waits before cancelling the query when data stops being returned from the external table.

The default value of 0, specifies no time out. Greenplum Database does not cancel the query.

If queries that use gpfdist run a long time and then return the error "intermittent network connectivity issues", you can specify a value for readable_external_table_timeout. If no data is returned by gpfdist for the specified length of time, Greenplum Database cancels the query.

Value Range Default Set Classifications
integer >= 0 0 master

system

reload

repl_catchup_within_range

For Greenplum Database master mirroring, controls updates to the active master. If the number of WAL segment files that have not been processed by the walsender exceeds this value, Greenplum Database updates the active master.

If the number of segment files does not exceed the value, Greenplum Database blocks updates to the to allow the walsender process the files. If all WAL segments have been processed, the active master is updated.

Value Range Default Set Classifications
0 - 64 1 master

system

reload

superuser

replication_timeout

For Greenplum Database master mirroring, sets the maximum time in milliseconds that the walsender process on the active master waits for a status message from the walreceiver process on the standby master. If a message is not received, the walsender logs an error message.

The wal_receiver_status_interval controls the interval between walreceiver status messages.

Value Range Default Set Classifications
0 - INT_MAX 60000 ms (60 seconds) master

system

reload

superuser

regex_flavor

The 'extended' setting may be useful for exact backwards compatibility with pre-7.4 releases of PostgreSQL.

Value Range Default Set Classifications
advanced

extended

basic

advanced master

session

reload

resource_cleanup_gangs_on_wait

If a statement is submitted through a resource queue, clean up any idle query executor worker processes before taking a lock on the resource queue.

Value Range Default Set Classifications
Boolean on master

system

restart

resource_select_only

Sets the types of queries managed by resource queues. If set to on, then SELECT, SELECT INTO, CREATE TABLE AS SELECT, and DECLARE CURSOR commands are evaluated. If set to off INSERT, UPDATE, and DELETE commands will be evaluated as well.

Value Range Default Set Classifications
Boolean off master

system

restart

runaway_detector_activation_percent

Sets the percentage of Greenplum Database vmem memory that triggers the termination of queries. If the percentage of vmem memory that is utilized for a Greenplum Database segment exceeds the specified value, Greenplum Database terminates queries based on memory usage, starting with the query consuming the largest amount of memory. Queries are terminated until the percentage of utilized vmem is below the specified percentage.

Specify the maximum vmem value for active Greenplum Database segment instances with the server configuration parameter gp_vmem_protect_limit.

For example, if vmem memory is set to 10GB, and the value of runaway_detector_activation_percent is 90 (90%), Greenplum Database starts terminating queries when the utilized vmem memory exceeds 9 GB.

A value of 0 disables the automatic termination of queries based on percentage of vmem that is utilized.

Value Range Default Set Classifications
percentage (integer) 90 local

system

restart

search_path

Specifies the order in which schemas are searched when an object is referenced by a simple name with no schema component. When there are objects of identical names in different schemas, the one found first in the search path is used. The system catalog schema, pg_catalog, is always searched, whether it is mentioned in the path or not. When objects are created without specifying a particular target schema, they will be placed in the first schema listed in the search path. The current effective value of the search path can be examined via the SQL function current_schemas(). current_schemas() shows how the requests appearing in search_path were resolved.

Value Range Default Set Classifications
a comma- separated list of schema names $user,public master

session

reload

seq_page_cost

For the legacy query optimizer (planner), sets the estimate of the cost of a disk page fetch that is part of a series of sequential fetches.

Value Range Default Set Classifications
floating point 1 master

session

reload

server_encoding

Reports the database encoding (character set). It is determined when the Greenplum Database array is initialized. Ordinarily, clients need only be concerned with the value of client_encoding.

Value Range Default Set Classifications
<system dependent> UTF8 read only

server_version

Reports the version of PostgreSQL that this release of Greenplum Database is based on.

Value Range Default Set Classifications
string 8.2.15 read only

server_version_num

Reports the version of PostgreSQL that this release of Greenplum Database is based on as an integer.

Value Range Default Set Classifications
integer 80215 read only

shared_buffers

Sets the amount of memory a Greenplum Database segment instance uses for shared memory buffers. This setting must be at least 128KB and at least 16KB times max_connections.

Each Greenplum Database segment instance calculates and attempts to allocate certain amount of shared memory based on the segment configuration. The value of shared_buffers is significant portion of this shared memory calculation, but is not all it. When setting shared_buffers, the values for the operating system parameters SHMMAX or SHMALL might also need to be adjusted.

The operating system parameter SHMMAX specifies maximum size of a single shared memory allocation. The value of SHMMAX must be greater than this value:
 shared_buffers + other_seg_shmem
The value of other_seg_shmem is the portion the Greenplum Database shared memory calculation that is not accounted for by the shared_buffers value. The other_seg_shmem value will vary based on the segment configuration.

With the default Greenplum Database parameter values, the value for other_seg_shmem is approximately 111MB for Greenplum Database segments and approximately 79MB for the Greenplum Database master.

The operating system parameter SHMALL specifies the maximum amount of shared memory on the host. The value of SHMALL must be greater than this value:
 (num_instances_per_host * ( shared_buffers + other_seg_shmem )) + other_app_shared_mem 
The value of other_app_shared_mem is the amount of shared memory that is used by other applications and processes on the host.

When shared memory allocation errors occur, possible ways to resolve shared memory allocation issues are to increase SHMMAX or SHMALL, or decrease shared_buffers or max_connections.

See the Greenplum Database Installation Guide for information about the Greenplum Database values for the parameters SHMMAX and SHMALL.

Value Range Default Set Classifications
integer > 16K * max_connections 125MB local

system

restart

shared_preload_libraries

A comma-separated list of shared libraries that are to be preloaded at server start. PostgreSQL procedural language libraries can be preloaded in this way, typically by using the syntax '$libdir/plXXX' where XXX is pgsql, perl, tcl, or python. By preloading a shared library, the library startup time is avoided when the library is first used. If a specified library is not found, the server will fail to start.

Value Range Default Set Classifications
    local

system

restart

ssl

Enables SSL connections.

Value Range Default Set Classifications
Boolean off master

system

restart

ssl_ciphers

Specifies a list of SSL ciphers that are allowed to be used on secure connections. See the openssl manual page for a list of supported ciphers.

Value Range Default Set Classifications
string ALL master

system

restart

standard_conforming_strings

Determines whether ordinary string literals ('...') treat backslashes literally, as specified in the SQL standard. The default value is off, indicating that backslashes are treated as escapes. It is planned that this will change to on in a future release when string literal syntax changes to meet the standard. Applications can check this parameter to determine how string literals will be processed. The presence of this parameter can also be taken as an indication that the escape string syntax (E'...') is supported.

Value Range Default Set Classifications
Boolean off master

session

reload

statement_mem

Allocates segment host memory per query. The amount of memory allocated with this parameter cannot exceed max_statement_mem or the memory limit on the resource queue through which the query was submitted. When gp_resqueue_memory_policy =auto, statement_mem and resource queue memory limits control query memory usage.

If additional memory is required for a query, temporary spill files on disk are used.

This calculation can be used to estimate a reasonable value for a wide variety of situations.

( gp_vmem_protect_limitGB * .9 ) / max_expected_concurrent_queries

With the gp_vmem_protect_limit set to 8192MB (8GB) and assuming a maximum of 40 concurrent queries with a 10% buffer

(8GB * .9) / 40 = .18GB = 184MB
Value Range Default Set Classifications
number of kilobytes 128MB master

session

reload

statement_timeout

Abort any statement that takes over the specified number of milliseconds. 0 turns off the limitation.

Value Range Default Set Classifications
number of milliseconds 0 master

session

reload

stats_queue_level

Collects resource queue statistics on database activity.

Value Range Default Set Classifications
Boolean off master

session

reload

superuser_reserved_connections

Determines the number of connection slots that are reserved for Greenplum Database superusers.

Value Range Default Set Classifications
integer < max_connections 3 local

system

restart

tcp_keepalives_count

How many keepalives may be lost before the connection is considered dead. A value of 0 uses the system default. If TCP_KEEPCNT is not supported, this parameter must be 0.

Use this parameter for all connections that are not between a primary and mirror segment. Use gp_filerep_tcp_keepalives_count for settings that are between a primary and mirror segment.

Value Range Default Set Classifications
number of lost keepalives 0 local

system

restart

tcp_keepalives_idle

Number of seconds between sending keepalives on an otherwise idle connection. A value of 0 uses the system default. If TCP_KEEPIDLE is not supported, this parameter must be 0.

Use this parameter for all connections that are not between a primary and mirror segment. Use gp_filerep_tcp_keepalives_idle for settings that are between a primary and mirror segment.

Value Range Default Set Classifications
number of seconds 0 local

system

restart

tcp_keepalives_interval

How many seconds to wait for a response to a keepalive before retransmitting. A value of 0 uses the system default. If TCP_KEEPINTVL is not supported, this parameter must be 0.

Use this parameter for all connections that are not between a primary and mirror segment. Use gp_filerep_tcp_keepalives_interval for settings that are between a primary and mirror segment.

Value Range Default Set Classifications
number of seconds 0 local

system

restart

temp_buffers

Sets the maximum number of temporary buffers used by each database session. These are session-local buffers used only for access to temporary tables. The setting can be changed within individual sessions, but only up until the first use of temporary tables within a session. The cost of setting a large value in sessions that do not actually need a lot of temporary buffers is only a buffer descriptor, or about 64 bytes, per increment. However if a buffer is actually used, an additional 8192 bytes will be consumed.

Value Range Default Set Classifications
integer 1024 master

session

reload

TimeZone

Sets the time zone for displaying and interpreting time stamps. The default is to use whatever the system environment specifies as the time zone. See Date/Time Keywords in the PostgreSQL documentation.

Value Range Default Set Classifications
time zone abbreviation   local

restart

timezone_abbreviations

Sets the collection of time zone abbreviations that will be accepted by the server for date time input. The default is Default, which is a collection that works in most of the world. Australia and India, and other collections can be defined for a particular installation. Possible values are names of configuration files stored in $GPHOME/share/postgresql/timezonesets/.

To configure Greenplum Database to use a custom collection of timezones, copy the file that contains the timezone definitions to the directory $GPHOME/share/postgresql/timezonesets/ on the Greenplum Database master and segment hosts. Then set value of the server configuration parameter timezone_abbreviations to the file. For example, to use a file custom that contains the default timezones and the WIB (Waktu Indonesia Barat) timezone.

  1. Copy the file Default from the directory $GPHOME/share/postgresql/timezonesets/ the file custom. Add the WIB timezone information from the file Asia.txt to the custom.
  2. Copy the file custom to the directory $GPHOME/share/postgresql/timezonesets/ on the Greenplum Database master and segment hosts.
  3. Set value of the server configuration parameter timezone_abbreviations to custom.
  4. Reload the server configuration file (gpstop -u).
Value Range Default Set Classifications
string Default master

session

reload

track_activities

Enables the collection of statistics on the currently executing command of each session, along with the time at which that command began execution. When enabled, this information is not visible to all users, only to superusers and the user owning the session. This data can be accessed via the pg_stat_activity system view.

Value Range Default Set Classifications
Boolean on master

session

reload

track_counts

Enables the collection of row and block level statistics on database activity. If enabled, the data that is produced can be accessed via the pg_stat and pg_statio family of system views.

Value Range Default Set Classifications
Boolean off local

system

restart

transaction_isolation

Sets the current transaction's isolation level.

Value Range Default Set Classifications
read committed

serializable

read committed master

session

reload

transaction_read_only

Sets the current transaction's read-only status.

Value Range Default Set Classifications
Boolean off master

session

reload

transform_null_equals

When on, expressions of the form expr = NULL (or NULL = expr) are treated as expr IS NULL, that is, they return true if expr evaluates to the null value, and false otherwise. The correct SQL-spec-compliant behavior of expr = NULL is to always return null (unknown).

Value Range Default Set Classifications
Boolean off master

session

reload

unix_socket_directory

Specifies the directory of the UNIX-domain socket on which the server is to listen for connections from client applications.

Value Range Default Set Classifications
directory path unset local

system

restart

unix_socket_group

Sets the owning group of the UNIX-domain socket. By default this is an empty string, which uses the default group for the current user.

Value Range Default Set Classifications
UNIX group name unset local

system

restart

unix_socket_permissions

Sets the access permissions of the UNIX-domain socket. UNIX-domain sockets use the usual UNIX file system permission set. Note that for a UNIX-domain socket, only write permission matters.

Value Range Default Set Classifications
numeric UNIX file permission mode (as accepted by the chmod or umask commands) 511 local

system

restart

update_process_title

Enables updating of the process title every time a new SQL command is received by the server. The process title is typically viewed by the ps command.

Value Range Default Set Classifications
Boolean on local

system

restart

vacuum_cost_delay

The length of time that the process will sleep when the cost limit has been exceeded. 0 disables the cost-based vacuum delay feature.

Value Range Default Set Classifications
milliseconds < 0 (in multiples of 10) 0 local

system

restart

vacuum_cost_limit

The accumulated cost that will cause the vacuuming process to sleep.

Value Range Default Set Classifications
integer > 0 200 local

system

restart

vacuum_cost_page_dirty

The estimated cost charged when vacuum modifies a block that was previously clean. It represents the extra I/O required to flush the dirty block out to disk again.

Value Range Default Set Classifications
integer > 0 20 local

system

restart

vacuum_cost_page_hit

The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of the page.

Value Range Default Set Classifications
integer > 0 1 local

system

restart

vacuum_cost_page_miss

The estimated cost for vacuuming a buffer that has to be read from disk. This represents the effort to lock the buffer pool, lookup the shared hash table, read the desired block in from the disk and scan its content.

Value Range Default Set Classifications
integer > 0 10 local

system

restart

vacuum_freeze_min_age

Specifies the cutoff age (in transactions) that VACUUM should use to decide whether to replace transaction IDs with FrozenXID while scanning a table.

For information about VACUUM and transaction ID management, see "Managing Data" in the Greenplum Database Administrator Guide and the PostgreSQL documentation.

Value Range Default Set Classifications
integer 0-100000000000 100000000 local

system

restart

validate_previous_free_tid

Enables a test that validates the free tuple ID (TID) list. The list is maintained and used by Greenplum Database. Greenplum Database determines the validity of the free TID list by ensuring the previous free TID of the current free tuple is a valid free tuple. The default value is true, enable the test.

If Greenplum Database detects a corruption in the free TID list, the free TID list is rebuilt, a warning is logged, and a warning is returned by queries for which the check failed. Greenplum Database attempts to execute the queries. If a warning is returned, please contact Pivotal Support.

Value Range Default Set Classifications
Boolean true master

session

reload

vmem_process_interrupt

Enables checking for interrupts before reserving vmem memory for a query during Greenplum Database query execution. Before reserving further vmem for a query, check if the current session for the query has a pending query cancellation or other pending interrupts. This ensures more responsive interrupt processing, including query cancellation requests. The default is off.

Value Range Default Set Classifications
Boolean off master

session

reload

wal_receiver_status_interval

For Greenplum Database master mirroring, sets the interval in seconds between walreceiver process status messages that are sent to the active master. Under heavy loads, the time might be longer.

The value of replication_timeout controls the time that the walsender process waits for a walreceiver message.

Value Range Default Set Classifications
integer 0- INT_MAX/1000 10 sec master

system

reload

superuser

writable_external_table_bufsize

Size of the buffer (in KB) that Greenplum Database uses for network communication, such as the gpfdist utility and external web tables (that use http). Greenplum Database stores data in the buffer before writing the data out. For information about gpfdist, see the Greenplum Database Utility Guide.

Value Range Default Set Classifications
integer 32 - 131072 (32KB - 128MB) 64 local

system

reload

xid_stop_limit

The number of transaction IDs prior to the ID where transaction ID wraparound occurs. When this limit is reached, Greenplum Database stops creating new transactions to avoid data loss due to transaction ID wraparound.

Value Range Default Set Classifications
integer 10000000 - 2000000000 1000000000 local

system

restart

xid_warn_limit

The number of transaction IDs prior to the limit specified by xid_stop_limit. When Greenplum Database reaches this limit, it issues a warning to perform a VACUUM operation to avoid data loss due to transaction ID wraparound.

Value Range Default Set Classifications
integer 10000000 - 2000000000 500000000 local

system

restart