COPY

COPY

Copies data between a file and a table.

Synopsis

COPY table [(column [, ...])] FROM {'file' | STDIN}
     [ [WITH] 
       [OIDS]
       [HEADER]
       [DELIMITER [ AS ] 'delimiter']
       [NULL [ AS ] 'null string']
       [ESCAPE [ AS ] 'escape' | 'OFF']
       [NEWLINE [ AS ] 'LF' | 'CR' | 'CRLF']
       [CSV [QUOTE [ AS ] 'quote'] 
            [FORCE NOT NULL column [, ...]]
       [FILL MISSING FIELDS]
       [[LOG ERRORS [INTO error_table] [KEEP] 
       SEGMENT REJECT LIMIT count [ROWS | PERCENT] ]

COPY {table [(column [, ...])] | (query)} TO {'file' | STDOUT}
      [ [WITH] 
        [OIDS]
        [HEADER]
        [DELIMITER [ AS ] 'delimiter']
        [NULL [ AS ] 'null string']
        [ESCAPE [ AS ] 'escape' | 'OFF']
        [CSV [QUOTE [ AS ] 'quote'] 
             [FORCE QUOTE column [, ...]] ]
      [IGNORE EXTERNAL PARTITIONS ]

Description

COPY moves data between Greenplum Database tables and standard file-system files. COPY TO copies the contents of a table to a file, while COPY FROM copies data from a file to a table (appending the data to whatever is in the table already). COPY TO can also copy the results of a SELECT query.

If a list of columns is specified, COPY will only copy the data in the specified columns to or from the file. If there are any columns in the table that are not in the column list, COPY FROM will insert the default values for those columns.

COPY with a file name instructs the Greenplum Database master host to directly read from or write to a file. The file must be accessible to the master host and the name must be specified from the viewpoint of the master host. When STDIN or STDOUT is specified, data is transmitted via the connection between the client and the master.

If SEGMENT REJECT LIMIT is used, then a COPY FROM operation will operate in single row error isolation mode. In this release, single row error isolation mode only applies to rows in the input file with format errors — for example, extra or missing attributes, attributes of a wrong data type, or invalid client encoding sequences. Constraint errors such as violation of a NOT NULL, CHECK, or UNIQUE constraint will still be handled in 'all-or-nothing' input mode. The user can specify the number of error rows acceptable (on a per-segment basis), after which the entire COPY FROM operation will be aborted and no rows will be loaded. Note that the count of error rows is per-segment, not per entire load operation. If the per-segment reject limit is not reached, then all rows not containing an error will be loaded. If the limit is not reached, all good rows will be loaded and any error rows discarded. If you would like to keep error rows for further examination, you can optionally declare an error table using the LOG ERRORS INTO clause. Any rows containing a format error would then be logged to the specified error table.

Outputs

On successful completion, a COPY command returns a command tag of the form, where count is the number of rows copied:

COPY count

If running a COPY FROM command in single row error isolation mode, the following notice message will be returned if any rows were not loaded due to format errors, where count is the number of rows rejected:

NOTICE: Rejected count badly formatted rows.

Parameters

table
The name (optionally schema-qualified) of an existing table.
column
An optional list of columns to be copied. If no column list is specified, all columns of the table will be copied.
For a column of type bytea, a row of data can be up to 256MB.
query
A SELECT or VALUES command whose results are to be copied. Note that parentheses are required around the query.
file
The absolute path name of the input or output file.
STDIN
Specifies that input comes from the client application.
STDOUT
Specifies that output goes to the client application.
OIDS
Specifies copying the OID for each row. (An error is raised if OIDS is specified for a table that does not have OIDs, or in the case of copying a query.)
delimiter
The single ASCII character that separates columns within each row (line) of the file. The default is a tab character in text mode, a comma in CSV mode.
null string
The string that represents a null value. The default is \N (backslash-N) in text mode, and a empty value with no quotes in CSV mode. You might prefer an empty string even in text mode for cases where you don't want to distinguish nulls from empty strings. When using COPY FROM, any data item that matches this string will be stored as a null value, so you should make sure that you use the same string as you used with COPY TO.
escape
Specifies the single character that is used for C escape sequences (such as \n,\t,\100, and so on) and for quoting data characters that might otherwise be taken as row or column delimiters. Make sure to choose an escape character that is not used anywhere in your actual column data. The default escape character is \ (backslash) for text files or " (double quote) for CSV files, however it is possible to specify any other character to represent an escape. It is also possible to disable escaping on text-formatted files by specifying the value 'OFF' as the escape value. This is very useful for data such as web log data that has many embedded backslashes that are not intended to be escapes.
NEWLINE
Specifies the newline used in your data files — LF (Line feed, 0x0A), CR (Carriage return, 0x0D), or CRLF (Carriage return plus line feed, 0x0D 0x0A). If not specified, a Greenplum Database segment will detect the newline type by looking at the first row of data it receives and using the first newline type encountered.
CSV
Selects Comma Separated Value (CSV) mode. SeeCSV Format.
HEADER
Specifies that a file contains a header line with the names of each column in the file. On output, the first line contains the column names from the table, and on input, the first line is ignored.
quote
Specifies the quotation character in CSV mode. The default is double-quote.
FORCE QUOTE
In CSV COPY TO mode, forces quoting to be used for all non-NULL values in each specified column. NULL output is never quoted.
FORCE NOT NULL
In CSV COPY FROM mode, process each specified column as though it were quoted and hence not a NULL value. For the default null string in CSV mode (nothing between two delimiters), this causes missing values to be evaluated as zero-length strings.
FILL MISSING FIELDS
In COPY FROM more for both TEXT and CSV, specifying FILL MISSING FIELDS will set missing trailing field values to NULL (instead of reporting an error) when a row of data has missing data fields at the end of a line or row. Blank rows, fields with a NOT NULL constraint, and trailing delimiters on a line will still report an error.
LOG ERRORS [INTO error_table] [KEEP]
This is an optional clause that can precede a SEGMENT REJECT LIMIT clause to log information about rows with formatting errors. The INTO error_table clause specifies an error table where rows with formatting errors will be logged when running in single row error isolation mode.
If the INTO error_table clause is not specified, the error log information is stored internally (not in an error table). Error log information that is stored internally is accessed with the Greenplum Database built-in SQL function gp_read_error_log().
If the error_table specified already exists, it is used. If it does not exist, it is created. If error_table exists and does not have a random distribution (the DISTRIBUTED RANDOMLY clause was not specified when creating the table), an error is returned.
If the command generates the error table and no errors are produced, the default is to drop the error table after the operation completes unless KEEP is specified. If the table is created and the error limit is exceeded, the entire transaction is rolled back and no error data is saved. If you want the error table to persist in this case, create the error table prior to running the COPY.
See Notes for information about the error log information and built-in functions for viewing and managing error log information.
Note: The optional INTO error_table clause is deprecated and will not be supported in a future release. Only internal error logs will be supported.
SEGMENT REJECT LIMIT count [ROWS | PERCENT]
Runs a COPY FROM operation in single row error isolation mode. If the input rows have format errors they will be discarded provided that the reject limit count is not reached on any Greenplum Database segment instance during the load operation. The reject limit count can be specified as number of rows (the default) or percentage of total rows (1-100). If PERCENT is used, each segment starts calculating the bad row percentage only after the number of rows specified by the parameter gp_reject_percent_threshold has been processed. The default for gp_reject_percent_threshold is 300 rows. Constraint errors such as violation of a NOT NULL, CHECK, or UNIQUE constraint will still be handled in 'all-or-nothing' input mode. If the limit is not reached, all good rows will be loaded and any error rows discarded.
Note: Greenplum Database limits the initial number of rows that can contain formatting errors if the SEGMENT REJECT LIMIT is not triggered first or is not specified. If the first 1000 rows are rejected, the COPY operation is stopped and rolled back.

The limit for the number of initial rejected rows can be changed with the Greenplum Database server configuration parameter gp_initial_bad_row_limit. See Server Configuration Parameters for information about the parameter.

IGNORE EXTERNAL PARTITIONS
When copying data from partitioned tables, data are not copied from leaf child partitions that are external tables. A message is added to the log file when data are not copied.
If this clause is not specified and Greenplum Database attempts to copy data from a leaf child partition that is an external table, an error is returned.
See the next section "Notes" for information about specifying an SQL query to copy data from leaf child partitions that are external tables.

Notes

COPY can only be used with tables, not with external tables or views. However, you can write COPY (SELECT * FROM viewname) TO ...

To copy data from a partitioned table with a leaf child partition that is an external table, use an SQL query to copy the data. For example, if the table my_sales contains a with a leaf child partition that is an external table, this command COPY my_sales TO stdout returns an error. This command sends the data to stdout:
COPY (SELECT * from my_sales ) TO stdout

You must have SELECT privilege on the table whose values are read by COPY TO, and insert privilege on the table into which values are inserted by COPY FROM.

Files named in a COPY command are read or written directly by the database server, not by the client application. Therefore, they must reside on or be accessible to the Greenplum Database master host machine, not the client. They must be accessible to and readable or writable by the Greenplum Database system user (the user ID the server runs as), not the client. COPY naming a file is only allowed to database superusers, since it allows reading or writing any file that the server has privileges to access.

COPY FROM will invoke any triggers and check constraints on the destination table. However, it will not invoke rewrite rules. Note that in this release, violations of constraints are not evaluated for single row error isolation mode.

COPY input and output is affected by DateStyle. To ensure portability to other Greenplum Database installations that might use non-default DateStyle settings, DateStyle should be set to ISO before using COPY TO.

When copying XML data from a file, COPY returns an error if the XML data is not a valid XML document.

By default, COPY stops operation at the first error. This should not lead to problems in the event of a COPY TO, but the target table will already have received earlier rows in a COPY FROM. These rows will not be visible or accessible, but they still occupy disk space. This may amount to a considerable amount of wasted disk space if the failure happened well into a large COPY FROM operation. You may wish to invoke VACUUM to recover the wasted space. Another option would be to use single row error isolation mode to filter out error rows while still loading good rows.

When you specify LOG ERRORS INTO error_table, Greenplum Database creates the table error_table that contains errors that occur while reading the external table. The table is defined as follows:
CREATE TABLE error_table_name ( cmdtime timestamptz, relname text, 
    filename text, linenum int, bytenum int, errmsg text, 
    rawdata text, rawbytes bytea ) DISTRIBUTED RANDOMLY;

You can view the information in the table with SQL commands.

For error log data that is stored internally when the INTO error_table is not specified:
  • Use the built-in SQL function gp_read_error_log('table_name'). It requires SELECT privilege on table_name. This example displays the error log information for data loaded into table ext_expenses with a COPY command:
    SELECT * from gp_read_error_log('ext_expenses');

    The error log contains the same columns as the error table.

    The function returns FALSE if table_name does not exist.

  • If error log data exists for the specified table, the new error log data is appended to existing error log data. The error log information is not replicated to mirror segments.
  • Use the built-in SQL function gp_truncate_error_log('table_name') to delete the error log data for table_name. It requires the table owner privilege This example deletes the error log information captured when moving data into the table ext_expenses:
    SELECT gp_truncate_error_log('ext_expenses'); 

    The function returns FALSE if table_name does not exist.

    Specify the * wildcard character to delete error log information for existing tables in the current database. Specify the string *.* to delete all database error log information, including error log information that was not deleted due to previous database issues. If * is specified, database owner privilege is required. If *.* is specified, operating system super-user privilege is required.

When a Greenplum Database user who is not a superuser runs a COPY command, the command can be controlled by a resource queue. The resource queue must be configured with the ACTIVE_STATEMENTS parameter that specifies a maximum limit on the number of queries that can be executed by roles assigned to that queue. Greenplum Database does not apply a cost value or memory value to a COPY command, resource queues with only cost or memory limits do not affect the running of COPY commands.

A non-superuser can runs can run these types of COPY commands:
  • COPY FROM command where the source is stdin
  • COPY TO command where the destination is stdout

For information about resource queues, see "Workload Management with Resource Queues" in the Greenplum Database Administrator Guide.

File Formats

File formats supported by COPY.

Text Format

When COPY is used without the CSV, the data read or written is a text file with one line per table row. Columns in a row are separated by the delimiter character (tab by default). The column values themselves are strings generated by the output function, or acceptable to the input function, of each attribute's data type. The specified null string is used in place of columns that are null. COPY FROM will raise an error if any line of the input file contains more or fewer columns than are expected. If OIDS is specified, the OID is read or written as the first column, preceding the user data columns.

The data file has two reserved characters that have special meaning to COPY:

  • The designated delimiter character (tab by default), which is used to separate fields in the data file.
  • A UNIX-style line feed (\n or 0x0a), which is used to designate a new row in the data file. It is strongly recommended that applications generating COPY data convert data line feeds to UNIX-style line feeds rather than Microsoft Windows style carriage return line feeds (\r\n or 0x0a 0x0d).

If your data contains either of these characters, you must escape the character so COPY treats it as data and not as a field separator or new row.

By default, the escape character is a \ (backslash) for text-formatted files and a " (double quote) for csv-formatted files. If you want to use a different escape character, you can do so using the ESCAPE AS clause. Make sure to choose an escape character that is not used anywhere in your data file as an actual data value. You can also disable escaping in text-formatted files by using ESCAPE 'OFF'.

For example, suppose you have a table with three columns and you want to load the following three fields using COPY.

  • percentage sign = %
  • vertical bar = |
  • backslash = \

Your designated delimiter character is | (pipe character), and your designated escape character is * (asterisk). The formatted row in your data file would look like this:

percentage sign = % | vertical bar = *| | backslash = \

Notice how the pipe character that is part of the data has been escaped using the asterisk character (*). Also notice that we do not need to escape the backslash since we are using an alternative escape character.

The following characters must be preceded by the escape character if they appear as part of a column value: the escape character itself, newline, carriage return, and the current delimiter character. You can specify a different escape character using the ESCAPE AS clause.

CSV Format

This format is used for importing and exporting the Comma Separated Value (CSV) file format used by many other programs, such as spreadsheets. Instead of the escaping used by Greenplum Database standard text mode, it produces and recognizes the common CSV escaping mechanism.

The values in each record are separated by the DELIMITER character. If the value contains the delimiter character, the QUOTE character, the ESCAPE character (which is double quote by default), the NULL string, a carriage return, or line feed character, then the whole value is prefixed and suffixed by the QUOTE character. You can also use FORCE QUOTE to force quotes when outputting non-NULL values in specific columns.

The CSV format has no standard way to distinguish a NULL value from an empty string. Greenplum Database COPY handles this by quoting. A NULL is output as the NULL string and is not quoted, while a data value matching the NULL string is quoted. Therefore, using the default settings, a NULL is written as an unquoted empty string, while an empty string is written with double quotes (""). Reading values follows similar rules. You can use FORCE NOT NULL to prevent NULL input comparisons for specific columns.

Because backslash is not a special character in the CSV format, \., the end-of-data marker, could also appear as a data value. To avoid any misinterpretation, a \. data value appearing as a lone entry on a line is automatically quoted on output, and on input, if quoted, is not interpreted as the end-of-data marker. If you are loading a file created by another application that has a single unquoted column and might have a value of \., you might need to quote that value in the input file.

Note: In CSV mode, all characters are significant. A quoted value surrounded by white space, or any characters other than DELIMITER, will include those characters. This can cause errors if you import data from a system that pads CSV lines with white space out to some fixed width. If such a situation arises you might need to preprocess the CSV file to remove the trailing white space, before importing the data into Greenplum Database.
Note: CSV mode will both recognize and produce CSV files with quoted values containing embedded carriage returns and line feeds. Thus the files are not strictly one line per table row like text-mode files.
Note: Many programs produce strange and occasionally perverse CSV files, so the file format is more a convention than a standard. Thus you might encounter some files that cannot be imported using this mechanism, and COPY might produce files that other programs cannot process.

Examples

Copy a table to the client using the vertical bar (|) as the field delimiter:

COPY country TO STDOUT WITH DELIMITER '|';

Copy data from a file into the country table:

COPY country FROM '/home/usr1/sql/country_data';

Copy into a file just the countries whose names start with 'A':

COPY (SELECT * FROM country WHERE country_name LIKE 'A%') TO 
'/home/usr1/sql/a_list_countries.copy';

Create an error table called err_sales to use with single row error isolation mode:

CREATE TABLE err_sales ( cmdtime timestamptz, relname text, 
filename text, linenum int, bytenum int, errmsg text, rawdata text, rawbytes bytea ) DISTRIBUTED RANDOMLY;

Copy data from a file into the sales table using single row error isolation mode:

COPY sales FROM '/home/usr1/sql/sales_data' LOG ERRORS INTO 
err_sales SEGMENT REJECT LIMIT 10 ROWS;

Compatibility

There is no COPY statement in the SQL standard.