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The pg_type system catalog table stores information about data types. Base types (scalar types) are created with CREATE TYPE, and domains with CREATE DOMAIN. A composite type is automatically created for each table in the database, to represent the row structure of the table. It is also possible to create composite types with CREATE TYPE AS.
|typname||name||Data type name.|
|typnamespace||oid||pg_namespace.oid||The OID of the namespace that contains this type.|
|typowner||oid||pg_authid.oid||Owner of the type.|
|typlen||int2||For a fixed-size type, typlen is the number of bytes in the internal representation of the type. But for a variable-length type, typlen is negative. -1 indicates a 'varlena' type (one that has a length word), -2 indicates a null-terminated C string.|
|typbyval||boolean||Determines whether internal routines pass a value of this type by value or by reference. typbyval had better be false if typlen is not 1, 2, or 4 (or 8 on machines where Datum is 8 bytes). Variable-length types are always passed by reference. Note that typbyval can be false even if the length would allow pass-by-value; this is currently true for type float4, for example.|
|typtype||char||b for a base type, c for a composite type, d for a domain, or p for a pseudo-type.|
|typisdefined||boolean||True if the type is defined, false if this is a placeholder entry for a not-yet-defined type. When false, nothing except the type name, namespace, and OID can be relied on.|
|typdelim||char||Character that separates two values of this type when parsing array input. Note that the delimiter is associated with the array element data type, not the array data type.|
|typrelid||oid||pg_class.oid||If this is a composite type, then this column points to the pg_class entry that defines the corresponding table. (For a free-standing composite type, the pg_class entry does not really represent a table, but it is needed anyway for the type's pg_attribute entries to link to.) Zero for non-composite types.|
|typelem||oid||pg_type.oid||If not 0 then it identifies another row in pg_type. The current type can then be subscripted like an array yielding values of type typelem. A true array type is variable length (typlen = -1), but some fixed-length (tylpen > 0) types also have nonzero typelem, for example name and point. If a fixed-length type has a typelem then its internal representation must be some number of values of the typelem data type with no other data. Variable-length array types have a header defined by the array subroutines.|
|typinput||regproc||pg_proc.oid||Input conversion function (text format).|
|typoutput||regproc||pg_proc.oid||Output conversion function (text format).|
|typreceive||regproc||pg_proc.oid||Input conversion function (binary format), or 0 if none.|
|typsend||regproc||pg_proc.oid||Output conversion function (binary format), or 0 if none.|
|typanalyze||regproc||pg_proc.oid||Custom ANALYZE function, or 0 to use the standard function.|
|typalign||char||The alignment required when storing a value of this type. It
applies to storage on disk as well as most representations of the value inside
Greenplum Database. When multiple values are stored consecutively,
such as in the representation of a complete row on disk, padding is inserted before a
datum of this type so that it begins on the specified boundary. The alignment
reference is the beginning of the first datum in the sequence. Possible values are:
c = char alignment (no alignment needed).
s = short alignment (2 bytes on most machines).
i = int alignment (4 bytes on most machines).
d = double alignment (8 bytes on many machines, but not all).
|typstorage||char||For varlena types (those with typlen = -1) tells
if the type is prepared for toasting and what the default strategy for attributes of
this type should be. Possible values are:
p: Value must always be stored plain.
e: Value can be stored in a secondary relation (if relation has one, see pg_class.reltoastrelid).
m: Value can be stored compressed inline.
x: Value can be stored compressed inline or stored in secondary storage.
Note that m columns can also be moved out to secondary storage, but only as a last resort (e and x columns are moved first).
|typnotnull||boolean||Represents a not-null constraint on a type. Used for domains only.|
|typbasetype||oid||pg_type.oid||Identifies the type that a domain is based on. Zero if this type is not a domain.|
|typtypmod||int4||Domains use typtypmod to record the typmod to be applied to their base type (-1 if base type does not use a typmod). -1 if this type is not a domain.|
|typndims||int4||The number of array dimensions for a domain that is an array (if typbasetype is an array type; the domain's typelem will match the base type's typelem). Zero for types other than array domains.|
|typdefaultbin||text||If not null, it is the nodeToString() representation of a default expression for the type. This is only used for domains.|
|typdefault||text||Null if the type has no associated default value. If not null, typdefault must contain a human-readable version of the default expression represented by typdefaultbin. If typdefaultbin is null and typdefault is not, then typdefault is the external representation of the type's default value, which may be fed to the type's input converter to produce a constant.|