The catalog pg_type
stores information about data types. Base types and enum 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
.
Table 50-55. pg_type
Columns
Name | Type | References | Description |
---|---|---|---|
oid | oid | Row identifier (hidden attribute; must be explicitly selected) | |
typname | name | Data type name | |
typnamespace | oid |
| The OID of the namespace that contains this type |
typowner | 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 | bool |
typbyval 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. | |
typtype | char |
typtype is b for a base type, c for a composite type (e.g., a table's row type), d for a domain, e for an enum type, p for a pseudo-type, or r for a range type. See also typrelid and typbasetype . | |
typcategory | char |
typcategory is an arbitrary classification of data types that is used by the parser to determine which implicit casts should be "preferred". See Table 50-56. | |
typispreferred | bool | True if the type is a preferred cast target within its typcategory
| |
typisdefined | bool | True if the type is defined, false if this is a placeholder entry for a not-yet-defined type. When typisdefined is 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 |
| If this is a composite type (see typtype ), then this column points to the pg_class entry that defines the corresponding table. (For a free-standing composite type, the pg_class entry doesn't 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 |
| If typelem is 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 (typlen > 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. |
typarray | oid |
| If typarray is not 0 then it identifies another row in pg_type , which is the "true" array type having this type as element |
typinput | regproc |
| Input conversion function (text format) |
typoutput | regproc |
| Output conversion function (text format) |
typreceive | regproc |
| Input conversion function (binary format), or 0 if none |
typsend | regproc |
| Output conversion function (binary format), or 0 if none |
typmodin | regproc |
| Type modifier input function, or 0 if type does not support modifiers |
typmodout | regproc |
| Type modifier output function, or 0 to use the standard format |
typanalyze | regproc |
| Custom ANALYZE function, or 0 to use the standard function |
typalign | char |
Possible values are:
| |
typstorage | char |
Note that | |
typnotnull | bool |
| |
typbasetype | oid |
| If this is a domain (see |
typtypmod | int4 | Domains use | |
typndims | int4 |
| |
typcollation | oid |
|
|
typdefaultbin | pg_node_tree | If | |
typdefault | text |
| |
typacl | aclitem[] | Access privileges; see GRANT and REVOKE for details |
Table 50-56 lists the system-defined values of typcategory
. Any future additions to this list will also be upper-case ASCII letters. All other ASCII characters are reserved for user-defined categories.
Table 50-56. typcategory
Codes
Code | Category |
---|---|
A | Array types |
B | Boolean types |
C | Composite types |
D | Date/time types |
E | Enum types |
G | Geometric types |
I | Network address types |
N | Numeric types |
P | Pseudo-types |
R | Range types |
S | String types |
T | Timespan types |
U | User-defined types |
V | Bit-string types |
X |
unknown type |
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