The catalog pg_type
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
.
Table 43.34. pg_type
Columns
Name | Type | References | Description |
---|---|---|---|
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; this is currently true for
type float4 , for example
|
|
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, or
p for a pseudo-type. See also
typrelid and
typbasetype
|
|
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
|
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 |
typanalyze |
regproc |
|
Custom ANALYZE function, or 0 to use the standard function |
typalign |
char |
Possible values are:
Note For types used in system tables, it is critical that the size
and alignment defined in |
|
typstorage |
char |
Note that |
|
typnotnull |
bool |
|
|
typbasetype |
oid |
|
If this is a domain (see |
typtypmod |
int4 |
Domains use |
|
typndims |
int4 |
|
|
typdefaultbin |
text |
If |
|
typdefault |
text |
|