Row identifier (hidden attribute; must be explicitly selected)
Data type name
The OID of the namespace that contains this type
Owner of the type
For a fixed-size type,
typlen is the number of bytes in the internal representation of the type. But for a variable-length type,
typlenis negative. -1 indicates a “varlena” type (one that has a length word), -2 indicates a null-terminated C string.
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.
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
typcategory is an arbitrary classification of data types that is used by the parser to determine which implicit casts should be “preferred”. See Table 51.63.
True if the type is a preferred cast target within its
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.
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.
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 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
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 is not 0 then it identifies another row in
pg_type, which is the “true” array type having this type as element
Input conversion function (text format)
Output conversion function (text format)
Input conversion function (binary format), or 0 if none
Output conversion function (binary format), or 0 if none
Type modifier input function, or 0 if type does not support modifiers
Type modifier output function, or 0 to use the standard format
ANALYZE function, or 0 to use the standard function
typalign is 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 PostgreSQL. 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:
char alignment, i.e., no alignment needed.
short alignment (2 bytes on most machines).
int alignment (4 bytes on most machines).
double alignment (8 bytes on many machines, but by no means all).NoteFor types used in system tables, it is critical that the size and alignment defined in
pg_typeagree with the way that the compiler will lay out the column in a structure representing a table row.
typstorage tells for varlena types (those with
typlen = -1) 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
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 (
x columns are moved first).
typnotnull represents a not-null constraint on a type. Used for domains only.
If this is a domain (see
typbasetype identifies the type that this one is based on. Zero if this type is not a domain.
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 is the number of array dimensions for a domain over an array (that is,
typbasetype is an array type). Zero for types other than domains over array types.
typcollation specifies the collation of the type. If the type does not support collations, this will be zero. A base type that supports collations will have
DEFAULT_COLLATION_OID here. A domain over a collatable type can have some other collation OID, if one was specified for the domain.
typdefaultbin is not null, it is the
nodeToString() representation of a default expression for the type. This is only used for domains.
typdefault is null if the type has no associated default value. If
typdefaultbin is not null,
typdefault must contain a human-readable version of the default expression represented by
typdefaultbin is null and
typdefault is not, then
typdefault is the external representation of the type's default value, which can be fed to the type's input converter to produce a constant.
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