|Data type name
| The OID of the namespace that contains this type
|Owner (creator) 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, typlen is 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.
Only char, short, and
int equivalent items can be passed by value, so if
the type is not 1, 2, or 4 bytes long,
PostgreSQL does not have
the option of passing by value and so
typbyval had better be false.
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 is b for
a base type, c for a complex type (i.e.,
a table's row type), d for a derived type (i.e.,
a domain), or p for a pseudo-type. See also
|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 complex type (see
typtype), then this field 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-complex types.
| 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 oidvector.
If a fixed-length type has a typelem then
its internal representation must be N values of the
typelem data type with no other data.
Variable-length array types have a header defined by the array
|Input conversion function
|Output conversion 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
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, i.e., 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 by no means all).
Note: For types used in system tables, it is critical that the size
and alignment defined in pg_type
agree with the way that the compiler will lay out the field in
a struct 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 in "secondary".
Note that 'm' fields can also be moved out to secondary
storage, but only as a last resort ('e' and 'x' fields are
typnotnull represents a NOT NULL
constraint on a type. Presently used for domains only.
If this is a derived type (see typtype),
then typbasetype identifies
the type that this one is based on. Zero if not a derived type.
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 is the number of array dimensions
for a domain that is an array (that is, typbasetype is an array type;
the domain's typelem will match the base type's typelem).
Zero for non-domains and non-array domains.
If typdefaultbin is not NULL, it is the nodeToString
representation of a default expression for the type. Currently 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. 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.