PG_TYPE

PG_TYPE stores information about data types.

Table 1 PG_TYPE columns

Name	Type	Description
oid	oid	Row identifier (hidden attribute, which must be specified)
typname	name	Data type name
typnamespace	oid	OID of the namespace that contains the type
typowner	oid	Owner of the type
typlen	smallint	Number of bytes in the internal representation of the type for a fixed-size type. It is a negative number for a variable-length type. The value –1 indicates a "varlena" type (one that has a length word). The value –2 indicates a null-terminated C string.
typbyval	boolean	Specifies whether to pass a value (true) or a reference (false) when a value of this type is passed internally. typbyval is set to false if the value of typlen is not 1, 2, 4, or 8, because values of this type are always passed by reference of this column. typbyval can be false even if the typlen is passed by a parameter of this column.
typtype	"char"	b: base type. c: composite type (for example, a table's row type) d: domain p: pseudo For details, see 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.
typispreferred	boolean	The value is true if conversion is performed when data meets conversion rules specified by typcategory.
typisdefined	boolean	Whether a type has been defined. It is true if the type is defined, and false if this is a placeholder entry for a not-yet-defined type. When it 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 an 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 does not represent a table, but it is required for the type's PG_ATTRIBUTE entries to link to. It is 0 for non-composite type.
typelem	oid	If typelem is not 0, it identifies another row in PG_TYPE. The current type can be described as an array yielding values of type typelem. A "true" array type has a variable length (typlen = –1), but some fixed-length types (typlen > 0) also have non-zero typelem, for example name and point. If a fixed-length type has a typelem, its internal representation must be a 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 the value is not 0, the corresponding type record is available in PG_TYPE.
typinput	regproc	Input conversion function (text format)
typoutput	regproc	Output conversion function (text format)
typreceive	regproc	Input conversion function (binary format); 0 for non-input conversion function
typsend	regproc	output conversion function (binary format); 0 for non-output conversion function
typmodin	regproc	Type modifier input function; 0 if the type does not support modifiers
typmodout	regproc	Type modifier output function; 0 if the type does not support modifiers
typanalyze	regproc	Custom ANALYZE function; 0 if the standard function is used
typalign	"char"	Alignment required when storing a value of this type. It applies to storage on disks as well as most representations of the value inside openGauss. When multiple values are stored consecutively, such as in the representation of a complete row on disk, padding is inserted before a data 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, that is, no alignment needed s: short alignment (2 bytes on most machines) i: integer alignment (4 bytes on most machines) d: double alignment (8 bytes on many machines, but by no means all) NOTICE: For types used in system tables, the size and alignment defined in PG_TYPE must agree with the way that the compiler lays out the column in a structure representing a table row.
typstorage	"char"	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: Values are always stored plain. e: Values can be stored in a secondary relationship (if the relation has one, see pg_class.reltoastrelid). m: Values can be stored compressed inline. x: Values can be stored compressed inline or stored in secondary storage. NOTICE: m domains can also be moved out to secondary storage, but only as a last resort (e and x domains are moved first).
typenotnull	boolean	Whether the type has a NOTNULL constraint. Currently, it is used for domains only.
typbasetype	oid	If this is a domain (see typtype), then typbasetype identifies the type that this one is based on. The value is 0 if this type is not a derived type.
typtypmod	integer	Records the typtypmod to be applied to domains' base types by domains (the value is –1 if the base type does not use typmod). This is –1 if this type is not a domain.
typndims	integer	Number of array dimensions for a domain that is an array (typbasetype is an array type; the domain's typelem matches the base type's typelem). This is 0 for types other than domains over array types.
typcollation	oid	Sequence rule for specified types. For details about the value, see the system catalog in PG_COLLATION. (0 if sequencing is not supported)
typdefaultbin	pg_node_tree	nodeToString() representation of a default expression for the type if the value is non-null. Currently, this column is only used for domains.
typdefault	text	The value is NULL if a type has no associated default value. If typdefaultbin is not NULL, typdefault must contain a 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 can be fed to the type's input converter to produce a constant.
typacl	aclitem[]	Access permission