42.12. pg_class

Top  Previous  Next

42.12. pg_class

The catalog pg_class catalogs tables and most everything else that has columns or is otherwise similar to a table. This includes indexes (but see also pg_index), sequences, views, composite types, and some kinds of special relation; see relkind. Below, when we mean all of these kinds of objects we speak of “relations”. Not all columns are meaningful for all relation types.

Table 42.12. pg_class Columns

Name

Type

References

Description

relname

name


Name of the table, index, view, etc.

relnamespace

oid

pg_namespace.oid

The OID of the namespace that contains this relation

reltype

oid

pg_type.oid

The OID of the data type that corresponds to this table's row type, if any (zero for indexes, which have no pg_type entry)

relowner

oid

pg_authid.oid

Owner of the relation

relam

oid

pg_am.oid

If this is an index, the access method used (B-tree, hash, etc.)

relfilenode

oid


Name of the on-disk file of this relation; 0 if none

reltablespace

oid

pg_tablespace.oid

The tablespace in which this relation is stored. If zero, the database's default tablespace is implied. (Not meaningful if the relation has no on-disk file.)

relpages

int4


Size of the on-disk representation of this table in pages (of size BLCKSZ). This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.

reltuples

float4


Number of rows in the table. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.

reltoastrelid

oid

pg_class.oid

OID of the TOAST table associated with this table, 0 if none. The TOAST table stores large attributes “out of line” in a secondary table.

reltoastidxid

oid

pg_class.oid

For a TOAST table, the OID of its index. 0 if not a TOAST table.

relhasindex

bool


True if this is a table and it has (or recently had) any indexes. This is set by CREATE INDEX, but not cleared immediately by DROP INDEX. VACUUM clears relhasindex if it finds the table has no indexes.

relisshared

bool


True if this table is shared across all databases in the cluster. Only certain system catalogs (such as pg_database) are shared.

relkind

char


r = ordinary table, i = index, S = sequence, v = view, c = composite type, s = special, t = TOAST table

relnatts

int2


Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in pg_attribute. See also pg_attribute.attnum.

relchecks

int2


Number of check constraints on the table; see pg_constraint catalog

reltriggers

int2


Number of triggers on the table; see pg_trigger catalog

relukeys

int2


unused (not the number of unique keys)

relfkeys

int2


unused (not the number of foreign keys on the table)

relrefs

int2


unused

relhasoids

bool


True if we generate an OID for each row of the relation.

relhaspkey

bool


True if the table has (or once had) a primary key.

relhasrules

bool


True if table has rules; see pg_rewrite catalog.

relhassubclass

bool


True if table has (or once had) any inheritance children.

relacl

aclitem[]


Access privileges; see GRANT and REVOKE for details.