pg_class

The system catalog table pg_class catalogs tables and most everything else that has columns or is otherwise similar to a table (also known as relations). This includes indexes (see also pg_index), sequences, views, composite types, and TOAST tables. Not all columns are meaningful for all relation types.

Column Type References Description

Column	Type	References	Description
relname	name	—	Name of the table, index, view, and so on
relnamespace	oid	pg_namespace.oid	The OID of the namespace (schema) 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 (`0` for indexes, which have no `pg_type` entry)
reloftype	oid	pg_type.oid	The OID of an entry in pg_type for an underlying composite type
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, Bitmap, GIN, and so on)
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 `0`, the database’s default tablespace is implied. Not meaningful if the relation has no on-disk file
relpages	integer	—	Size of the on-disk representation of this table in pages. This is only an estimate used by the planner. It is updated by `VACUUM`, `ANALYZE`, and a few DDL commands
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
relallvisible	int32	—	Number of all-visible blocks (this value may not be up to date)
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
relhasindex	boolean	—	`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` will clear if it finds the table has no indexes
relisshared	boolean	—	`true` if this table is shared across all databases in the system. Only certain system catalog tables are shared
relpersistence	char	—	The type of object persistence: `p` — heap or append-optimized table. `u` — unlogged table. `t` — temporary table.
relkind	char	—	The type of object: `r` — heap or append-optimized table. `i` — index. `S` — sequence. `t` — TOAST value. `v` — view. `m` — materialized view. `c` — composite type. `f` — foreign table. `u` — uncatalogued temporary heap table. `o` — internal append-optimized segment files and EOFs. `b` — append-only block directory. `M` — append-only visibility map.
relstorage	char	—	The storage mode of a table: `a` — append-optimized. `c` — column-oriented. `h` — heap. `v` — virtual. `x` — external table. `f` — foreign table.
relnatts	int2	—	Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in `pg_attribute`
relchecks	int2	—	Number of check constraints on the table
relhasoids	boolean	—	`true` if an OID is generated for each row of the relation
relhaspkey	boolean	—	`true` if the table has (or once had) a primary key
relhasrules	boolean	—	`true` if table has rules
relhastriggers	boolean	—	`true` if table has (or once had) triggers
relhassubclass	boolean	—	`true` if table has (or once had) any inheritance children
relispopulated	boolean	—	`true` if relation is populated (this is true for all relations other than some materialized views)
relreplident	char	—	Columns used to form "replica identity" for rows: `d` — default (primary key, if any). `n` — nothing. `f` — all columns. `i` — index with `indisreplident` set, or default.
relfrozenxid	xid	—	All transaction IDs before this one have been replaced with a permanent (frozen) transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent transaction ID wraparound or to allow `pg_clog` to be shrunk. The value is `0` (`InvalidTransactionId`) if the relation is not a table or if the table does not require vacuuming to prevent transaction ID wraparound. The table still might require vacuuming to reclaim disk space
relminmxid	xid	—	All multixact IDs before this one have been replaced by a transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent multixact ID wraparound or to allow `pg_multixact` to be shrunk. `0` (`InvalidMultiXactId`) if the relation is not a table
relacl	aclitem[]	—	Access privileges assigned by `GRANT` and `REVOKE`
reloptions	text[]	—	Access-method-specific options, as `keyword=value` strings

relname

name

—

Name of the table, index, view, and so on

relnamespace

oid

pg_namespace.oid

The OID of the namespace (schema) 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 (0 for indexes, which have no pg_type entry)

reloftype

oid

pg_type.oid

The OID of an entry in pg_type for an underlying composite type

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, Bitmap, GIN, and so on)

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 0, the database’s default tablespace is implied. Not meaningful if the relation has no on-disk file

relpages

integer

—

Size of the on-disk representation of this table in pages. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands

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

relallvisible

int32

—

Number of all-visible blocks (this value may not be up to date)

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

relhasindex

boolean

—

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 will clear if it finds the table has no indexes

relisshared

boolean

—

true if this table is shared across all databases in the system. Only certain system catalog tables are shared

relpersistence

char

—

The type of object persistence:

p — heap or append-optimized table.
u — unlogged table.
t — temporary table.

relkind

char

—

The type of object:

r — heap or append-optimized table.
i — index.
S — sequence.
t — TOAST value.
v — view.
m — materialized view.
c — composite type.
f — foreign table.
u — uncatalogued temporary heap table.
o — internal append-optimized segment files and EOFs.
b — append-only block directory.
M — append-only visibility map.

relstorage

char

—

The storage mode of a table:

a — append-optimized.
c — column-oriented.
h — heap.
v — virtual.
x — external table.
f — foreign table.

relnatts

int2

—

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

relchecks

int2

—

Number of check constraints on the table

relhasoids

boolean

—

true if an OID is generated for each row of the relation

relhaspkey

boolean

—

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

relhasrules

boolean

—

true if table has rules

relhastriggers

boolean

—

true if table has (or once had) triggers

relhassubclass

boolean

—

true if table has (or once had) any inheritance children

relispopulated

boolean

—

true if relation is populated (this is true for all relations other than some materialized views)

relreplident

char

—

Columns used to form "replica identity" for rows:

d — default (primary key, if any).
n — nothing.
f — all columns.
i — index with indisreplident set, or default.

relfrozenxid

xid

—

All transaction IDs before this one have been replaced with a permanent (frozen) transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_clog to be shrunk.

The value is 0 (InvalidTransactionId) if the relation is not a table or if the table does not require vacuuming to prevent transaction ID wraparound. The table still might require vacuuming to reclaim disk space

relminmxid

xid

—

All multixact IDs before this one have been replaced by a transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent multixact ID wraparound or to allow pg_multixact to be shrunk. 0 (InvalidMultiXactId) if the relation is not a table

relacl

aclitem[]

—

Access privileges assigned by GRANT and REVOKE

reloptions

text[]

—

Access-method-specific options, as keyword=value strings

pg_cast

pg_compression