pg_class
The catalog pg_class describes tables and other objects that have columns or are otherwise similar to a table. This includes indexes (but see also pg_index), sequences (but see also pg_sequence), views, materialized views, composite types, and TOAST tables; see relkind. Below, when we mean all of these kinds of objects we speak of “relations”. Not all of pg_class's columns are meaningful for all relation kinds.
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Definition PG 18
The catalog pg_class describes tables and other objects that have columns or are otherwise similar to a table. This includes indexes (but see also pg_index), sequences (but see also pg_sequence), views, materialized views, composite types, and TOAST tables; see relkind. Below, when we mean all of these kinds of objects we speak of “relations”. Not all of pg_class's columns are meaningful for all relation kinds.
Catalog columns
| Column | Type | Nullability | Description |
|---|---|---|---|
| oid | oid | Not null | Row identifier |
| relname | name | Not null | Name of the table, index, view, etc. |
| relnamespace | oid | Not null | The OID of the namespace that contains this relation |
| reltype | oid | Not null | The OID of the data type that corresponds to this table's row type, if any; zero for indexes, sequences, and toast tables, which have no pg_type entry |
| reloftype | oid | Not null | For typed tables, the OID of the underlying composite type; zero for all other relations |
| relowner | oid | Not null | Owner of the relation |
| relam | oid | Not null | The access method used to access this table or index. Not meaningful if the relation is a sequence or has no on-disk file, except for partitioned tables, where, if set, it takes precedence over default_table_access_method when determining the access method to use for partitions created when one is not specified in the creation command. |
| relfilenode | oid | Not null | Name of the on-disk file of this relation; zero means this is a “mapped” relation whose disk file name is determined by low-level state |
| reltablespace | oid | Not null | 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, except for partitioned tables, where this is the tablespace in which partitions will be created when one is not specified in the creation command. |
| relpages | int4 | Not null | 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 | Not null | Number of live 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. If the table has never yet been vacuumed or analyzed, reltuples contains -1 indicating that the row count is unknown. |
| relallvisible | int4 | Not null | Number of pages that are marked all-visible in the table's visibility map. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX. |
| relallfrozen | int4 | Not null | Number of pages that are marked all-frozen in the table's visibility map. This is only an estimate used for triggering autovacuums. It can also be used along with relallvisible for scheduling manual vacuums and tuning vacuum's freezing behavior. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX. |
| reltoastrelid | oid | Not null | OID of the TOAST table associated with this table, zero if none. The TOAST table stores large attributes “out of line” in a secondary table. |
| relhasindex | bool | Not null | True if this is a table and it has (or recently had) any indexes |
| relisshared | bool | Not null | True if this table is shared across all databases in the cluster. Only certain system catalogs (such as pg_database) are shared. |
| relpersistence | char | Not null | p = permanent table/sequence, u = unlogged table/sequence, t = temporary table/sequence |
| relkind | char | Not null | r = ordinary table, i = index, S = sequence, t = TOAST table, v = view, m = materialized view, c = composite type, f = foreign table, p = partitioned table, I = partitioned index |
| relnatts | int2 | Not null | 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 | Not null | Number of CHECK constraints on the table; see pg_constraint catalog |
| relhasrules | bool | Not null | True if table has (or once had) rules; see pg_rewrite catalog |
| relhastriggers | bool | Not null | True if table has (or once had) triggers; see pg_trigger catalog |
| relhassubclass | bool | Not null | True if table or index has (or once had) any inheritance children or partitions |
| relrowsecurity | bool | Not null | True if table has row-level security enabled; see pg_policy catalog |
| relforcerowsecurity | bool | Not null | True if row-level security (when enabled) will also apply to table owner; see pg_policy catalog |
| relispopulated | bool | Not null | True if relation is populated (this is true for all relations other than some materialized views) |
| relreplident | char | Not null | Columns used to form “replica identity” for rows: d = default (primary key, if any), n = nothing, f = all columns, i = index with indisreplident set (same as nothing if the index used has been dropped) |
| relispartition | bool | Not null | True if table or index is a partition |
| relrewrite | oid | Not null | For new relations being written during a DDL operation that requires a table rewrite, this contains the OID of the original relation; otherwise zero. That state is only visible internally; this field should never contain anything other than zero for a user-visible relation. |
| relfrozenxid | xid | Not null | 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_xact to be shrunk. Zero (InvalidTransactionId) if the relation is not a table. |
| relminmxid | xid | Not null | 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. Zero (InvalidMultiXactId) if the relation is not a table. |
| relacl | aclitem[] | Nullable | Access privileges; see Section 5.8 for details |
| reloptions | text[] | Nullable | Access-method-specific options, as “keyword=value” strings |
| relpartbound | pg_node_tree | Nullable | If table is a partition (see relispartition), internal representation of the partition bound |
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Complete source facts
runtime columns
oid, relname, relnamespace, reltype, reloftype, relowner, relam, relfilenode, reltablespace, relpages, reltuples, relallvisible, relallfrozen, reltoastrelid, relhasindex, relisshared, relpersistence, relkind, relnatts, relchecks, relhasrules, relhastriggers, relhassubclass, relrowsecurity, relforcerowsecurity, relispopulated, relreplident, relispartition, relrewrite, relfrozenxid, relminmxid, relacl, reloptions, relpartbound
Source references
Full definition and evidence JSON
Definition sources
center · PostgreSQL 18 · english-manuals:ea8872f33d2fe5c3e602b22cd56700b9d92f1a106fd1b4da3ff8e1290dd6b8cc
Text language: en · english-manuals:ea8872f33d2fe5c3e602b22cd56700b9d92f1a106fd1b4da3ff8e1290dd6b8cc