PostgreSQL 7.4 Documentation
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# 43.9. `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, 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 43-9. `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, if any (zero for indexes, which have no `pg_type` entry)
`relowner` | `int4` | `pg_shadow`.usesysid | 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
`relpages` | `int4` |  | Size of the on-disk representation of this table in pages (size `BLCKSZ`). This is only an estimate used by the planner. It is updated by `VACUUM`, `ANALYZE`, and `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 `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` |  | Table has rules; see `pg_rewrite` catalog
`relhassubclass` | `bool` |  | At least one table inherits from this one
`relacl` | `aclitem[]` |  | Access privileges; see the descriptions of `GRANT` and `REVOKE` for details.

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