PostgreSQL 7.1.3 Documentation
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# 3.5. pg_class

`pg_class` catalogues tables and mostly everything else that has columns or is otherwise similar to a table. This includes indexes (but see `pg_index`), sequences, views, and some kinds of special relation kinds. Below, when we mean all of these kinds of objects we speak of "relations". Not all fields are meaningful for all relation types.

Table 3-5. pg_class Columns

Name | Type | References | Description
--- | --- | --- | ---
relname | `name` |  | Name of the table, index, view, etc.
reltype | `oid` | pg_type.oid | The data type that corresponds to this table (not functional, only set for system tables)
relowner | `int4` | pg_shadow.usesysid | Owner of the relation
relam | `oid` | pg_am.oid | If this is an index, the access method used (btree, hash, etc.)
relfilenode | `oid` |  | Name of the on-disk file of this relation
relpages | `int4` |  | Size of the on-disk representation of this table in pages (size BLCKSZ). This is only an approximate value which is calculated during vacuum.
reltuples | `int4` |  | Number of tuples in the table. This is only an estimate used by the planner, updated by VACUUM.
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 | Oid of the index on the TOAST table for this table, 0 if none
relhasindex | `bool` |  | True if this is a table and it has at least one index
relisshared | `bool` |  | XXX (This is not what it seems to be.)
relkind | `char` |  | 'r' = ordinary table, 'i' = index, 'S' = sequence, 'v' = view, 's' = special, 't' = secondary TOAST table
relnatts | `int2` |  | Number of columns in the relation, besides system columns. 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_relcheck` catalog
reltriggers | `int2` |  | Number of triggers on the table; see `pg_trigger` catalog
relukeys | `int2` |  | unused (Not the number of unique keys or something.)
relfkeys | `int2` |  | Number foreign keys on the table
relhaspkey | `bool` |  | unused (No, this does not say whether the table has a primary key. It's really unused.)
relhasrules | `bool` |  | Table has rules
relhassubclass | `bool` |  | At least one table inherits this one
relacl | `aclitem[]` |  | Access permissions. See the descriptions of GRANT and REVOKE for details.

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