markdown/reference/catalog/pg_class.html.md.erb

---
title: pg_class
---

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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](pg_index.html#topic1)), sequences, views, composite types, and TOAST tables. Not all columns are meaningful for all relation types.

<a id="topic1__gf143898"></a>
<span class="tablecap">Table 1. pg\_catalog.pg\_class</span>

<table>
<colgroup>
<col width="25%" />
<col width="25%" />
<col width="25%" />
<col width="25%" />
</colgroup>
<thead>
<tr class="header">
<th>column</th>
<th>type</th>
<th>references</th>
<th>description</th>
</tr>
</thead>
<tbody>
<tr class="odd">
<td><code class="ph codeph">relname</code></td>
<td>name</td>
<td> </td>
<td>Name of the table, index, view, etc.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relnamespace</code></td>
<td>oid</td>
<td>pg_namespace.oid</td>
<td>The OID of the namespace (schema) that contains this relation</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">reltype</code></td>
<td>oid</td>
<td>pg_type.oid</td>
<td>The OID of the data type that corresponds to this table's row type, if any (zero for indexes, which have no <code class="ph codeph">pg_type</code> entry)</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relowner</code></td>
<td>oid</td>
<td>pg_authid.oid</td>
<td>Owner of the relation</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relam</code></td>
<td>oid</td>
<td>pg_am.oid</td>
<td>If this is an index, the access method used (B-tree, Bitmap, hash, etc.)</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relfilenode</code></td>
<td>oid</td>
<td> </td>
<td>Name of the on-disk file of this relation; <code class="ph codeph">0</code> if none.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">reltablespace</code></td>
<td>oid</td>
<td>pg_tablespace.oid</td>
<td>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.)</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relpages</code></td>
<td>integer</td>
<td> </td>
<td>Size of the on-disk representation of this table in pages (of 32K each). This is only an estimate used by the planner. It is updated by  <code class="ph codeph">ANALYZE</code>, and a few DDL commands.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">reltuples</code></td>
<td>real</td>
<td> </td>
<td>Number of rows in the table. This is only an estimate used by the planner. It is updated by <code class="ph codeph">VACUUM</code>, <code class="ph codeph">ANALYZE</code>, and a few DDL commands.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">reltoastrelid</code></td>
<td>oid</td>
<td>pg_class.oid</td>
<td>OID of the TOAST table associated with this table, <code class="ph codeph">0</code> if none. The TOAST table stores large attributes &quot;out of line&quot; in a secondary table.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">reltoastidxid</code></td>
<td>oid</td>
<td>pg_class.oid</td>
<td>For a TOAST table, the OID of its index. <code class="ph codeph">0</code> if not a TOAST table.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relaosegidxid</code></td>
<td>oid</td>
<td> </td>
<td>Deprecated.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relaosegrelid</code></td>
<td>oid</td>
<td> </td>
<td>Deprecated.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relhasindex </code></td>
<td>boolean</td>
<td> </td>
<td>True if this is a table and it has (or recently had) any indexes. This is set by <code class="ph codeph">CREATE INDEX</code>, but not cleared immediately by <code class="ph codeph">DROP INDEX</code>. <code class="ph codeph">VACUUM</code> will clear if it finds the table has no indexes.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relisshared</code></td>
<td>boolean</td>
<td> </td>
<td>True if this table is shared across all databases in the system. Only certain system catalog tables are shared.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relkind</code></td>
<td>char</td>
<td> </td>
<td>The type of object
<p><code class="ph codeph">r</code> = heap table, <code class="ph codeph">i</code> = index, <code class="ph codeph">S</code> = sequence, <code class="ph codeph">v</code> = view, <code class="ph codeph">c</code> = composite type, <code class="ph codeph">t</code> = TOAST value, <code class="ph codeph">c</code> = composite type, <code class="ph codeph">u</code> = uncataloged temporary heap table</p></td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relstorage</code></td>
<td>char</td>
<td> </td>
<td>The storage mode of a table
<p><code class="ph codeph">a</code> = append-only, <code class="ph codeph">h</code> = heap, <code class="ph codeph">p</code> = append-only parquet, <code class="ph codeph">v</code> = virtual, <code class="ph codeph">x</code>= external table.</p></td>
</tr>
<tr class="even">
<td><code class="ph codeph">relnatts</code></td>
<td>smallint</td>
<td> </td>
<td>Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in pg_attribute.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relchecks</code></td>
<td>smallint</td>
<td> </td>
<td>Number of check constraints on the table.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">reltriggers</code></td>
<td>smallint</td>
<td> </td>
<td>Number of triggers on the table.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relukeys</code></td>
<td>smallint</td>
<td> </td>
<td>Unused</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relfkeys</code></td>
<td>smallint</td>
<td> </td>
<td>Unused</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relrefs</code></td>
<td>smallint</td>
<td> </td>
<td>Unused</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relhasoids</code></td>
<td>boolean</td>
<td> </td>
<td>True if an OID is generated for each row of the relation.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relhaspkey</code></td>
<td>boolean</td>
<td> </td>
<td>True if the table once had a primary key.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relhasrules</code></td>
<td>boolean</td>
<td> </td>
<td>True if table has rules.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relhassubclass</code></td>
<td>boolean</td>
<td> </td>
<td>True if table has (or once had) any inheritance children.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">relfrozenxid</code></td>
<td>xid</td>
<td> </td>
<td>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. Zero (<code class="ph codeph">InvalidTransactionId</code>) if the relation is not a table.</td>
</tr>
<tr class="odd">
<td><code class="ph codeph">relacl</code></td>
<td>aclitem[]</td>
<td> </td>
<td>Access privileges assigned by <code class="ph codeph">GRANT</code> and <code class="ph codeph">REVOKE</code>.</td>
</tr>
<tr class="even">
<td><code class="ph codeph">reloptions</code></td>
<td>text[]</td>
<td> </td>
<td>Access-method-specific options, as &quot;keyword=value&quot; strings.</td>
</tr>
</tbody>
</table>