begriffs open source - ai-pg/blob - full-docs/src/sgml/html/catalog-pg-class.html

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   3    The catalog <code class="structname">pg_class</code> describes tables and
   4    other objects that have columns or are otherwise similar to a
   5    table.  This includes indexes (but see also <a class="link" href="catalog-pg-index.html" title="52.26. pg_index"><code class="structname">pg_index</code></a>),
   6    sequences (but see also <a class="link" href="catalog-pg-sequence.html" title="52.47. pg_sequence"><code class="structname">pg_sequence</code></a>),
   7    views, materialized views, composite types, and TOAST tables;
   8    see <code class="structfield">relkind</code>.
   9    Below, when we mean all of these kinds of objects we speak of
  10    <span class="quote">“<span class="quote">relations</span>”</span>.  Not all of <code class="structname">pg_class</code>'s
  11    columns are meaningful for all relation kinds.
  12   </p><div class="table" id="id-1.10.4.13.4"><p class="title"><strong>Table 52.11. <code class="structname">pg_class</code> Columns</strong></p><div class="table-contents"><table class="table" summary="pg_class Columns" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
  13        Column Type
  14       </p>
  15       <p>
  16        Description
  17       </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
  18        <code class="structfield">oid</code> <code class="type">oid</code>
  19       </p>
  20       <p>
  21        Row identifier
  22       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  23        <code class="structfield">relname</code> <code class="type">name</code>
  24       </p>
  25       <p>
  26        Name of the table, index, view, etc.
  27       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  28        <code class="structfield">relnamespace</code> <code class="type">oid</code>
  29        (references <a class="link" href="catalog-pg-namespace.html" title="52.32. pg_namespace"><code class="structname">pg_namespace</code></a>.<code class="structfield">oid</code>)
  30       </p>
  31       <p>
  32        The OID of the namespace that contains this relation
  33       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  34        <code class="structfield">reltype</code> <code class="type">oid</code>
  35        (references <a class="link" href="catalog-pg-type.html" title="52.64. pg_type"><code class="structname">pg_type</code></a>.<code class="structfield">oid</code>)
  36       </p>
  37       <p>
  38        The OID of the data type that corresponds to this table's row type,
  39        if any; zero for indexes, sequences, and toast tables, which have
  40        no <code class="structname">pg_type</code> entry
  41       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  42        <code class="structfield">reloftype</code> <code class="type">oid</code>
  43        (references <a class="link" href="catalog-pg-type.html" title="52.64. pg_type"><code class="structname">pg_type</code></a>.<code class="structfield">oid</code>)
  44       </p>
  45       <p>
  46        For typed tables, the OID of the underlying composite type;
  47        zero for all other relations
  48       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  49        <code class="structfield">relowner</code> <code class="type">oid</code>
  50        (references <a class="link" href="catalog-pg-authid.html" title="52.8. pg_authid"><code class="structname">pg_authid</code></a>.<code class="structfield">oid</code>)
  51       </p>
  52       <p>
  53        Owner of the relation
  54       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  55        <code class="structfield">relam</code> <code class="type">oid</code>
  56        (references <a class="link" href="catalog-pg-am.html" title="52.3. pg_am"><code class="structname">pg_am</code></a>.<code class="structfield">oid</code>)
  57       </p>
  58       <p>
  59        The access method used to access this table or index.
  60        Not meaningful if the relation is a sequence or
  61        has no on-disk file,
  62        except for partitioned tables, where, if set, it takes
  63        precedence over <code class="varname">default_table_access_method</code>
  64        when determining the access method to use for partitions created
  65        when one is not specified in the creation command.
  66       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  67        <code class="structfield">relfilenode</code> <code class="type">oid</code>
  68       </p>
  69       <p>
  70        Name of the on-disk file of this relation; zero means this
  71        is a <span class="quote">“<span class="quote">mapped</span>”</span> relation whose disk file name is determined
  72        by low-level state
  73       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  74        <code class="structfield">reltablespace</code> <code class="type">oid</code>
  75        (references <a class="link" href="catalog-pg-tablespace.html" title="52.56. pg_tablespace"><code class="structname">pg_tablespace</code></a>.<code class="structfield">oid</code>)
  76       </p>
  77       <p>
  78        The tablespace in which this relation is stored.
  79        If zero, the database's default tablespace is implied.
  80        Not meaningful if the relation has no on-disk file,
  81        except for partitioned tables, where this is the tablespace
  82        in which partitions will be created when one is not
  83        specified in the creation command.
  84       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  85        <code class="structfield">relpages</code> <code class="type">int4</code>
  86       </p>
  87       <p>
  88        Size of the on-disk representation of this table in pages (of size
  89        <code class="symbol">BLCKSZ</code>).  This is only an estimate used by the
  90        planner.  It is updated by <a class="link" href="sql-vacuum.html" title="VACUUM"><code class="command">VACUUM</code></a>,
  91        <a class="link" href="sql-analyze.html" title="ANALYZE"><code class="command">ANALYZE</code></a>, and a few DDL commands such as
  92        <a class="link" href="sql-createindex.html" title="CREATE INDEX"><code class="command">CREATE INDEX</code></a>.
  93       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
  94        <code class="structfield">reltuples</code> <code class="type">float4</code>
  95       </p>
  96       <p>
  97        Number of live rows in the table.  This is only an estimate used by
  98        the planner.  It is updated by <a class="link" href="sql-vacuum.html" title="VACUUM"><code class="command">VACUUM</code></a>,
  99        <a class="link" href="sql-analyze.html" title="ANALYZE"><code class="command">ANALYZE</code></a>, and a few DDL commands such as
 100        <a class="link" href="sql-createindex.html" title="CREATE INDEX"><code class="command">CREATE INDEX</code></a>.
 101        If the table has never yet been vacuumed or
 102        analyzed, <code class="structfield">reltuples</code>
 103        contains <code class="literal">-1</code> indicating that the row count is
 104        unknown.
 105       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 106        <code class="structfield">relallvisible</code> <code class="type">int4</code>
 107       </p>
 108       <p>
 109        Number of pages that are marked all-visible in the table's
 110        visibility map.  This is only an estimate used by the
 111        planner.  It is updated by <a class="link" href="sql-vacuum.html" title="VACUUM"><code class="command">VACUUM</code></a>,
 112        <a class="link" href="sql-analyze.html" title="ANALYZE"><code class="command">ANALYZE</code></a>, and a few DDL commands such as
 113        <a class="link" href="sql-createindex.html" title="CREATE INDEX"><code class="command">CREATE INDEX</code></a>.
 114       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 115        <code class="structfield">relallfrozen</code> <code class="type">int4</code>
 116       </p>
 117       <p>
 118        Number of pages that are marked all-frozen in the table's visibility
 119        map.  This is only an estimate used for triggering autovacuums. It can
 120        also be used along with <code class="structfield">relallvisible</code> for
 121        scheduling manual vacuums and tuning <a class="link" href="runtime-config-vacuum.html#RUNTIME-CONFIG-VACUUM-FREEZING" title="19.10.4. Freezing">vacuum's freezing
 122        behavior</a>.
 123
 124        It is updated by
 125        <a class="link" href="sql-vacuum.html" title="VACUUM"><code class="command">VACUUM</code></a>,
 126        <a class="link" href="sql-analyze.html" title="ANALYZE"><code class="command">ANALYZE</code></a>,
 127        and a few DDL commands such as
 128        <a class="link" href="sql-createindex.html" title="CREATE INDEX"><code class="command">CREATE INDEX</code></a>.
 129       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 130        <code class="structfield">reltoastrelid</code> <code class="type">oid</code>
 131        (references <a class="link" href="catalog-pg-class.html" title="52.11. pg_class"><code class="structname">pg_class</code></a>.<code class="structfield">oid</code>)
 132       </p>
 133       <p>
 134        OID of the TOAST table associated with this table, zero if none.  The
 135        TOAST table stores large attributes <span class="quote">“<span class="quote">out of line</span>”</span> in a
 136        secondary table.
 137       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 138        <code class="structfield">relhasindex</code> <code class="type">bool</code>
 139       </p>
 140       <p>
 141        True if this is a table and it has (or recently had) any indexes
 142       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 143        <code class="structfield">relisshared</code> <code class="type">bool</code>
 144       </p>
 145       <p>
 146        True if this table is shared across all databases in the cluster.  Only
 147        certain system catalogs (such as <a class="link" href="catalog-pg-database.html" title="52.15. pg_database"><code class="structname">pg_database</code></a>)
 148        are shared.
 149       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 150        <code class="structfield">relpersistence</code> <code class="type">char</code>
 151       </p>
 152       <p>
 153        <code class="literal">p</code> = permanent table/sequence, <code class="literal">u</code> = unlogged table/sequence,
 154        <code class="literal">t</code> = temporary table/sequence
 155       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 156        <code class="structfield">relkind</code> <code class="type">char</code>
 157       </p>
 158       <p>
 159        <code class="literal">r</code> = ordinary table,
 160        <code class="literal">i</code> = index,
 161        <code class="literal">S</code> = sequence,
 162        <code class="literal">t</code> = TOAST table,
 163        <code class="literal">v</code> = view,
 164        <code class="literal">m</code> = materialized view,
 165        <code class="literal">c</code> = composite type,
 166        <code class="literal">f</code> = foreign table,
 167        <code class="literal">p</code> = partitioned table,
 168        <code class="literal">I</code> = partitioned index
 169       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 170        <code class="structfield">relnatts</code> <code class="type">int2</code>
 171       </p>
 172       <p>
 173        Number of user columns in the relation (system columns not
 174        counted).  There must be this many corresponding entries in
 175        <a class="link" href="catalog-pg-attribute.html" title="52.7. pg_attribute"><code class="structname">pg_attribute</code></a>.  See also
 176        <code class="structname">pg_attribute</code>.<code class="structfield">attnum</code>.
 177       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 178        <code class="structfield">relchecks</code> <code class="type">int2</code>
 179       </p>
 180       <p>
 181        Number of <code class="literal">CHECK</code> constraints on the table; see
 182        <a class="link" href="catalog-pg-constraint.html" title="52.13. pg_constraint"><code class="structname">pg_constraint</code></a> catalog
 183       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 184        <code class="structfield">relhasrules</code> <code class="type">bool</code>
 185       </p>
 186       <p>
 187        True if table has (or once had) rules; see
 188        <a class="link" href="catalog-pg-rewrite.html" title="52.45. pg_rewrite"><code class="structname">pg_rewrite</code></a> catalog
 189       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 190        <code class="structfield">relhastriggers</code> <code class="type">bool</code>
 191       </p>
 192       <p>
 193        True if table has (or once had) triggers; see
 194        <a class="link" href="catalog-pg-trigger.html" title="52.58. pg_trigger"><code class="structname">pg_trigger</code></a> catalog
 195       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 196        <code class="structfield">relhassubclass</code> <code class="type">bool</code>
 197       </p>
 198       <p>
 199        True if table or index has (or once had) any inheritance children or partitions
 200       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 201        <code class="structfield">relrowsecurity</code> <code class="type">bool</code>
 202       </p>
 203       <p>
 204        True if table has row-level security enabled; see
 205        <a class="link" href="catalog-pg-policy.html" title="52.38. pg_policy"><code class="structname">pg_policy</code></a> catalog
 206       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 207        <code class="structfield">relforcerowsecurity</code> <code class="type">bool</code>
 208       </p>
 209       <p>
 210        True if row-level security (when enabled) will also apply to table owner; see
 211        <a class="link" href="catalog-pg-policy.html" title="52.38. pg_policy"><code class="structname">pg_policy</code></a> catalog
 212       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 213        <code class="structfield">relispopulated</code> <code class="type">bool</code>
 214       </p>
 215       <p>
 216        True if relation is populated (this is true for all
 217        relations other than some materialized views)
 218       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 219        <code class="structfield">relreplident</code> <code class="type">char</code>
 220       </p>
 221       <p>
 222        Columns used to form <span class="quote">“<span class="quote">replica identity</span>”</span> for rows:
 223        <code class="literal">d</code> = default (primary key, if any),
 224        <code class="literal">n</code> = nothing,
 225        <code class="literal">f</code> = all columns,
 226        <code class="literal">i</code> = index with
 227        <code class="structfield">indisreplident</code> set (same as nothing if the
 228        index used has been dropped)
 229       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 230        <code class="structfield">relispartition</code> <code class="type">bool</code>
 231       </p>
 232       <p>
 233        True if table or index is a partition
 234       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 235        <code class="structfield">relrewrite</code> <code class="type">oid</code>
 236        (references <a class="link" href="catalog-pg-class.html" title="52.11. pg_class"><code class="structname">pg_class</code></a>.<code class="structfield">oid</code>)
 237       </p>
 238       <p>
 239        For new relations being written during a DDL operation that requires a
 240        table rewrite, this contains the OID of the original relation;
 241        otherwise zero.  That state is only visible internally; this field should
 242        never contain anything other than zero for a user-visible relation.
 243       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 244        <code class="structfield">relfrozenxid</code> <code class="type">xid</code>
 245       </p>
 246       <p>
 247        All transaction IDs before this one have been replaced with a permanent
 248        (<span class="quote">“<span class="quote">frozen</span>”</span>) transaction ID in this table.  This is used to track
 249        whether the table needs to be vacuumed in order to prevent transaction
 250        ID wraparound or to allow <code class="literal">pg_xact</code> to be shrunk.  Zero
 251        (<code class="symbol">InvalidTransactionId</code>) if the relation is not a table.
 252       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 253        <code class="structfield">relminmxid</code> <code class="type">xid</code>
 254       </p>
 255       <p>
 256        All multixact IDs before this one have been replaced by a
 257        transaction ID in this table.  This is used to track
 258        whether the table needs to be vacuumed in order to prevent multixact ID
 259        wraparound or to allow <code class="literal">pg_multixact</code> to be shrunk.  Zero
 260        (<code class="symbol">InvalidMultiXactId</code>) if the relation is not a table.
 261       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 262        <code class="structfield">relacl</code> <code class="type">aclitem[]</code>
 263       </p>
 264       <p>
 265        Access privileges; see <a class="xref" href="ddl-priv.html" title="5.8. Privileges">Section 5.8</a> for details
 266       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 267        <code class="structfield">reloptions</code> <code class="type">text[]</code>
 268       </p>
 269       <p>
 270        Access-method-specific options, as <span class="quote">“<span class="quote">keyword=value</span>”</span> strings
 271       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
 272        <code class="structfield">relpartbound</code> <code class="type">pg_node_tree</code>
 273       </p>
 274       <p>
 275        If table is a partition (see <code class="structfield">relispartition</code>),
 276        internal representation of the partition bound
 277       </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
 278    Several of the Boolean flags in <code class="structname">pg_class</code> are maintained
 279    lazily: they are guaranteed to be true if that's the correct state, but
 280    may not be reset to false immediately when the condition is no longer
 281    true.  For example, <code class="structfield">relhasindex</code> is set by
 282    <a class="link" href="sql-createindex.html" title="CREATE INDEX"><code class="command">CREATE INDEX</code></a>, but it is never cleared by
 283    <a class="link" href="sql-dropindex.html" title="DROP INDEX"><code class="command">DROP INDEX</code></a>.  Instead, <a class="link" href="sql-vacuum.html" title="VACUUM"><code class="command">VACUUM</code></a> clears
 284    <code class="structfield">relhasindex</code> if it finds the table has no indexes.  This
 285    arrangement avoids race conditions and improves concurrency.
 286   </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="catalog-pg-cast.html" title="52.10. pg_cast">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="catalogs.html" title="Chapter 52. System Catalogs">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="catalog-pg-collation.html" title="52.12. pg_collation">Next</a></td></tr><tr><td width="40%" align="left" valign="top">52.10. <code class="structname">pg_cast</code> </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 18.0 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 52.12. <code class="structname">pg_collation</code></td></tr></table></div></body></html>