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><H1
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><A
NAME="CATALOG-PG-CLASS"
>45.11. <TT
CLASS="STRUCTNAME"
>pg_class</TT
></A
></H1
><P
> The catalog <TT
CLASS="STRUCTNAME"
>pg_class</TT
> catalogs tables and most
everything else that has columns or is otherwise similar to a
table. This includes indexes (but see also
<TT
CLASS="STRUCTNAME"
>pg_index</TT
>), sequences, views, composite types,
and TOAST tables; see <TT
CLASS="STRUCTFIELD"
>relkind</TT
>.
Below, when we mean all of these
kinds of objects we speak of <SPAN
CLASS="QUOTE"
>"relations"</SPAN
>. Not all
columns are meaningful for all relation types.
</P
><DIV
CLASS="TABLE"
><A
NAME="AEN89630"
></A
><P
><B
>Table 45-11. <TT
CLASS="STRUCTNAME"
>pg_class</TT
> Columns</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><THEAD
><TR
><TH
>Name</TH
><TH
>Type</TH
><TH
>References</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relname</TT
></TD
><TD
><TT
CLASS="TYPE"
>name</TT
></TD
><TD
> </TD
><TD
>Name of the table, index, view, etc.</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relnamespace</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-namespace.html"
><TT
CLASS="STRUCTNAME"
>pg_namespace</TT
></A
>.oid</TT
></TD
><TD
> The OID of the namespace that contains this relation
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>reltype</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-type.html"
><TT
CLASS="STRUCTNAME"
>pg_type</TT
></A
>.oid</TT
></TD
><TD
> The OID of the data type that corresponds to this table's row type,
if any (zero for indexes, which have no <TT
CLASS="STRUCTNAME"
>pg_type</TT
> entry)
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>reloftype</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-type.html"
><TT
CLASS="STRUCTNAME"
>pg_type</TT
></A
>.oid</TT
></TD
><TD
> For typed tables, the OID of the underlying composite type,
zero for all other relations
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relowner</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-authid.html"
><TT
CLASS="STRUCTNAME"
>pg_authid</TT
></A
>.oid</TT
></TD
><TD
>Owner of the relation</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relam</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-am.html"
><TT
CLASS="STRUCTNAME"
>pg_am</TT
></A
>.oid</TT
></TD
><TD
>If this is an index, the access method used (B-tree, hash, etc.)</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relfilenode</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
> </TD
><TD
>Name of the on-disk file of this relation; zero means this
is a <SPAN
CLASS="QUOTE"
>"mapped"</SPAN
> relation whose disk file name is determined
by low-level state</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>reltablespace</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-tablespace.html"
><TT
CLASS="STRUCTNAME"
>pg_tablespace</TT
></A
>.oid</TT
></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
><TD
><TT
CLASS="STRUCTFIELD"
>relpages</TT
></TD
><TD
><TT
CLASS="TYPE"
>int4</TT
></TD
><TD
> </TD
><TD
> Size of the on-disk representation of this table in pages (of size
<TT
CLASS="SYMBOL"
>BLCKSZ</TT
>). This is only an estimate used by the
planner. It is updated by <TT
CLASS="COMMAND"
>VACUUM</TT
>,
<TT
CLASS="COMMAND"
>ANALYZE</TT
>, and a few DDL commands such as
<TT
CLASS="COMMAND"
>CREATE INDEX</TT
>.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>reltuples</TT
></TD
><TD
><TT
CLASS="TYPE"
>float4</TT
></TD
><TD
> </TD
><TD
> Number of rows in the table. This is only an estimate used by the
planner. It is updated by <TT
CLASS="COMMAND"
>VACUUM</TT
>,
<TT
CLASS="COMMAND"
>ANALYZE</TT
>, and a few DDL commands such as
<TT
CLASS="COMMAND"
>CREATE INDEX</TT
>.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relallvisible</TT
></TD
><TD
><TT
CLASS="TYPE"
>int4</TT
></TD
><TD
> </TD
><TD
> 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 <TT
CLASS="COMMAND"
>VACUUM</TT
>,
<TT
CLASS="COMMAND"
>ANALYZE</TT
>, and a few DDL commands such as
<TT
CLASS="COMMAND"
>CREATE INDEX</TT
>.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>reltoastrelid</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-class.html"
><TT
CLASS="STRUCTNAME"
>pg_class</TT
></A
>.oid</TT
></TD
><TD
> OID of the TOAST table associated with this table, 0 if none. The
TOAST table stores large attributes <SPAN
CLASS="QUOTE"
>"out of line"</SPAN
> in a
secondary table.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>reltoastidxid</TT
></TD
><TD
><TT
CLASS="TYPE"
>oid</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-class.html"
><TT
CLASS="STRUCTNAME"
>pg_class</TT
></A
>.oid</TT
></TD
><TD
> For a TOAST table, the OID of its index. 0 if not a TOAST table.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relhasindex</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
> </TD
><TD
> True if this is a table and it has (or recently had) any indexes
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relisshared</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
> </TD
><TD
> True if this table is shared across all databases in the cluster. Only
certain system catalogs (such as <TT
CLASS="STRUCTNAME"
>pg_database</TT
>)
are shared.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relpersistence</TT
></TD
><TD
><TT
CLASS="TYPE"
>char</TT
></TD
><TD
> </TD
><TD
> <TT
CLASS="LITERAL"
>p</TT
> = permanent table, <TT
CLASS="LITERAL"
>u</TT
> = unlogged table,
<TT
CLASS="LITERAL"
>t</TT
> = temporary table
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relkind</TT
></TD
><TD
><TT
CLASS="TYPE"
>char</TT
></TD
><TD
> </TD
><TD
> <TT
CLASS="LITERAL"
>r</TT
> = ordinary table, <TT
CLASS="LITERAL"
>i</TT
> = index,
<TT
CLASS="LITERAL"
>S</TT
> = sequence, <TT
CLASS="LITERAL"
>v</TT
> = view, <TT
CLASS="LITERAL"
>c</TT
> =
composite type, <TT
CLASS="LITERAL"
>t</TT
> = TOAST table,
<TT
CLASS="LITERAL"
>f</TT
> = foreign table
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relnatts</TT
></TD
><TD
><TT
CLASS="TYPE"
>int2</TT
></TD
><TD
> </TD
><TD
> Number of user columns in the relation (system columns not
counted). There must be this many corresponding entries in
<TT
CLASS="STRUCTNAME"
>pg_attribute</TT
>. See also
<TT
CLASS="LITERAL"
>pg_attribute.attnum</TT
>.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relchecks</TT
></TD
><TD
><TT
CLASS="TYPE"
>int2</TT
></TD
><TD
> </TD
><TD
> Number of <TT
CLASS="LITERAL"
>CHECK</TT
> constraints on the table; see
<A
HREF="catalog-pg-constraint.html"
><TT
CLASS="STRUCTNAME"
>pg_constraint</TT
></A
> catalog
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relhasoids</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
> </TD
><TD
> True if we generate an OID for each row of the relation
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relhaspkey</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
> </TD
><TD
> True if the table has (or once had) a primary key
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relhasrules</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
> </TD
><TD
> True if table has (or once had) rules; see
<A
HREF="catalog-pg-rewrite.html"
><TT
CLASS="STRUCTNAME"
>pg_rewrite</TT
></A
> catalog
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relhastriggers</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
> </TD
><TD
> True if table has (or once had) triggers; see
<A
HREF="catalog-pg-trigger.html"
><TT
CLASS="STRUCTNAME"
>pg_trigger</TT
></A
> catalog
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relhassubclass</TT
></TD
><TD
><TT
CLASS="TYPE"
>bool</TT
></TD
><TD
> </TD
><TD
>True if table has (or once had) any inheritance children</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relfrozenxid</TT
></TD
><TD
><TT
CLASS="TYPE"
>xid</TT
></TD
><TD
> </TD
><TD
> All transaction IDs before this one have been replaced with a permanent
(<SPAN
CLASS="QUOTE"
>"frozen"</SPAN
>) 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 <TT
CLASS="LITERAL"
>pg_clog</TT
> to be shrunk. Zero
(<TT
CLASS="SYMBOL"
>InvalidTransactionId</TT
>) if the relation is not a table.
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>relacl</TT
></TD
><TD
><TT
CLASS="TYPE"
>aclitem[]</TT
></TD
><TD
> </TD
><TD
> Access privileges; see
<A
HREF="sql-grant.html"
>GRANT</A
> and
<A
HREF="sql-revoke.html"
>REVOKE</A
>
for details
</TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>reloptions</TT
></TD
><TD
><TT
CLASS="TYPE"
>text[]</TT
></TD
><TD
> </TD
><TD
> Access-method-specific options, as <SPAN
CLASS="QUOTE"
>"keyword=value"</SPAN
> strings
</TD
></TR
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></TABLE
></DIV
><P
> Several of the Boolean flags in <TT
CLASS="STRUCTNAME"
>pg_class</TT
> are maintained
lazily: they are guaranteed to be true if that's the correct state, but
may not be reset to false immediately when the condition is no longer
true. For example, <TT
CLASS="STRUCTFIELD"
>relhasindex</TT
> is set by
<TT
CLASS="COMMAND"
>CREATE INDEX</TT
>, but it is never cleared by
<TT
CLASS="COMMAND"
>DROP INDEX</TT
>. Instead, <TT
CLASS="COMMAND"
>VACUUM</TT
> clears
<TT
CLASS="STRUCTFIELD"
>relhasindex</TT
> if it finds the table has no indexes. This
arrangement avoids race conditions and improves concurrency.
</P
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