diff options
| -rw-r--r-- | doc/src/sgml/func.sgml | 28 | ||||
| -rw-r--r-- | doc/src/sgml/maintenance.sgml | 5 |
2 files changed, 31 insertions, 2 deletions
diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index cc186a2547d..aac9e4b4bbf 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -23394,6 +23394,31 @@ SELECT collation for ('foo' COLLATE "de_DE"); a subtransaction ID. </para></entry> </row> + + <row> + <entry role="func_table_entry"><para role="func_signature"> + <indexterm> + <primary>pg_get_multixact_members</primary> + </indexterm> + <function>pg_get_multixact_members</function> ( <parameter>multixid</parameter> <type>xid</type> ) + <returnvalue>setof record</returnvalue> + ( <parameter>xid</parameter> <type>xid</type>, + <parameter>mode</parameter> <type>text</type> ) + </para> + <para> + Returns the transaction ID and lock mode for each member of the + specified multixact ID. The lock modes <literal>forupd</literal>, + <literal>fornokeyupd</literal>, <literal>sh</literal>, and + <literal>keysh</literal> correspond to the row-level locks + <literal>FOR UPDATE</literal>, <literal>FOR NO KEY UPDATE</literal>, + <literal>FOR SHARE</literal>, and <literal>FOR KEY SHARE</literal>, + respectively, as described in <xref linkend="locking-rows"/>. Two + additional modes are specific to multixacts: + <literal>nokeyupd</literal>, used by updates that do not modify key + columns, and <literal>upd</literal>, used by updates or deletes that + modify key columns. + </para></entry> + </row> </tbody> </tgroup> </table> @@ -23402,7 +23427,8 @@ SELECT collation for ('foo' COLLATE "de_DE"); The internal transaction ID type <type>xid</type> is 32 bits wide and wraps around every 4 billion transactions. However, the functions shown in <xref linkend="functions-pg-snapshot"/>, except - <function>age</function> and <function>mxid_age</function>, use a + <function>age</function>, <function>mxid_age</function>, and + <function>pg_get_multixact_members</function>, use a 64-bit type <type>xid8</type> that does not wrap around during the life of an installation, and can be converted to <type>xid</type> by casting if required. The data type <type>pg_snapshot</type> stores information about diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml index 0aac6867d07..5e6a9bf5ebe 100644 --- a/doc/src/sgml/maintenance.sgml +++ b/doc/src/sgml/maintenance.sgml @@ -690,7 +690,10 @@ HINT: Stop the postmaster and vacuum that database in single-user mode. careful aging management, storage cleanup, and wraparound handling. There is a separate storage area which holds the list of members in each multixact, which also uses a 32-bit counter and which must also - be managed. + be managed. The system function + <function>pg_get_multixact_members()</function> described in + <xref linkend="functions-pg-snapshot"/> can be used to examine the + transaction IDs associated with a multixact ID. </para> <para> |