diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/datatype.sgml | 8 | ||||
| -rw-r--r-- | doc/src/sgml/func.sgml | 80 |
2 files changed, 86 insertions, 2 deletions
diff --git a/doc/src/sgml/datatype.sgml b/doc/src/sgml/datatype.sgml index 67f96ce1f73..326e4570303 100644 --- a/doc/src/sgml/datatype.sgml +++ b/doc/src/sgml/datatype.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.209 2007/08/31 04:52:29 momjian Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.210 2007/10/13 23:06:26 tgl Exp $ --> <chapter id="datatype"> <title id="datatype-title">Data Types</title> @@ -247,6 +247,12 @@ </row> <row> + <entry><type>txid_snapshot</type></entry> + <entry></entry> + <entry>user-level transaction ID snapshot</entry> + </row> + + <row> <entry><type>uuid</type></entry> <entry></entry> <entry>universally unique identifier</entry> diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml index 0eeb1545d98..8d4f4179ac8 100644 --- a/doc/src/sgml/func.sgml +++ b/doc/src/sgml/func.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.400 2007/10/11 02:43:55 momjian Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.401 2007/10/13 23:06:26 tgl Exp $ --> <chapter id="functions"> <title>Functions and Operators</title> @@ -12048,6 +12048,84 @@ SELECT pg_type_is_visible('myschema.widget'::regtype); databases within each cluster and their descriptions are stored globally as well. </para> + + <indexterm> + <primary>txid_current</primary> + </indexterm> + + <indexterm> + <primary>txid_current_snapshot</primary> + </indexterm> + + <indexterm> + <primary>txid_snapshot_xmin</primary> + </indexterm> + + <indexterm> + <primary>txid_snapshot_xmax</primary> + </indexterm> + + <indexterm> + <primary>txid_snapshot_xip</primary> + </indexterm> + + <indexterm> + <primary>txid_visible_in_snapshot</primary> + </indexterm> + + <para> + The functions shown in <xref linkend="functions-txid-snapshot"> + export server internal transaction info to user level. + </para> + + <table id="functions-txid-snapshot"> + <title>Transaction IDs and snapshots</title> + <tgroup cols="3"> + <thead> + <row><entry>Name</entry> <entry>Return Type</entry> <entry>Description</entry></row> + </thead> + + <tbody> + <row> + <entry><literal><function>txid_current</function>()</literal></entry> + <entry><type>bigint</type></entry> + <entry>get current transaction ID</entry> + </row> + <row> + <entry><literal><function>txid_current_snapshot</function>()</literal></entry> + <entry><type>txid_snapshot</type></entry> + <entry>get current snapshot</entry> + </row> + <row> + <entry><literal><function>txid_snapshot_xmin</function>(<parameter>txid_snapshot</parameter>)</literal></entry> + <entry><type>bigint</type></entry> + <entry>get xmin of snapshot</entry> + </row> + <row> + <entry><literal><function>txid_snapshot_xmax</function>(<parameter>txid_snapshot</parameter>)</literal></entry> + <entry><type>bigint</type></entry> + <entry>get xmax of snapshot</entry> + </row> + <row> + <entry><literal><function>txid_snapshot_xip</function>(<parameter>txid_snapshot</parameter>)</literal></entry> + <entry><type>setof bigint</type></entry> + <entry>get in-progress transaction IDs in snapshot</entry> + </row> + <row> + <entry><literal><function>txid_visible_in_snapshot</function>(<parameter>bigint</parameter>, <parameter>txid_snapshot</parameter>)</literal></entry> + <entry><type>boolean</type></entry> + <entry>is transaction ID visible in snapshot?</entry> + </row> + </tbody> + </tgroup> + </table> + + <para> + The internal transaction ID type (<type>xid</>) is 32 bits wide and so + it wraps around every 4 billion transactions. However, these functions + export a 64-bit format that is extended with an <quote>epoch</> counter + so that it will not wrap around for the life of an installation. + </para> </sect1> <sect1 id="functions-admin"> |