-<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.213 2007/11/05 14:51:08 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/datatype.sgml,v 1.214 2007/11/05 16:45:52 momjian Exp $ -->
<chapter id="datatype">
<title id="datatype-title">Data Types</title>
</sect1>
- <sect1 id="datatype-txid-snapshot">
- <title>Transaction Snapshot Type</title>
-
- <indexterm zone="datatype-txid-snapshot">
- <primary>txid_snapshot</primary>
- </indexterm>
-
- <para>
- The data type <type>txid_snapshot</type> stores info about transaction ID
- visibility at a particular moment in time. The components are
- described in <xref linkend="datatype-txid-snapshot-parts">.
- </para>
-
- <table id="datatype-txid-snapshot-parts">
- <title>Snapshot components</title>
- <tgroup cols="2">
- <thead>
- <row>
- <entry>Name</entry>
- <entry>Query Function</entry>
- <entry>Description</entry>
- </row>
- </thead>
-
- <tbody>
-
- <row>
- <entry><type>xmin</type></entry>
- <entry>txid_snapshot_xmin()</entry>
- <entry>
- Earliest transaction ID that is still active. All earlier
- transactions will either be committed and visible, or rolled
- back and dead.
- </entry>
- </row>
-
- <row>
- <entry><type>xmax</type></entry>
- <entry>txid_snapshot_xmax()</entry>
- <entry>
- Next unassigned txid. All txids later than this one are
- unassigned, and thus invisible.
- </entry>
- </row>
-
- <row>
- <entry><type>xip_list</type></entry>
- <entry>txid_snapshot_xip()</entry>
- <entry>
- Active txids at the time of snapshot. All of them are between
- xmin and xmax. A txid that is <literal>xmin <= txid <
- xmax</literal> and not in this list is visible.
- </entry>
- </row>
-
- </tbody>
- </tgroup>
- </table>
-
- <para>
- Snapshot's textual representation is <literal>[xmin]:[xmax]:[xip_list]</literal>
- for example <literal>10:20:10,14,15</literal> means
- <literal>xmin=10 xmax=20 xip_list=10,14,15</literal>.
- </para>
-
- <para>
- Functions for getting and querying transaction ids and snapshots are
- described in <xref linkend="functions-txid">.
- </para>
- </sect1>
-
<sect1 id="datatype-uuid">
<title><acronym>UUID</acronym> Type</title>
-<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.407 2007/11/05 14:51:08 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/func.sgml,v 1.408 2007/11/05 16:45:52 momjian Exp $ -->
<chapter id="functions">
<title>Functions and Operators</title>
<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">
which transactions were committed between two snapshots.
</para>
+ <para>
+ The data type <type>txid_snapshot</type> stores info about transaction ID
+ visibility at a particular moment in time. The components are
+ described in <xref linkend="datatype-txid-snapshot-parts">.
+ </para>
+
+ <table id="datatype-txid-snapshot-parts">
+ <title>Snapshot components</title>
+ <tgroup cols="2">
+ <thead>
+ <row>
+ <entry>Name</entry>
+ <entry>Query Function</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+
+ <tbody>
+
+ <row>
+ <entry><type>xmin</type></entry>
+ <entry>txid_snapshot_xmin()</entry>
+ <entry>
+ Earliest transaction ID that is still active. All earlier
+ transactions will either be committed and visible, or rolled
+ back and dead.
+ </entry>
+ </row>
+
+ <row>
+ <entry><type>xmax</type></entry>
+ <entry>txid_snapshot_xmax()</entry>
+ <entry>
+ Next unassigned txid. All txids later than this one are
+ unassigned, and thus invisible.
+ </entry>
+ </row>
+
+ <row>
+ <entry><type>xip_list</type></entry>
+ <entry>txid_snapshot_xip()</entry>
+ <entry>
+ Active txids at the time of snapshot. All of them are between
+ xmin and xmax. A txid that is <literal>xmin <= txid <
+ xmax</literal> and not in this list is visible.
+ </entry>
+ </row>
+
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>
+ Snapshot's textual representation is <literal>[xmin]:[xmax]:[xip_list]</literal>
+ for example <literal>10:20:10,14,15</literal> means
+ <literal>xmin=10 xmax=20 xip_list=10,14,15</literal>.
+ </para>
+
</sect1>
<sect1 id="functions-admin">