diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 69 | ||||
| -rw-r--r-- | doc/src/sgml/contrib.sgml | 1 | ||||
| -rw-r--r-- | doc/src/sgml/filelist.sgml | 1 | ||||
| -rw-r--r-- | doc/src/sgml/oldsnapshot.sgml | 33 |
4 files changed, 0 insertions, 104 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 694d667bf97..f0a50a5f9ad 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -2709,65 +2709,6 @@ include_dir 'conf.d' </para> </listitem> </varlistentry> - - <varlistentry id="guc-old-snapshot-threshold" xreflabel="old_snapshot_threshold"> - <term><varname>old_snapshot_threshold</varname> (<type>integer</type>) - <indexterm> - <primary><varname>old_snapshot_threshold</varname> configuration parameter</primary> - </indexterm> - </term> - <listitem> - <para> - Sets the minimum amount of time that a query snapshot can be used - without risk of a <quote>snapshot too old</quote> error occurring - when using the snapshot. Data that has been dead for longer than - this threshold is allowed to be vacuumed away. This can help - prevent bloat in the face of snapshots which remain in use for a - long time. To prevent incorrect results due to cleanup of data which - would otherwise be visible to the snapshot, an error is generated - when the snapshot is older than this threshold and the snapshot is - used to read a page which has been modified since the snapshot was - built. - </para> - - <para> - If this value is specified without units, it is taken as minutes. - A value of <literal>-1</literal> (the default) disables this feature, - effectively setting the snapshot age limit to infinity. - This parameter can only be set at server start. - </para> - - <para> - Useful values for production work probably range from a small number - of hours to a few days. Small values (such as <literal>0</literal> or - <literal>1min</literal>) are only allowed because they may sometimes be - useful for testing. While a setting as high as <literal>60d</literal> is - allowed, please note that in many workloads extreme bloat or - transaction ID wraparound may occur in much shorter time frames. - </para> - - <para> - When this feature is enabled, freed space at the end of a relation - cannot be released to the operating system, since that could remove - information needed to detect the <quote>snapshot too old</quote> - condition. All space allocated to a relation remains associated with - that relation for reuse only within that relation unless explicitly - freed (for example, with <command>VACUUM FULL</command>). - </para> - - <para> - This setting does not attempt to guarantee that an error will be - generated under any particular circumstances. In fact, if the - correct results can be generated from (for example) a cursor which - has materialized a result set, no error will be generated even if the - underlying rows in the referenced table have been vacuumed away. - Some tables cannot safely be vacuumed early, and so will not be - affected by this setting, such as system catalogs. For such tables - this setting will neither reduce bloat nor create a possibility - of a <quote>snapshot too old</quote> error on scanning. - </para> - </listitem> - </varlistentry> </variablelist> </sect2> </sect1> @@ -4783,16 +4724,6 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class=" until it eventually reaches the primary. Standbys make no other use of feedback they receive other than to pass upstream. </para> - <para> - This setting does not override the behavior of - <varname>old_snapshot_threshold</varname> on the primary; a snapshot on the - standby which exceeds the primary's age threshold can become invalid, - resulting in cancellation of transactions on the standby. This is - because <varname>old_snapshot_threshold</varname> is intended to provide an - absolute limit on the time which dead rows can contribute to bloat, - which would otherwise be violated because of the configuration of a - standby. - </para> </listitem> </varlistentry> diff --git a/doc/src/sgml/contrib.sgml b/doc/src/sgml/contrib.sgml index 922421a8971..ab7e38b52a5 100644 --- a/doc/src/sgml/contrib.sgml +++ b/doc/src/sgml/contrib.sgml @@ -150,7 +150,6 @@ CREATE EXTENSION <replaceable>extension_name</replaceable>; &isn; &lo; <ree; - &oldsnapshot; &pageinspect; &passwordcheck; &pgbuffercache; diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml index 63b0fc2a469..e3d94a62b3f 100644 --- a/doc/src/sgml/filelist.sgml +++ b/doc/src/sgml/filelist.sgml @@ -138,7 +138,6 @@ <!ENTITY lo SYSTEM "lo.sgml"> <!ENTITY ltree SYSTEM "ltree.sgml"> <!ENTITY oid2name SYSTEM "oid2name.sgml"> -<!ENTITY oldsnapshot SYSTEM "oldsnapshot.sgml"> <!ENTITY pageinspect SYSTEM "pageinspect.sgml"> <!ENTITY passwordcheck SYSTEM "passwordcheck.sgml"> <!ENTITY pgbuffercache SYSTEM "pgbuffercache.sgml"> diff --git a/doc/src/sgml/oldsnapshot.sgml b/doc/src/sgml/oldsnapshot.sgml deleted file mode 100644 index 2e37087738b..00000000000 --- a/doc/src/sgml/oldsnapshot.sgml +++ /dev/null @@ -1,33 +0,0 @@ -<!-- doc/src/sgml/oldsnapshot.sgml --> - -<sect1 id="oldsnapshot" xreflabel="old_snapshot"> - <title>old_snapshot — inspect <literal>old_snapshot_threshold</literal> state</title> - - <indexterm zone="oldsnapshot"> - <primary>old_snapshot</primary> - </indexterm> - - <para> - The <filename>old_snapshot</filename> module allows inspection - of the server state that is used to implement - <xref linkend="guc-old-snapshot-threshold" />. - </para> - - <sect2 id="oldsnapshot-functions"> - <title>Functions</title> - - <variablelist> - <varlistentry> - <term><function>pg_old_snapshot_time_mapping(array_offset OUT int4, end_timestamp OUT timestamptz, newest_xmin OUT xid) returns setof record</function></term> - <listitem> - <para> - Returns all of the entries in the server's timestamp to XID mapping. - Each entry represents the newest xmin of any snapshot taken in the - corresponding minute. - </para> - </listitem> - </varlistentry> - </variablelist> - </sect2> - -</sect1> |