diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 39 | ||||
| -rw-r--r-- | doc/src/sgml/release-9.6.sgml | 2 |
2 files changed, 1 insertions, 40 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 4b265d9e40c..c13f60230f9 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -1505,45 +1505,6 @@ include_dir 'conf.d' </listitem> </varlistentry> - <varlistentry id="guc-replacement-sort-tuples" xreflabel="replacement_sort_tuples"> - <term><varname>replacement_sort_tuples</varname> (<type>integer</type>) - <indexterm> - <primary><varname>replacement_sort_tuples</> configuration parameter</primary> - </indexterm> - </term> - <listitem> - <para> - When the number of tuples to be sorted is smaller than this number, - a sort will produce its first output run using replacement selection - rather than quicksort. This may be useful in memory-constrained - environments where tuples that are input into larger sort operations - have a strong physical-to-logical correlation. Note that this does - not include input tuples with an <emphasis>inverse</emphasis> - correlation. It is possible for the replacement selection algorithm - to generate one long run that requires no merging, where use of the - default strategy would result in many runs that must be merged - to produce a final sorted output. This may allow sort - operations to complete sooner. - </para> - <para> - The default is 150,000 tuples. Note that higher values are typically - not much more effective, and may be counter-productive, since the - priority queue is sensitive to the size of available CPU cache, whereas - the default strategy sorts runs using a <firstterm>cache - oblivious</firstterm> algorithm. This property allows the default sort - strategy to automatically and transparently make effective use - of available CPU cache. - </para> - <para> - Setting <varname>maintenance_work_mem</varname> to its default - value usually prevents utility command external sorts (e.g., - sorts used by <command>CREATE INDEX</> to build B-Tree - indexes) from ever using replacement selection sort, unless the - input tuples are quite wide. - </para> - </listitem> - </varlistentry> - <varlistentry id="guc-autovacuum-work-mem" xreflabel="autovacuum_work_mem"> <term><varname>autovacuum_work_mem</varname> (<type>integer</type>) <indexterm> diff --git a/doc/src/sgml/release-9.6.sgml b/doc/src/sgml/release-9.6.sgml index dc811c4ca5d..09b6b902547 100644 --- a/doc/src/sgml/release-9.6.sgml +++ b/doc/src/sgml/release-9.6.sgml @@ -5140,7 +5140,7 @@ and many others in the same vein The new approach makes better use of the <acronym>CPU</> cache for typical cache sizes and data volumes. Where necessary, the behavior can be adjusted via the new configuration parameter - <xref linkend="guc-replacement-sort-tuples">. + <literal>replacement_sort_tuples</literal>. </para> </listitem> |