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| author | Jeff Davis <jdavis@postgresql.org> | 2020-06-11 11:58:16 -0700 |
|---|---|---|
| committer | Jeff Davis <jdavis@postgresql.org> | 2020-06-11 12:57:43 -0700 |
| commit | 92c58fd94801dd5c81ee20e26c5bb71ad64552a8 (patch) | |
| tree | 9bcddd92b5d49527ff0cbf4af561e2ca9a0cd7c3 /doc/src | |
| parent | 5940ffb221316ab73e6fdc780dfe9a07d4221ebb (diff) | |
| download | postgresql-92c58fd94801dd5c81ee20e26c5bb71ad64552a8.tar.gz postgresql-92c58fd94801dd5c81ee20e26c5bb71ad64552a8.zip | |
Rework HashAgg GUCs.
Eliminate enable_groupingsets_hash_disk, which was primarily useful
for testing grouping sets that use HashAgg and spill. Instead, hack
the table stats to convince the planner to choose hashed aggregation
for grouping sets that will spill to disk. Suggested by Melanie
Plageman.
Rename enable_hashagg_disk to hashagg_avoid_disk_plan, and invert the
meaning of on/off. The new name indicates more strongly that it only
affects the planner. Also, the word "avoid" is less definite, which
should avoid surprises when HashAgg still needs to use the
disk. Change suggested by Justin Pryzby, though I chose a different
GUC name.
Discussion: https://postgr.es/m/CAAKRu_aisiENMsPM2gC4oUY1hHG3yrCwY-fXUg22C6_MJUwQdA%40mail.gmail.com
Discussion: https://postgr.es/m/20200610021544.GA14879@telsasoft.com
Backpatch-through: 13
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 31 |
1 files changed, 8 insertions, 23 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 29088215603..783bf7a12ba 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -4546,23 +4546,6 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class=" </listitem> </varlistentry> - <varlistentry id="guc-enable-groupingsets-hash-disk" xreflabel="enable_groupingsets_hash_disk"> - <term><varname>enable_groupingsets_hash_disk</varname> (<type>boolean</type>) - <indexterm> - <primary><varname>enable_groupingsets_hash_disk</varname> configuration parameter</primary> - </indexterm> - </term> - <listitem> - <para> - Enables or disables the query planner's use of hashed aggregation plan - types for grouping sets when the total size of the hash tables is - expected to exceed <varname>work_mem</varname>. See <xref - linkend="queries-grouping-sets"/>. The default is - <literal>off</literal>. - </para> - </listitem> - </varlistentry> - <varlistentry id="guc-enable-hashagg" xreflabel="enable_hashagg"> <term><varname>enable_hashagg</varname> (<type>boolean</type>) <indexterm> @@ -4577,17 +4560,19 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class=" </listitem> </varlistentry> - <varlistentry id="guc-enable-hashagg-disk" xreflabel="enable_hashagg_disk"> - <term><varname>enable_hashagg_disk</varname> (<type>boolean</type>) + <varlistentry id="guc-hashagg-avoid-disk-plan" xreflabel="hashagg_avoid_disk_plan"> + <term><varname>hashagg_avoid_disk_plan</varname> (<type>boolean</type>) <indexterm> - <primary><varname>enable_hashagg_disk</varname> configuration parameter</primary> + <primary><varname>hashagg_avoid_disk_plan</varname> configuration parameter</primary> </indexterm> </term> <listitem> <para> - Enables or disables the query planner's use of hashed aggregation plan - types when the memory usage is expected to exceed - <varname>work_mem</varname>. The default is <literal>on</literal>. + If set to <literal>on</literal>, causes the planner to avoid choosing + hashed aggregation plans that are expected to use the disk. If hashed + aggregation is chosen, it may still require the use of disk at + execution time, even if this parameter is enabled. The default is + <literal>off</literal>. </para> </listitem> </varlistentry> |