0001-Add-enable_partialsort-GUC-for-disabling-partial-sor.patch

From 3f05447e7feb99583336b381df60ff013a144bab Mon Sep 17 00:00:00 2001
From: Marti Raudsepp <marti@juffo.org>
Date: Mon, 13 Jan 2014 22:24:20 +0200
Subject: [PATCH] Add enable_partialsort GUC for disabling partial sorts

---
 doc/src/sgml/config.sgml                      | 13 +++++++++++++
 src/backend/optimizer/path/costsize.c         |  3 ++-
 src/backend/optimizer/path/pathkeys.c         |  1 +
 src/backend/utils/misc/guc.c                  | 10 ++++++++++
 src/backend/utils/misc/postgresql.conf.sample |  1 +
 src/include/optimizer/cost.h                  |  1 +
 6 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0f2f2bf..1995625 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2808,6 +2808,19 @@ include 'filename'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-enable-partialsort" xreflabel="enable_partialsort">
+      <term><varname>enable_partialsort</varname> (<type>boolean</type>)</term>
+      <indexterm>
+       <primary><varname>enable_partialsort</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        Enables or disables the query planner's use of partial sort steps.
+        The default is <literal>on</>.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-enable-tidscan" xreflabel="enable_tidscan">
       <term><varname>enable_tidscan</varname> (<type>boolean</type>)</term>
       <indexterm>
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index da64825..cefd480 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -112,6 +112,7 @@ bool		enable_indexonlyscan = true;
 bool		enable_bitmapscan = true;
 bool		enable_tidscan = true;
 bool		enable_sort = true;
+bool		enable_partialsort = true;
 bool		enable_hashagg = true;
 bool		enable_nestloop = true;
 bool		enable_material = true;
@@ -1329,7 +1330,7 @@ cost_sort(Path *path, PlannerInfo *root,
 	/*
 	 * Estimate number of groups which dataset is divided by presorted keys.
 	 */
-	if (presorted_keys > 0)
+	if (presorted_keys > 0 && enable_partialsort)
 	{
 		List *groupExprs = NIL;
 		ListCell *l;
diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c
index 55d8ef4..d5a1357 100644
--- a/src/backend/optimizer/path/pathkeys.c
+++ b/src/backend/optimizer/path/pathkeys.c
@@ -22,6 +22,7 @@
 #include "nodes/nodeFuncs.h"
 #include "nodes/plannodes.h"
 #include "optimizer/clauses.h"
+#include "optimizer/cost.h"
 #include "optimizer/pathnode.h"
 #include "optimizer/paths.h"
 #include "optimizer/tlist.h"
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 1217098..c3f2f29 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -1,3 +1,4 @@
+
 /*--------------------------------------------------------------------
  * guc.c
  *
@@ -724,6 +725,15 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 	{
+		{"enable_partialsort", PGC_USERSET, QUERY_TUNING_METHOD,
+			gettext_noop("Enables the planner's use of partial sort steps."),
+			NULL
+		},
+		&enable_partialsort,
+		true,
+		NULL, NULL, NULL
+	},
+	{
 		{"enable_hashagg", PGC_USERSET, QUERY_TUNING_METHOD,
 			gettext_noop("Enables the planner's use of hashed aggregation plans."),
 			NULL
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 27791cc..20072fb 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -270,6 +270,7 @@
 #enable_nestloop = on
 #enable_seqscan = on
 #enable_sort = on
+#enable_partialsort = on
 #enable_tidscan = on
 
 # - Planner Cost Constants -
diff --git a/src/include/optimizer/cost.h b/src/include/optimizer/cost.h
index 47aef12..30203c7 100644
--- a/src/include/optimizer/cost.h
+++ b/src/include/optimizer/cost.h
@@ -56,6 +56,7 @@ extern bool enable_indexonlyscan;
 extern bool enable_bitmapscan;
 extern bool enable_tidscan;
 extern bool enable_sort;
+extern bool enable_partialsort;
 extern bool enable_hashagg;
 extern bool enable_nestloop;
 extern bool enable_material;
-- 
1.8.5.2