From 445ce15702f701423a0fed3defe3a43662c7cd8d Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 7 Jan 2009 22:40:49 +0000
Subject: Create a third option named "partition" for constraint_exclusion, and
 make it the default.  This setting enables constraint exclusion checks only
 for appendrel members (ie, inheritance children and UNION ALL arms), which
 are the cases in which constraint exclusion is most likely to be useful. 
 Avoiding the overhead for simple queries that are unlikely to benefit should
 bring the cost down to the point where this is a reasonable default setting.
 Per today's discussion.

---
 src/backend/utils/misc/guc.c | 39 +++++++++++++++++++++++++++++----------
 1 file changed, 29 insertions(+), 10 deletions(-)

(limited to 'src/backend/utils/misc/guc.c')

diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 479279cdc43..22cfbff6105 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.490 2009/01/06 16:39:52 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.491 2009/01/07 22:40:49 tgl Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -311,6 +311,23 @@ static const struct config_enum_entry backslash_quote_options[] = {
 	{NULL, 0, false}
 };
 
+/*
+ * Although only "on", "off", and "partition" are documented, we
+ * accept all the likely variants of "on" and "off".
+ */
+static const struct config_enum_entry constraint_exclusion_options[] = {
+	{"partition", CONSTRAINT_EXCLUSION_PARTITION, false},
+	{"on", CONSTRAINT_EXCLUSION_ON, false},
+	{"off", CONSTRAINT_EXCLUSION_OFF, false},
+	{"true", CONSTRAINT_EXCLUSION_ON, true},
+	{"false", CONSTRAINT_EXCLUSION_OFF, true},
+	{"yes", CONSTRAINT_EXCLUSION_ON, true},
+	{"no", CONSTRAINT_EXCLUSION_OFF, true},
+	{"1", CONSTRAINT_EXCLUSION_ON, true},
+	{"0", CONSTRAINT_EXCLUSION_OFF, true},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -635,15 +652,6 @@ static struct config_bool ConfigureNamesBool[] =
 		&enable_hashjoin,
 		true, NULL, NULL
 	},
-	{
-		{"constraint_exclusion", PGC_USERSET, QUERY_TUNING_OTHER,
-			gettext_noop("Enables the planner to use constraints to optimize queries."),
-			gettext_noop("Child table scans will be skipped if their "
-					   "constraints guarantee that no rows match the query.")
-		},
-		&constraint_exclusion,
-		false, NULL, NULL
-	},
 	{
 		{"geqo", PGC_USERSET, QUERY_TUNING_GEQO,
 			gettext_noop("Enables genetic query optimization."),
@@ -2521,6 +2529,17 @@ static struct config_enum ConfigureNamesEnum[] =
 		NOTICE, client_message_level_options, NULL, NULL
 	},
 
+	{
+		{"constraint_exclusion", PGC_USERSET, QUERY_TUNING_OTHER,
+			gettext_noop("Enables the planner to use constraints to optimize queries."),
+			gettext_noop("Table scans will be skipped if their constraints"
+						 " guarantee that no rows match the query.")
+		},
+		&constraint_exclusion,
+		CONSTRAINT_EXCLUSION_PARTITION, constraint_exclusion_options,
+		NULL, NULL
+	},
+
 	{
 		{"default_transaction_isolation", PGC_USERSET, CLIENT_CONN_STATEMENT,
 			gettext_noop("Sets the transaction isolation level of each new transaction."),
-- 
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