Repair error apparently introduced in the initial coding of GUC: the

default value for geqo_effort is supposed to be 40, not 1.  The actual
'genetic' component of the GEQO algorithm has been practically disabled
since 7.1 because of this mistake.  Improve documentation while at it.

4 files changed, 42 insertions, 27 deletions

diff --git a/src/backend/optimizer/geqo/geqo_main.c b/src/backend/optimizer/geqo/geqo_main.c
index 9b16c4a06e6..6a883fa3137 100644
--- a/src/backend/optimizer/geqo/geqo_main.c
+++ b/src/backend/optimizer/geqo/geqo_main.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_main.c,v 1.41 2003/11/29 19:51:50 pgsql Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/geqo/geqo_main.c,v 1.42 2004/01/21 23:33:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -38,13 +38,13 @@
  * Configuration options
  */
 int			Geqo_pool_size;
-int			Geqo_effort;
 int			Geqo_generations;
+int			Geqo_effort;
 double		Geqo_selection_bias;
 
 
 static int	gimme_pool_size(int nr_rel);
-static int	gimme_number_generations(int pool_size, int effort);
+static int	gimme_number_generations(int pool_size);
 
 /* define edge recombination crossover [ERX] per default */
 #if !defined(ERX) && \
@@ -92,7 +92,7 @@ geqo(Query *root, int number_of_rels, List *initial_rels)
 
 /* set GA parameters */
 	pool_size = gimme_pool_size(number_of_rels);
-	number_generations = gimme_number_generations(pool_size, Geqo_effort);
+	number_generations = gimme_number_generations(pool_size);
 	status_interval = 10;
 
 /* allocate genetic pool memory */
@@ -284,7 +284,7 @@ gimme_pool_size(int nr_rel)
 {
 	double		size;
 
-	if (Geqo_pool_size != 0)
+	if (Geqo_pool_size > 0)
 		return Geqo_pool_size;
 
 	size = pow(2.0, nr_rel + 1.0);
@@ -305,10 +305,20 @@ gimme_pool_size(int nr_rel)
  * = Effort * Log2(PoolSize)
  */
 static int
-gimme_number_generations(int pool_size, int effort)
+gimme_number_generations(int pool_size)
 {
-	if (Geqo_generations <= 0)
-		return effort * (int) ceil(log((double) pool_size) / log(2.0));
-	else
+	double		gens;
+
+	if (Geqo_generations > 0)
 		return Geqo_generations;
+
+	gens = Geqo_effort * log((double) pool_size) / log(2.0);
+
+	/* bound it to a sane range */
+	if (gens <= 0)
+		gens = 1;
+	else if (gens > 10000)
+		gens = 10000;
+
+	return (int) ceil(gens);
 }
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 45bbfc96ea0..2633bf9e4d3 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 1.177 2004/01/19 19:04:40 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.178 2004/01/21 23:33:34 tgl Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -932,22 +932,22 @@ static struct config_int ConfigureNamesInt[] =
 		DEFAULT_GEQO_POOL_SIZE, 0, MAX_GEQO_POOL_SIZE, NULL, NULL
 	},
 	{
-		{"geqo_effort", PGC_USERSET, QUERY_TUNING_GEQO,
-			gettext_noop("GEQO: effort is used to calculate a default for generations."),
-			NULL
-		},
-		&Geqo_effort,
-		1, 1, INT_MAX, NULL, NULL
-	},
-	{
 		{"geqo_generations", PGC_USERSET, QUERY_TUNING_GEQO,
-			gettext_noop("GEQO: number of iterations in the algorithm."),
-			gettext_noop("The number must be a positive integer. If 0 is "
+			gettext_noop("GEQO: number of iterations of the algorithm."),
+			gettext_noop("The value must be a positive integer. If 0 is "
 						 "specified then effort * log2(poolsize) is used.")
 		},
 		&Geqo_generations,
 		0, 0, INT_MAX, NULL, NULL
 	},
+	{
+		{"geqo_effort", PGC_USERSET, QUERY_TUNING_GEQO,
+			gettext_noop("GEQO: effort is used to set the default for generations."),
+			NULL
+		},
+		&Geqo_effort,
+		DEFAULT_GEQO_EFFORT, MIN_GEQO_EFFORT, MAX_GEQO_EFFORT, NULL, NULL
+	},
 
 	{
 		{"deadlock_timeout", PGC_SIGHUP, LOCK_MANAGEMENT,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 98d4d76d3ae..0fdf6b2e99f 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -123,10 +123,10 @@
 
 #geqo = true
 #geqo_threshold = 11
-#geqo_effort = 1
-#geqo_generations = 0
 #geqo_pool_size = 0		# default based on tables in statement,
 				# range 128-1024
+#geqo_generations = 0		# use default: effort * log2(pool_size)
+#geqo_effort = 40		# range 1-100
 #geqo_selection_bias = 2.0	# range 1.5-2.0
 
 # - Other Planner Options -
diff --git a/src/include/optimizer/geqo.h b/src/include/optimizer/geqo.h
index 249b4772230..caa05f52ee9 100644
--- a/src/include/optimizer/geqo.h
+++ b/src/include/optimizer/geqo.h
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/geqo.h,v 1.33 2003/11/29 22:41:07 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/geqo.h,v 1.34 2004/01/21 23:33:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -44,22 +44,27 @@
 
 /*
  * Configuration options
+ *
+ * If you change these, update backend/utils/misc/postgresql.sample.conf
  */
-/* If you change these, update backend/utils/misc/postgresql.sample.conf */
 extern int	Geqo_pool_size;
 
 #define DEFAULT_GEQO_POOL_SIZE 0	/* = default based on no. of relations. */
 #define MIN_GEQO_POOL_SIZE 128
 #define MAX_GEQO_POOL_SIZE 1024
 
-extern int	Geqo_effort;		/* 1 .. inf, only used to calculate
-								 * generations default */
 extern int	Geqo_generations;	/* 1 .. inf, or 0 to use default based on
 								 * pool size */
 
+extern int	Geqo_effort;		/* only used to calculate default for
+								 * generations */
+
+#define DEFAULT_GEQO_EFFORT 40
+#define MIN_GEQO_EFFORT 1
+#define MAX_GEQO_EFFORT 100
+
 extern double Geqo_selection_bias;
 
-/* If you change these, update backend/utils/misc/postgresql.sample.conf */
 #define DEFAULT_GEQO_SELECTION_BIAS 2.0
 #define MIN_GEQO_SELECTION_BIAS 1.5
 #define MAX_GEQO_SELECTION_BIAS 2.0