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.

diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index e464e66878a5fbf580641ca87e258dc71a6151ed..f81c920d26d3afcf6a8b6da30810b2270c912533 100644 (file)
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.230 2004/01/10 23:28:43 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.231 2004/01/21 23:33:34 tgl Exp $
 -->
 
 <Chapter Id="runtime">
@@ -1404,23 +1404,25 @@ SET ENABLE_SEQSCAN TO OFF;
      </varlistentry>
 
      <varlistentry>
-      <term><varname>geqo_effort</varname> (<type>integer</type>)</term>
-      <term><varname>geqo_generations</varname> (<type>integer</type>)</term>
       <term><varname>geqo_pool_size</varname> (<type>integer</type>)</term>
+      <term><varname>geqo_generations</varname> (<type>integer</type>)</term>
+      <term><varname>geqo_effort</varname> (<type>integer</type>)</term>
       <term><varname>geqo_selection_bias</varname> (<type>floating point</type>)</term>
       <listitem>
        <para>
         Various tuning parameters for the genetic query optimization
-        algorithm: The pool size is the number of individuals in one
+        algorithm. The pool size is the number of individuals in one
         population. Valid values are between 128 and 1024. If it is set
         to 0 (the default) a pool size of 2^(QS+1), where QS is the
-        number of <literal>FROM</> items in the query, is taken. The effort is used
-        to calculate a default for generations. Valid values are between
-        1 and 80, 40 being the default. Generations specifies the number
-        of iterations in the algorithm. The number must be a positive
-        integer. If 0 is specified then <literal>Effort *
-        Log2(PoolSize)</literal> is used. The run time of the algorithm
-        is roughly proportional to the sum of pool size and generations.
+        number of <literal>FROM</> items in the query, is used.
+       Generations specifies the number of iterations of the algorithm.
+       The value must be a positive integer. If 0 is specified then
+       <literal>Effort * Log2(PoolSize)</literal> is used.
+       The run time of the algorithm is roughly proportional to the sum of
+       pool size and generations.
+       <varname>geqo_effort</varname> is only used in computing the default
+       generations setting, as just described.  The default value is 40,
+       and the allowed range 1 to 100.
         The selection bias is the selective pressure within the
         population. Values can be from 1.50 to 2.00; the latter is the
         default.

diff --git a/src/backend/optimizer/geqo/geqo_main.c b/src/backend/optimizer/geqo/geqo_main.c
index 9b16c4a06e6ee140fc892a982de8bc45289834ba..6a883fa313799ac8e26e570967deea764a61d414 100644 (file)
--- 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 45bbfc96ea0b0e5b2d67210f5e97b1a0295c893b..2633bf9e4d3ec0573560de0eca5f1e60d92cdb4d 100644 (file)
--- 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 $
  *
  *--------------------------------------------------------------------
  */
@@ -931,23 +931,23 @@ static struct config_int ConfigureNamesInt[] =
                &Geqo_pool_size,
                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 98d4d76d3ae6bd65a778c1592e030ed18508a8bf..0fdf6b2e99fd2e46534ee75dd3a3d69704078bec 100644 (file)
--- 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 249b477223031ccee00c5d175ee18ef4ff749d78..caa05f52ee971f9e53fd924440258ef22becf56d 100644 (file)
--- 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