diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/runtime.sgml | 24 |
1 files changed, 13 insertions, 11 deletions
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml index e464e66878a..f81c920d26d 100644 --- 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. |