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Allow the planner's estimate of the fraction of a cursor's rows that will be

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retrieved to be controlled through a GUC variable.

Robert Hell
This commit is contained in:
Tom Lane
2008-05-02 21:26:10 +00:00
parent cf9f6c8d8e
commit db147b3483
5 changed files with 58 additions and 8 deletions
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12
src/backend/utils/misc/guc.c
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@@ -10,7 +10,7 @@
* Written by Peter Eisentraut <peter_e@gmx.net>.
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.450 2008/05/01 19:55:40 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.451 2008/05/02 21:26:10 tgl Exp $
*
*--------------------------------------------------------------------
*/
@@ -1891,6 +1891,16 @@ static struct config_real ConfigureNamesReal[] =
DEFAULT_CPU_OPERATOR_COST, 0, DBL_MAX, NULL, NULL
},
{
{"cursor_tuple_fraction", PGC_USERSET, QUERY_TUNING_OTHER,
gettext_noop("Sets the planner's estimate of the fraction of "
"a cursor's rows that will be retrieved."),
NULL
},
&cursor_tuple_fraction,
DEFAULT_CURSOR_TUPLE_FRACTION, 0.0, 1.0, NULL, NULL
},
{
{"geqo_selection_bias", PGC_USERSET, QUERY_TUNING_GEQO,
gettext_noop("GEQO: selective pressure within the population."),

1
src/backend/utils/misc/postgresql.conf.sample
View File

@@ -219,6 +219,7 @@
#default_statistics_target = 10 # range 1-1000
#constraint_exclusion = off
#cursor_tuple_fraction = 0.1 # range 0.0-1.0
#from_collapse_limit = 8
#join_collapse_limit = 8 # 1 disables collapsing of explicit
# JOIN clauses