Add an 'enable_material' GUC.
The logic for determining whether to materialize has been significantly overhauled for 9.0. In case there should be any doubt about whether materialization is a win in any particular case, this should provide a convenient way of seeing what happens without it; but even with enable_material turned off, we still materialize in cases where it is required for correctness. Thanks to Tom Lane for the review.
This commit is contained in:
Robert Haas
parent
9287567eff
commit
5b89ef384c
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@ -1,4 +1,4 @@
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<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.267 2010/04/16 21:46:07 rhaas Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.268 2010/04/19 00:55:25 rhaas Exp $ -->
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<chapter Id="runtime-config">
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<title>Server Configuration</title>
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@ -2020,6 +2020,22 @@ SET ENABLE_SEQSCAN TO OFF;
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</listitem>
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</varlistentry>
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<varlistentry id="guc-enable-material" xreflabel="enable_material">
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<term><varname>enable_material</varname> (<type>boolean</type>)</term>
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<indexterm>
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<primary><varname>enable_material</> configuration parameter</primary>
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</indexterm>
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<listitem>
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<para>
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Enables or disables the query planner's use of materialization.
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It is impossible to suppress materialization entirely,
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but turning this variable off prevents the planner from inserting
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materialize nodes except in cases where it is required for correctness.
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The default is <literal>on</>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry id="guc-enable-mergejoin" xreflabel="enable_mergejoin">
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<term><varname>enable_mergejoin</varname> (<type>boolean</type>)</term>
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<indexterm>
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@ -59,7 +59,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.216 2010/02/26 02:00:44 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/path/costsize.c,v 1.217 2010/04/19 00:55:25 rhaas Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -114,6 +114,7 @@ bool enable_tidscan = true;
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bool enable_sort = true;
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bool enable_hashagg = true;
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bool enable_nestloop = true;
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bool enable_material = true;
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bool enable_mergejoin = true;
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bool enable_hashjoin = true;
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@ -1852,8 +1853,11 @@ cost_mergejoin(MergePath *path, PlannerInfo *root, SpecialJoinInfo *sjinfo)
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mat_inner_cost = inner_run_cost +
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cpu_operator_cost * inner_path_rows * rescanratio;
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/* Prefer materializing if it looks cheaper */
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if (mat_inner_cost < bare_inner_cost)
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/*
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* Prefer materializing if it looks cheaper, unless the user has asked
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* to suppress materialization.
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*/
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if (enable_material && mat_inner_cost < bare_inner_cost)
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path->materialize_inner = true;
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/*
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@ -1867,6 +1871,10 @@ cost_mergejoin(MergePath *path, PlannerInfo *root, SpecialJoinInfo *sjinfo)
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* merge joins can *preserve* the order of their inputs, so they can be
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* selected as the input of a mergejoin, and they don't support
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* mark/restore at present.
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*
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* We don't test the value of enable_material here, because materialization
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* is required for correctness in this case, and turning it off does not
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* entitle us to deliver an invalid plan.
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*/
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else if (innersortkeys == NIL &&
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!ExecSupportsMarkRestore(inner_path->pathtype))
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@ -1878,8 +1886,11 @@ cost_mergejoin(MergePath *path, PlannerInfo *root, SpecialJoinInfo *sjinfo)
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* pass can be done on-the-fly if it doesn't have to support mark/restore.
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* We don't try to adjust the cost estimates for this consideration,
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* though.
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*
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* Since materialization is a performance optimization in this case, rather
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* than necessary for correctness, we skip it if enable_material is off.
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*/
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else if (innersortkeys != NIL &&
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else if (enable_material && innersortkeys != NIL &&
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relation_byte_size(inner_path_rows, inner_path->parent->width) >
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(work_mem * 1024L))
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path->materialize_inner = true;
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.132 2010/03/28 22:59:32 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.133 2010/04/19 00:55:25 rhaas Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -437,10 +437,12 @@ match_unsorted_outer(PlannerInfo *root,
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else if (nestjoinOK)
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{
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/*
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* Consider materializing the cheapest inner path, unless it is one
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* that materializes its output anyway.
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* Consider materializing the cheapest inner path, unless
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* enable_material is off or the path in question materializes its
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* output anyway.
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*/
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if (!ExecMaterializesOutput(inner_cheapest_total->pathtype))
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if (enable_material &&
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!ExecMaterializesOutput(inner_cheapest_total->pathtype))
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matpath = (Path *)
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create_material_path(innerrel, inner_cheapest_total);
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.161 2010/02/26 02:00:46 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.162 2010/04/19 00:55:25 rhaas Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -578,9 +578,11 @@ build_subplan(PlannerInfo *root, Plan *plan, List *rtable, List *rowmarks,
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* is pointless for a direct-correlated subplan, since we'd have to
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* recompute its results each time anyway. For uncorrelated/undirect
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* correlated subplans, we add Material unless the subplan's top plan
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* node would materialize its output anyway.
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* node would materialize its output anyway. Also, if enable_material
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* is false, then the user does not want us to materialize anything
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* unnecessarily, so we don't.
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*/
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else if (splan->parParam == NIL &&
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else if (splan->parParam == NIL && enable_material &&
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!ExecMaterializesOutput(nodeTag(plan)))
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plan = materialize_finished_plan(plan);
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@ -10,7 +10,7 @@
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* Written by Peter Eisentraut <peter_e@gmx.net>.
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.547 2010/04/12 09:52:29 heikki Exp $
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* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.548 2010/04/19 00:55:25 rhaas Exp $
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*
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*--------------------------------------------------------------------
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*/
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@ -643,6 +643,14 @@ static struct config_bool ConfigureNamesBool[] =
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&enable_hashagg,
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true, NULL, NULL
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},
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{
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{"enable_material", PGC_USERSET, QUERY_TUNING_METHOD,
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gettext_noop("Enables the planner's use of materialization."),
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NULL
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},
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&enable_material,
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true, NULL, NULL
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},
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{
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{"enable_nestloop", PGC_USERSET, QUERY_TUNING_METHOD,
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gettext_noop("Enables the planner's use of nested-loop join plans."),
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@ -206,6 +206,7 @@
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#enable_hashagg = on
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#enable_hashjoin = on
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#enable_indexscan = on
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#enable_material = on
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#enable_mergejoin = on
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#enable_nestloop = on
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#enable_seqscan = on
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.100 2010/01/02 16:58:07 momjian Exp $
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* $PostgreSQL: pgsql/src/include/optimizer/cost.h,v 1.101 2010/04/19 00:55:26 rhaas Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -57,6 +57,7 @@ extern bool enable_tidscan;
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extern bool enable_sort;
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extern bool enable_hashagg;
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extern bool enable_nestloop;
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extern bool enable_material;
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extern bool enable_mergejoin;
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extern bool enable_hashjoin;
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extern int constraint_exclusion;
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@ -5,12 +5,13 @@ SELECT name, setting FROM pg_settings WHERE name LIKE 'enable%';
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enable_hashagg | on
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enable_hashjoin | on
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enable_indexscan | on
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enable_material | on
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enable_mergejoin | on
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enable_nestloop | on
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enable_seqscan | on
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enable_sort | on
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enable_tidscan | on
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(9 rows)
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(10 rows)
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CREATE TABLE foo2(fooid int, f2 int);
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INSERT INTO foo2 VALUES(1, 11);
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