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Commitcdf0231

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Create a function variable "join_search_hook" to let plugins override the
join search order portion of the planner; this is specifically intended tosimplify developing a replacement for GEQO planning. Patch by JuliusStroffek, editorialized on by me. I renamed make_one_rel_by_joins tostandard_join_search and make_rels_by_joins to join_search_one_level to betterreflect their place within this scheme.
1 parent149af06 commitcdf0231

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4 files changed

+55
-26
lines changed

4 files changed

+55
-26
lines changed

‎src/backend/optimizer/README‎

Lines changed: 7 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -292,16 +292,17 @@ planner()
292292
find qual clauses that enable merge and hash joins
293293
----make_one_rel()
294294
set_base_rel_pathlist()
295-
findscan and all index paths for each base relation
295+
findseqscan and all index paths for each base relation
296296
find selectivity of columns used in joins
297-
-----make_one_rel_by_joins()
298-
jump to geqo if needed
299-
else call make_rels_by_joins() for each level of join tree needed
300-
make_rels_by_joins():
297+
make_rel_from_joinlist()
298+
hand off join subproblems to a plugin, GEQO, or standard_join_search()
299+
-----standard_join_search()
300+
call join_search_one_level() for each level of join tree needed
301+
join_search_one_level():
301302
For each joinrel of the prior level, do make_rels_by_clause_joins()
302303
if it has join clauses, or make_rels_by_clauseless_joins() if not.
303304
Also generate "bushy plan" joins between joinrels of lower levels.
304-
Back atmake_one_rel_by_joins(), apply set_cheapest() to extract the
305+
Back atstandard_join_search(), apply set_cheapest() to extract the
305306
cheapest path for each newly constructed joinrel.
306307
Loop back if this wasn't the top join level.
307308
Back at query_planner:

‎src/backend/optimizer/path/allpaths.c‎

Lines changed: 29 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.164 2007/05/26 18:23:01 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.165 2007/09/26 18:51:50 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -37,6 +37,9 @@
3737
boolenable_geqo= false;/* just in case GUC doesn't set it */
3838
intgeqo_threshold;
3939

40+
/* Hook for plugins to replace standard_join_search() */
41+
join_search_hook_typejoin_search_hook=NULL;
42+
4043

4144
staticvoidset_base_rel_pathlists(PlannerInfo*root);
4245
staticvoidset_rel_pathlist(PlannerInfo*root,RelOptInfo*rel,
@@ -53,8 +56,6 @@ static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
5356
staticvoidset_values_pathlist(PlannerInfo*root,RelOptInfo*rel,
5457
RangeTblEntry*rte);
5558
staticRelOptInfo*make_rel_from_joinlist(PlannerInfo*root,List*joinlist);
56-
staticRelOptInfo*make_one_rel_by_joins(PlannerInfo*root,intlevels_needed,
57-
List*initial_rels);
5859
staticboolsubquery_is_pushdown_safe(Query*subquery,Query*topquery,
5960
bool*differentTypes);
6061
staticboolrecurse_pushdown_safe(Node*setOp,Query*topquery,
@@ -672,31 +673,48 @@ make_rel_from_joinlist(PlannerInfo *root, List *joinlist)
672673
{
673674
/*
674675
* Consider the different orders in which we could join the rels,
675-
* usingeitherGEQO or regularoptimizer.
676+
* usinga plugin,GEQO, ortheregularjoin search code.
676677
*/
677-
if (enable_geqo&&levels_needed >=geqo_threshold)
678+
if (join_search_hook)
679+
return (*join_search_hook) (root,levels_needed,initial_rels);
680+
elseif (enable_geqo&&levels_needed >=geqo_threshold)
678681
returngeqo(root,levels_needed,initial_rels);
679682
else
680-
returnmake_one_rel_by_joins(root,levels_needed,initial_rels);
683+
returnstandard_join_search(root,levels_needed,initial_rels);
681684
}
682685
}
683686

684687
/*
685-
*make_one_rel_by_joins
686-
* Findallpossible joinpaths for a query by successively finding ways
688+
*standard_join_search
689+
* Find possible joinpaths for a query by successively finding ways
687690
* to join component relations into join relations.
688691
*
689692
* 'levels_needed' is the number of iterations needed, ie, the number of
690693
*independent jointree items in the query. This is > 1.
691694
*
692695
* 'initial_rels' is a list of RelOptInfo nodes for each independent
693696
*jointree item.These are the components to be joined together.
697+
*Note that levels_needed == list_length(initial_rels).
694698
*
695699
* Returns the final level of join relations, i.e., the relation that is
696700
* the result of joining all the original relations together.
701+
* At least one implementation path must be provided for this relation and
702+
* all required sub-relations.
703+
*
704+
* To support loadable plugins that modify planner behavior by changing the
705+
* join searching algorithm, we provide a hook variable that lets a plugin
706+
* replace or supplement this function. Any such hook must return the same
707+
* final join relation as the standard code would, but it might have a
708+
* different set of implementation paths attached, and only the sub-joinrels
709+
* needed for these paths need have been instantiated.
710+
*
711+
* Note to plugin authors: the functions invoked during standard_join_search()
712+
* modify root->join_rel_list and root->join_rel_hash. If you want to do more
713+
* than one join-order search, you'll probably need to save and restore the
714+
* original states of those data structures. See geqo_eval() for an example.
697715
*/
698-
staticRelOptInfo*
699-
make_one_rel_by_joins(PlannerInfo*root,intlevels_needed,List*initial_rels)
716+
RelOptInfo*
717+
standard_join_search(PlannerInfo*root,intlevels_needed,List*initial_rels)
700718
{
701719
List**joinitems;
702720
intlev;
@@ -725,7 +743,7 @@ make_one_rel_by_joins(PlannerInfo *root, int levels_needed, List *initial_rels)
725743
* level, and build paths for making each one from every available
726744
* pair of lower-level relations.
727745
*/
728-
joinitems[lev]=make_rels_by_joins(root,lev,joinitems);
746+
joinitems[lev]=join_search_one_level(root,lev,joinitems);
729747

730748
/*
731749
* Do cleanup work on each just-processed rel.

‎src/backend/optimizer/path/joinrels.c‎

Lines changed: 7 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.86 2007/02/16 00:14:01 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.87 2007/09/26 18:51:50 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -29,18 +29,18 @@ static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel);
2929

3030

3131
/*
32-
*make_rels_by_joins
32+
*join_search_one_level
3333
* Consider ways to produce join relations containing exactly 'level'
3434
* jointree items. (This is one step of the dynamic-programming method
35-
* embodied inmake_one_rel_by_joins.) Join rel nodes for each feasible
35+
* embodied instandard_join_search.) Join rel nodes for each feasible
3636
* combination of lower-level rels are created and returned in a list.
3737
* Implementation paths are created for each such joinrel, too.
3838
*
3939
* level: level of rels we want to make this time.
4040
* joinrels[j], 1 <= j < level, is a list of rels containing j items.
4141
*/
4242
List*
43-
make_rels_by_joins(PlannerInfo*root,intlevel,List**joinrels)
43+
join_search_one_level(PlannerInfo*root,intlevel,List**joinrels)
4444
{
4545
List*result_rels=NIL;
4646
List*new_rels;
@@ -638,9 +638,9 @@ make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
638638
* Note: this is only a problem if one side of a degenerate outer join
639639
* contains multiple rels, or a clauseless join is required within an IN's
640640
* RHS; else we will find a join path via the "last ditch" case in
641-
*make_rels_by_joins(). We could dispense with this test if we were willing
642-
* to try bushy plans in the "last ditch" case, but that seems much less
643-
* efficient.
641+
*join_search_one_level(). We could dispense with this test if we were
642+
*willingto try bushy plans in the "last ditch" case, but that seems much
643+
*lessefficient.
644644
*/
645645
bool
646646
have_join_order_restriction(PlannerInfo*root,

‎src/include/optimizer/paths.h‎

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.98 2007/05/22 01:40:33 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.99 2007/09/26 18:51:51 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -23,7 +23,16 @@
2323
externboolenable_geqo;
2424
externintgeqo_threshold;
2525

26+
/* Hook for plugins to replace standard_join_search() */
27+
typedefRelOptInfo* (*join_search_hook_type) (PlannerInfo*root,
28+
intlevels_needed,
29+
List*initial_rels);
30+
externPGDLLIMPORTjoin_search_hook_typejoin_search_hook;
31+
32+
2633
externRelOptInfo*make_one_rel(PlannerInfo*root,List*joinlist);
34+
externRelOptInfo*standard_join_search(PlannerInfo*root,intlevels_needed,
35+
List*initial_rels);
2736

2837
#ifdefOPTIMIZER_DEBUG
2938
externvoiddebug_print_rel(PlannerInfo*root,RelOptInfo*rel);
@@ -89,7 +98,8 @@ extern void add_paths_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel,
8998
* joinrels.c
9099
* routines to determine which relations to join
91100
*/
92-
externList*make_rels_by_joins(PlannerInfo*root,intlevel,List**joinrels);
101+
externList*join_search_one_level(PlannerInfo*root,intlevel,
102+
List**joinrels);
93103
externRelOptInfo*make_join_rel(PlannerInfo*root,
94104
RelOptInfo*rel1,RelOptInfo*rel2);
95105
externboolhave_join_order_restriction(PlannerInfo*root,

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