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Commit6fdc44b

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Tweak querytree-dependency-extraction code so that columns of tables
that are explicitly JOINed are not considered dependencies unless theyare actually used in the query: mere presence in the joinaliasvarslist of a JOIN RTE doesn't count as being used. The patch touchesa number of files because I needed to generalize the API ofquery_tree_walker to support an additional flag bit, but the changesare otherwise quite small.
1 parentd634a59 commit6fdc44b

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8 files changed

+89
-55
lines changed

8 files changed

+89
-55
lines changed

‎src/backend/catalog/dependency.c

Lines changed: 25 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.9 2002/09/04 20:31:13 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/catalog/dependency.c,v 1.10 2002/09/11 14:48:54 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -684,6 +684,12 @@ recordDependencyOnExpr(const ObjectAddress *depender,
684684

685685
/*
686686
* Recursively search an expression tree for object references.
687+
*
688+
* Note: we avoid creating references to columns of tables that participate
689+
* in an SQL JOIN construct, but are not actually used anywhere in the query.
690+
* To do so, we do not scan the joinaliasvars list of a join RTE while
691+
* scanning the query rangetable, but instead scan each individual entry
692+
* of the alias list when we find a reference to it.
687693
*/
688694
staticbool
689695
find_expr_references_walker(Node*node,
@@ -716,10 +722,24 @@ find_expr_references_walker(Node *node,
716722
elog(ERROR,"find_expr_references_walker: bogus varno %d",
717723
var->varno);
718724
rte=rt_fetch(var->varno,rtable);
719-
/* If it's a plain relation, reference this column */
720725
if (rte->rtekind==RTE_RELATION)
726+
{
727+
/* If it's a plain relation, reference this column */
728+
/* NB: this code works for whole-row Var with attno 0, too */
721729
add_object_address(OCLASS_CLASS,rte->relid,var->varattno,
722730
&context->addrs);
731+
}
732+
elseif (rte->rtekind==RTE_JOIN)
733+
{
734+
/* Scan join output column to add references to join inputs */
735+
if (var->varattno <=0||
736+
var->varattno>length(rte->joinaliasvars))
737+
elog(ERROR,"find_expr_references_walker: bogus varattno %d",
738+
var->varattno);
739+
find_expr_references_walker((Node*)nth(var->varattno-1,
740+
rte->joinaliasvars),
741+
context);
742+
}
723743
return false;
724744
}
725745
if (IsA(node,Expr))
@@ -766,7 +786,7 @@ find_expr_references_walker(Node *node,
766786
* Add whole-relation refs for each plain relation mentioned in
767787
* the subquery's rtable. (Note: query_tree_walker takes care of
768788
* recursing into RTE_FUNCTION and RTE_SUBQUERY RTEs, so no need
769-
* to do that here.)
789+
* to do that here. But keep it from looking at join alias lists.)
770790
*/
771791
foreach(rtable,query->rtable)
772792
{
@@ -781,7 +801,8 @@ find_expr_references_walker(Node *node,
781801
context->rtables=lcons(query->rtable,context->rtables);
782802
result=query_tree_walker(query,
783803
find_expr_references_walker,
784-
(void*)context, true);
804+
(void*)context,
805+
QTW_IGNORE_JOINALIASES);
785806
context->rtables=lnext(context->rtables);
786807
returnresult;
787808
}

‎src/backend/optimizer/prep/prepunion.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@
1414
*
1515
*
1616
* IDENTIFICATION
17-
* $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.78 2002/09/04 20:31:22 momjian Exp $
17+
* $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.79 2002/09/11 14:48:55 tgl Exp $
1818
*
1919
*-------------------------------------------------------------------------
2020
*/
@@ -774,7 +774,7 @@ adjust_inherited_attrs(Node *node,
774774
if (newnode->resultRelation==old_rt_index)
775775
newnode->resultRelation=new_rt_index;
776776
query_tree_mutator(newnode,adjust_inherited_attrs_mutator,
777-
(void*)&context,false);
777+
(void*)&context,QTW_IGNORE_SUBQUERIES);
778778
return (Node*)newnode;
779779
}
780780
else

‎src/backend/optimizer/util/clauses.c

Lines changed: 25 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.108 2002/09/04 20:31:22 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.109 2002/09/11 14:48:54 tgl Exp $
1212
*
1313
* HISTORY
1414
* AUTHORDATEMAJOR EVENT
@@ -1788,7 +1788,7 @@ simplify_op_or_func(Expr *expr, List *args)
17881788
*{
17891789
*adjust context for subquery;
17901790
*result = query_tree_walker((Query *) node, my_walker, context,
1791-
*true); // to visitsubquery RTEs too
1791+
*0); // to visitrtable items too
17921792
*restore context if needed;
17931793
*return result;
17941794
*}
@@ -1994,16 +1994,17 @@ expression_tree_walker(Node *node,
19941994
* walker intends to descend into subqueries. It is also useful for
19951995
* descending into subqueries within a walker.
19961996
*
1997-
* If visitQueryRTEs is true, the walker will also be called on sub-Query
1998-
* nodes present in subquery rangetable entries of the given Query. This
1999-
* is optional since some callers handle those sub-queries separately,
2000-
* or don't really want to see subqueries anyway.
1997+
* Some callers want to suppress visitation of certain items in the sub-Query,
1998+
* typically because they need to process them specially, or don't actually
1999+
* want to recurse into subqueries. This is supported by the flags argument,
2000+
* which is the bitwise OR of flag values to suppress visitation of
2001+
* indicated items. (More flag bits may be added as needed.)
20012002
*/
20022003
bool
20032004
query_tree_walker(Query*query,
20042005
bool (*walker) (),
20052006
void*context,
2006-
boolvisitQueryRTEs)
2007+
intflags)
20072008
{
20082009
List*rt;
20092010

@@ -2028,13 +2029,14 @@ query_tree_walker(Query *query,
20282029
/* nothing to do */
20292030
break;
20302031
caseRTE_SUBQUERY:
2031-
if (visitQueryRTEs)
2032+
if (! (flags&QTW_IGNORE_SUBQUERIES))
20322033
if (walker(rte->subquery,context))
20332034
return true;
20342035
break;
20352036
caseRTE_JOIN:
2036-
if (walker(rte->joinaliasvars,context))
2037-
return true;
2037+
if (! (flags&QTW_IGNORE_JOINALIASES))
2038+
if (walker(rte->joinaliasvars,context))
2039+
return true;
20382040
break;
20392041
caseRTE_FUNCTION:
20402042
if (walker(rte->funcexpr,context))
@@ -2388,16 +2390,17 @@ expression_tree_mutator(Node *node,
23882390
* if you don't want to change the original. All substructure is safely
23892391
* copied, however.
23902392
*
2391-
* If visitQueryRTEs is true, the mutator will also be called on sub-Query
2392-
* nodes present in subquery rangetable entries of the given Query. This
2393-
* is optional since some callers handle those sub-queries separately,
2394-
* or don't really want to see subqueries anyway.
2393+
* Some callers want to suppress mutating of certain items in the sub-Query,
2394+
* typically because they need to process them specially, or don't actually
2395+
* want to recurse into subqueries. This is supported by the flags argument,
2396+
* which is the bitwise OR of flag values to suppress mutating of
2397+
* indicated items. (More flag bits may be added as needed.)
23952398
*/
23962399
void
23972400
query_tree_mutator(Query*query,
23982401
Node*(*mutator) (),
23992402
void*context,
2400-
boolvisitQueryRTEs)
2403+
intflags)
24012404
{
24022405
List*newrt=NIL;
24032406
List*rt;
@@ -2420,7 +2423,7 @@ query_tree_mutator(Query *query,
24202423
/* nothing to do, don't bother to make a copy */
24212424
break;
24222425
caseRTE_SUBQUERY:
2423-
if (visitQueryRTEs)
2426+
if (! (flags&QTW_IGNORE_SUBQUERIES))
24242427
{
24252428
FLATCOPY(newrte,rte,RangeTblEntry);
24262429
CHECKFLATCOPY(newrte->subquery,rte->subquery,Query);
@@ -2429,9 +2432,12 @@ query_tree_mutator(Query *query,
24292432
}
24302433
break;
24312434
caseRTE_JOIN:
2432-
FLATCOPY(newrte,rte,RangeTblEntry);
2433-
MUTATE(newrte->joinaliasvars,rte->joinaliasvars,List*);
2434-
rte=newrte;
2435+
if (! (flags&QTW_IGNORE_JOINALIASES))
2436+
{
2437+
FLATCOPY(newrte,rte,RangeTblEntry);
2438+
MUTATE(newrte->joinaliasvars,rte->joinaliasvars,List*);
2439+
rte=newrte;
2440+
}
24352441
break;
24362442
caseRTE_FUNCTION:
24372443
FLATCOPY(newrte,rte,RangeTblEntry);

‎src/backend/optimizer/util/var.c

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/var.c,v 1.39 2002/09/04 20:31:22 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/optimizer/util/var.c,v 1.40 2002/09/11 14:48:54 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -82,7 +82,7 @@ pull_varnos(Node *node)
8282
*/
8383
if (node&&IsA(node,Query))
8484
query_tree_walker((Query*)node,pull_varnos_walker,
85-
(void*)&context,true);
85+
(void*)&context,0);
8686
else
8787
pull_varnos_walker(node,&context);
8888

@@ -128,7 +128,7 @@ pull_varnos_walker(Node *node, pull_varnos_context *context)
128128

129129
context->sublevels_up++;
130130
result=query_tree_walker((Query*)node,pull_varnos_walker,
131-
(void*)context,true);
131+
(void*)context,0);
132132
context->sublevels_up--;
133133
returnresult;
134134
}
@@ -165,7 +165,7 @@ contain_var_reference(Node *node, int varno, int varattno, int levelsup)
165165
if (node&&IsA(node,Query))
166166
returnquery_tree_walker((Query*)node,
167167
contain_var_reference_walker,
168-
(void*)&context,true);
168+
(void*)&context,0);
169169
else
170170
returncontain_var_reference_walker(node,&context);
171171
}
@@ -212,7 +212,7 @@ contain_var_reference_walker(Node *node,
212212
context->sublevels_up++;
213213
result=query_tree_walker((Query*)node,
214214
contain_var_reference_walker,
215-
(void*)context,true);
215+
(void*)context,0);
216216
context->sublevels_up--;
217217
returnresult;
218218
}

‎src/backend/rewrite/rewriteDefine.c

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteDefine.c,v 1.79 2002/09/04 20:31:25 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteDefine.c,v 1.80 2002/09/11 14:48:54 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -464,9 +464,10 @@ setRuleCheckAsUser(Query *qry, Oid userid)
464464
}
465465

466466
/* If there are sublinks, search for them and process their RTEs */
467+
/* ignore subqueries in rtable because we already processed them */
467468
if (qry->hasSubLinks)
468469
query_tree_walker(qry,setRuleCheckAsUser_walker, (void*)&userid,
469-
false/* already did the ones in rtable */);
470+
QTW_IGNORE_SUBQUERIES);
470471
}
471472

472473
/*

‎src/backend/rewrite/rewriteHandler.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.108 2002/09/04 20:31:25 momjian Exp $
10+
* $Header: /cvsroot/pgsql/src/backend/rewrite/rewriteHandler.c,v 1.109 2002/09/11 14:48:54 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -822,11 +822,12 @@ fireRIRrules(Query *parsetree)
822822
}
823823

824824
/*
825-
* Recurse into sublink subqueries, too.
825+
* Recurse into sublink subqueries, too. But we already did the ones
826+
* in the rtable.
826827
*/
827828
if (parsetree->hasSubLinks)
828829
query_tree_walker(parsetree,fireRIRonSubLink,NULL,
829-
false/* already handled the ones in rtable */);
830+
QTW_IGNORE_SUBQUERIES);
830831

831832
/*
832833
* If the query was marked having aggregates, check if this is still

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