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Commitc139317

Browse files
committed
Avoid redundant relation lock grabs during planning, and make sure
that we acquire a lock on relations added to the query due to inheritance.Formerly, no such lock was held throughout planning, which meant thata schema change could occur to invalidate the plan before it's evenbeen completed.
1 parent353f111 commitc139317

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3 files changed

+40
-21
lines changed

3 files changed

+40
-21
lines changed

‎src/backend/optimizer/prep/preptlist.c

Lines changed: 6 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@
1515
* Portions Copyright (c) 1994, Regents of the University of California
1616
*
1717
* IDENTIFICATION
18-
* $PostgreSQL: pgsql/src/backend/optimizer/prep/preptlist.c,v 1.75 2005/04/28 21:47:14 tgl Exp $
18+
* $PostgreSQL: pgsql/src/backend/optimizer/prep/preptlist.c,v 1.76 2005/05/23 03:01:13 tgl Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
@@ -189,9 +189,11 @@ expand_targetlist(List *tlist, int command_type,
189189
* attributes.
190190
*
191191
* Scan the tuple description in the relation's relcache entry to make
192-
* sure we have all the user attributes in the right order.
192+
* sure we have all the user attributes in the right order. We assume
193+
* that the rewriter already acquired at least AccessShareLock on the
194+
* relation, so we need no lock here.
193195
*/
194-
rel=heap_open(getrelid(result_relation,range_table),AccessShareLock);
196+
rel=heap_open(getrelid(result_relation,range_table),NoLock);
195197

196198
numattrs=RelationGetNumberOfAttributes(rel);
197199

@@ -326,7 +328,7 @@ expand_targetlist(List *tlist, int command_type,
326328
tlist_item=lnext(tlist_item);
327329
}
328330

329-
heap_close(rel,AccessShareLock);
331+
heap_close(rel,NoLock);
330332

331333
returnnew_tlist;
332334
}

‎src/backend/optimizer/util/plancat.c

Lines changed: 25 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,7 @@
99
*
1010
*
1111
* IDENTIFICATION
12-
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.107 2005/05/22 22:30:20 tgl Exp $
12+
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.108 2005/05/23 03:01:14 tgl Exp $
1313
*
1414
*-------------------------------------------------------------------------
1515
*/
@@ -67,7 +67,25 @@ get_relation_info(Oid relationObjectId, RelOptInfo *rel)
6767
boolhasindex;
6868
List*indexinfos=NIL;
6969

70-
relation=heap_open(relationObjectId,AccessShareLock);
70+
/*
71+
* Normally, we can assume the rewriter already acquired at least
72+
* AccessShareLock on each relation used in the query. However this
73+
* will not be the case for relations added to the query because they
74+
* are inheritance children of some relation mentioned explicitly.
75+
* For them, this is the first access during the parse/rewrite/plan
76+
* pipeline, and so we need to obtain and keep a suitable lock.
77+
*
78+
* XXX really, a suitable lock is RowShareLock if the relation is
79+
* an UPDATE/DELETE target, and AccessShareLock otherwise. However
80+
* we cannot easily tell here which to get, so for the moment just
81+
* get AccessShareLock always. The executor will get the right lock
82+
* when it runs, which means there is a very small chance of deadlock
83+
* trying to upgrade our lock.
84+
*/
85+
if (rel->reloptkind==RELOPT_BASEREL)
86+
relation=heap_open(relationObjectId,NoLock);
87+
else
88+
relation=heap_open(relationObjectId,AccessShareLock);
7189

7290
rel->min_attr=FirstLowInvalidHeapAttributeNumber+1;
7391
rel->max_attr=RelationGetNumberOfAttributes(relation);
@@ -205,8 +223,8 @@ get_relation_info(Oid relationObjectId, RelOptInfo *rel)
205223

206224
rel->indexlist=indexinfos;
207225

208-
/*XXX keep thelockhere? */
209-
heap_close(relation,AccessShareLock);
226+
/*close rel, but keeplockif any */
227+
heap_close(relation,NoLock);
210228
}
211229

212230
/*
@@ -374,7 +392,8 @@ build_physical_tlist(Query *root, RelOptInfo *rel)
374392
switch (rte->rtekind)
375393
{
376394
caseRTE_RELATION:
377-
relation=heap_open(rte->relid,AccessShareLock);
395+
/* Assume we already have adequate lock */
396+
relation=heap_open(rte->relid,NoLock);
378397

379398
numattrs=RelationGetNumberOfAttributes(relation);
380399
for (attrno=1;attrno <=numattrs;attrno++)
@@ -401,7 +420,7 @@ build_physical_tlist(Query *root, RelOptInfo *rel)
401420
false));
402421
}
403422

404-
heap_close(relation,AccessShareLock);
423+
heap_close(relation,NoLock);
405424
break;
406425

407426
caseRTE_SUBQUERY:

‎src/backend/optimizer/util/relnode.c

Lines changed: 9 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/util/relnode.c,v 1.65 2005/04/22 21:58:31 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/util/relnode.c,v 1.66 2005/05/23 03:01:14 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -23,7 +23,8 @@
2323
#include"parser/parsetree.h"
2424

2525

26-
staticRelOptInfo*make_base_rel(Query*root,intrelid);
26+
staticRelOptInfo*make_reloptinfo(Query*root,intrelid,
27+
RelOptKindreloptkind);
2728
staticvoidbuild_joinrel_tlist(Query*root,RelOptInfo*joinrel);
2829
staticList*build_joinrel_restrictlist(Query*root,
2930
RelOptInfo*joinrel,
@@ -67,7 +68,7 @@ build_base_rel(Query *root, int relid)
6768
}
6869

6970
/* No existing RelOptInfo for this base rel, so make a new one */
70-
rel=make_base_rel(root,relid);
71+
rel=make_reloptinfo(root,relid,RELOPT_BASEREL);
7172

7273
/* and add it to the list */
7374
root->base_rel_list=lcons(rel,root->base_rel_list);
@@ -102,11 +103,8 @@ build_other_rel(Query *root, int relid)
102103
}
103104

104105
/* No existing RelOptInfo for this other rel, so make a new one */
105-
rel=make_base_rel(root,relid);
106-
107106
/* presently, must be an inheritance child rel */
108-
Assert(rel->reloptkind==RELOPT_BASEREL);
109-
rel->reloptkind=RELOPT_OTHER_CHILD_REL;
107+
rel=make_reloptinfo(root,relid,RELOPT_OTHER_CHILD_REL);
110108

111109
/* and add it to the list */
112110
root->other_rel_list=lcons(rel,root->other_rel_list);
@@ -115,18 +113,18 @@ build_other_rel(Query *root, int relid)
115113
}
116114

117115
/*
118-
*make_base_rel
119-
* Construct abase-relationRelOptInfo for the specified rangetable index.
116+
*make_reloptinfo
117+
* Construct a RelOptInfo for the specified rangetable index.
120118
*
121119
* Common code for build_base_rel and build_other_rel.
122120
*/
123121
staticRelOptInfo*
124-
make_base_rel(Query*root,intrelid)
122+
make_reloptinfo(Query*root,intrelid,RelOptKindreloptkind)
125123
{
126124
RelOptInfo*rel=makeNode(RelOptInfo);
127125
RangeTblEntry*rte=rt_fetch(relid,root->rtable);
128126

129-
rel->reloptkind=RELOPT_BASEREL;
127+
rel->reloptkind=reloptkind;
130128
rel->relids=bms_make_singleton(relid);
131129
rel->rows=0;
132130
rel->width=0;

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