Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commitba42002

Browse files
committed
Revise handling of dropped columns in JOIN alias lists to avoid a
performance problem pointed out by phil@vodafone: to wit, we werespending O(N^2) time to check dropped-ness in an N-deep join tree,even in the case where the tree was freshly constructed and couldn'tpossibly mention any dropped columns. Instead of recursing inget_rte_attribute_is_dropped(), change the data structure definition:the joinaliasvars list of a JOIN RTE must have a NULL Const insteadof a Var at any position that references a now-dropped column. Thiscosts nothing during normal parse-rewrite-plan path, and instead wehave a linear-time update to make when loading a stored rule thatmight contain now-dropped columns. While at it, move the responsibilityfor acquring locks on relations referenced by rules into this separatefunction (which I therefore chose to call AcquireRewriteLocks).This saves effort --- namely, duplicated lock grabs in parser and rewriter--- in the normal path at a cost of one extra non-locked heap_open()in the stored-rule path; seems a good tradeoff. A fringe benefit isthat it is now *much* clearer that we acquire lock on relations referencedin rules before we make any rewriter decisions based on their properties.(I don't know of any bug of that ilk, but it wasn't exactly clear before.)
1 parent7e209f6 commitba42002

File tree

12 files changed

+278
-90
lines changed

12 files changed

+278
-90
lines changed

‎src/backend/commands/explain.c

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1994-5, Regents of the University of California
88
*
99
* IDENTIFICATION
10-
* $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.135 2005/04/25 01:30:12 tgl Exp $
10+
* $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.136 2005/06/03 23:05:28 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -100,6 +100,12 @@ ExplainQuery(ExplainStmt *stmt, DestReceiver *dest)
100100
}
101101
else
102102
{
103+
/*
104+
* Must acquire locks in case we didn't come fresh from the parser.
105+
* XXX this also scribbles on query, another reason for copyObject
106+
*/
107+
AcquireRewriteLocks(query);
108+
103109
/* Rewrite through rule system */
104110
rewritten=QueryRewrite(query);
105111

@@ -166,6 +172,8 @@ ExplainOneQuery(Query *query, ExplainStmt *stmt, TupOutputState *tstate)
166172
cursorOptions=dcstmt->options;
167173
/* Still need to rewrite cursor command */
168174
Assert(query->commandType==CMD_SELECT);
175+
/* get locks (we assume ExplainQuery already copied tree) */
176+
AcquireRewriteLocks(query);
169177
rewritten=QueryRewrite(query);
170178
if (list_length(rewritten)!=1)
171179
elog(ERROR,"unexpected rewrite result");

‎src/backend/commands/portalcmds.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@
1414
*
1515
*
1616
* IDENTIFICATION
17-
* $PostgreSQL: pgsql/src/backend/commands/portalcmds.c,v 1.41 2005/04/28 21:47:11 tgl Exp $
17+
* $PostgreSQL: pgsql/src/backend/commands/portalcmds.c,v 1.42 2005/06/03 23:05:28 tgl Exp $
1818
*
1919
*-------------------------------------------------------------------------
2020
*/
@@ -76,6 +76,7 @@ PerformCursorOpen(DeclareCursorStmt *stmt, ParamListInfo params)
7676
* query, so we are not expecting rule rewriting to do anything
7777
* strange.
7878
*/
79+
AcquireRewriteLocks(query);
7980
rewritten=QueryRewrite(query);
8081
if (list_length(rewritten)!=1|| !IsA(linitial(rewritten),Query))
8182
elog(ERROR,"unexpected rewrite result");

‎src/backend/commands/prepare.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
* Copyright (c) 2002-2005, PostgreSQL Global Development Group
1111
*
1212
* IDENTIFICATION
13-
* $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.38 2005/05/29 04:23:03 tgl Exp $
13+
* $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.39 2005/06/0323:05:28 tgl Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -99,6 +99,7 @@ PrepareQuery(PrepareStmt *stmt)
9999
query=copyObject(stmt->query);
100100

101101
/* Rewrite the query. The result could be 0, 1, or many queries. */
102+
AcquireRewriteLocks(query);
102103
query_list=QueryRewrite(query);
103104

104105
/* Generate plans for queries.Snapshot is already set. */

‎src/backend/optimizer/util/var.c

Lines changed: 2 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.63 2004/12/31 22:00:23 pgsql Exp $
11+
* $PostgreSQL: pgsql/src/backend/optimizer/util/var.c,v 1.64 2005/06/03 23:05:28 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -524,9 +524,7 @@ flatten_join_alias_vars_mutator(Node *node,
524524
newvar= (Node*)lfirst(l);
525525
attnum++;
526526
/* Ignore dropped columns */
527-
if (get_rte_attribute_is_dropped(context->root->rtable,
528-
var->varno,
529-
attnum))
527+
if (IsA(newvar,Const))
530528
continue;
531529

532530
/*

‎src/backend/parser/parse_relation.c

Lines changed: 13 additions & 32 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.108 2005/05/29 17:10:23 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.109 2005/06/03 23:05:28 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1202,8 +1202,7 @@ addImplicitRTE(ParseState *pstate, RangeVar *relation)
12021202
* results. If include_dropped is TRUE then empty strings and NULL constants
12031203
* (not Vars!) are returned for dropped columns.
12041204
*
1205-
* The target RTE is the rtindex'th entry of rtable. (The whole rangetable
1206-
* must be passed since we need it to determine dropped-ness for JOIN columns.)
1205+
* The target RTE is the rtindex'th entry of rtable.
12071206
* sublevels_up is the varlevelsup value to use in the created Vars.
12081207
*
12091208
* The output lists go into *colnames and *colvars.
@@ -1358,33 +1357,28 @@ expandRTE(List *rtable, int rtindex, int sublevels_up,
13581357
varattno=0;
13591358
forboth(colname,rte->eref->colnames,aliasvar,rte->joinaliasvars)
13601359
{
1360+
Node*avar= (Node*)lfirst(aliasvar);
1361+
13611362
varattno++;
13621363

13631364
/*
13641365
* During ordinary parsing, there will never be any
13651366
* deleted columns in the join; but we have to check
13661367
* since this routine is also used by the rewriter,
13671368
* and joins found in stored rules might have join
1368-
* columns for since-deleted columns.
1369+
* columns for since-deleted columns. This will be
1370+
* signaled by a NULL Const in the alias-vars list.
13691371
*/
1370-
if (get_rte_attribute_is_dropped(rtable,rtindex,
1371-
varattno))
1372+
if (IsA(avar,Const))
13721373
{
13731374
if (include_dropped)
13741375
{
13751376
if (colnames)
13761377
*colnames=lappend(*colnames,
1377-
makeString(pstrdup("")));
1378+
makeString(pstrdup("")));
13781379
if (colvars)
1379-
{
1380-
/*
1381-
* can't use atttypid here, but it doesn't
1382-
* really matter what type the Const
1383-
* claims to be.
1384-
*/
13851380
*colvars=lappend(*colvars,
1386-
makeNullConst(INT4OID));
1387-
}
1381+
copyObject(avar));
13881382
}
13891383
continue;
13901384
}
@@ -1399,7 +1393,6 @@ expandRTE(List *rtable, int rtindex, int sublevels_up,
13991393

14001394
if (colvars)
14011395
{
1402-
Node*avar= (Node*)lfirst(aliasvar);
14031396
Var*varnode;
14041397

14051398
varnode=makeVar(rtindex,varattno,
@@ -1711,9 +1704,8 @@ get_rte_attribute_type(RangeTblEntry *rte, AttrNumber attnum,
17111704
*Check whether attempted attribute ref is to a dropped column
17121705
*/
17131706
bool
1714-
get_rte_attribute_is_dropped(List*rtable,intrtindex,AttrNumberattnum)
1707+
get_rte_attribute_is_dropped(RangeTblEntry*rte,AttrNumberattnum)
17151708
{
1716-
RangeTblEntry*rte=rt_fetch(rtindex,rtable);
17171709
boolresult;
17181710

17191711
switch (rte->rtekind)
@@ -1750,8 +1742,8 @@ get_rte_attribute_is_dropped(List *rtable, int rtindex, AttrNumber attnum)
17501742
* constructed, but one in a stored rule might contain
17511743
* columns that were dropped from the underlying tables,
17521744
* if said columns are nowhere explicitly referenced in
1753-
* the rule.So we havetorecursively look at the
1754-
*referenced column.
1745+
* the rule.This will be signaledtous by a NULL Const
1746+
*in the joinaliasvars list.
17551747
*/
17561748
Var*aliasvar;
17571749

@@ -1760,18 +1752,7 @@ get_rte_attribute_is_dropped(List *rtable, int rtindex, AttrNumber attnum)
17601752
elog(ERROR,"invalid varattno %d",attnum);
17611753
aliasvar= (Var*)list_nth(rte->joinaliasvars,attnum-1);
17621754

1763-
/*
1764-
* If the list item isn't a simple Var, then it must
1765-
* represent a merged column, ie a USING column, and so it
1766-
* couldn't possibly be dropped (since it's referenced in
1767-
* the join clause).
1768-
*/
1769-
if (!IsA(aliasvar,Var))
1770-
result= false;
1771-
else
1772-
result=get_rte_attribute_is_dropped(rtable,
1773-
aliasvar->varno,
1774-
aliasvar->varattno);
1755+
result=IsA(aliasvar,Const);
17751756
}
17761757
break;
17771758
caseRTE_FUNCTION:

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp