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Fix EXPLAIN ANALYZE bug noted by Wiebe Cazemier: although we were

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properly advancing the CommandCounter between multiple sub-queries
generated by rules, we forgot to update the snapshot being used, so
that the successive sub-queries didn't actually see each others'
results.  This is still not *exactly* like the semantics of normal
execution of the same queries, in that we don't take new transaction
snapshots and hence don't see changes from concurrently committed
commands, but I think that's OK and probably even preferable for
EXPLAIN ANALYZE.
This commit is contained in:
Tom Lane 2005-10-21 16:43:33 +00:00
parent ef3b7cd328
commit 9fc24f2bf6
2 changed files with 20 additions and 2 deletions
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11
src/backend/commands/explain.c
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1994-5, Regents of the University of California * Portions Copyright (c) 1994-5, Regents of the University of California
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.138 2005/10/15 02:49:15 momjian Exp $ * $PostgreSQL: pgsql/src/backend/commands/explain.c,v 1.139 2005/10/21 16:43:33 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -196,6 +196,15 @@ ExplainOneQuery(Query *query, ExplainStmt *stmt, TupOutputState *tstate)
/* plan the query */ /* plan the query */
plan = planner(query, isCursor, cursorOptions, NULL); plan = planner(query, isCursor, cursorOptions, NULL);
/*
* Update snapshot command ID to ensure this query sees results of any
* previously executed queries. (It's a bit cheesy to modify
* ActiveSnapshot without making a copy, but for the limited ways in
* which EXPLAIN can be invoked, I think it's OK, because the active
* snapshot shouldn't be shared with anything else anyway.)
*/
ActiveSnapshot->curcid = GetCurrentCommandId();
/* Create a QueryDesc requesting no output */ /* Create a QueryDesc requesting no output */
queryDesc = CreateQueryDesc(query, plan, queryDesc = CreateQueryDesc(query, plan,
ActiveSnapshot, InvalidSnapshot, ActiveSnapshot, InvalidSnapshot,

11
src/backend/commands/prepare.c
View File

@ -10,7 +10,7 @@
* Copyright (c) 2002-2005, PostgreSQL Global Development Group * Copyright (c) 2002-2005, PostgreSQL Global Development Group
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.41 2005/10/15 02:49:15 momjian Exp $ * $PostgreSQL: pgsql/src/backend/commands/prepare.c,v 1.42 2005/10/21 16:43:33 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -605,6 +605,15 @@ ExplainExecuteQuery(ExplainStmt *stmt, TupOutputState *tstate)
query->into = execstmt->into; query->into = execstmt->into;
} }
/*
* Update snapshot command ID to ensure this query sees results of
* any previously executed queries. (It's a bit cheesy to modify
* ActiveSnapshot without making a copy, but for the limited ways
* in which EXPLAIN can be invoked, I think it's OK, because the
* active snapshot shouldn't be shared with anything else anyway.)
*/
ActiveSnapshot->curcid = GetCurrentCommandId();
/* Create a QueryDesc requesting no output */ /* Create a QueryDesc requesting no output */
qdesc = CreateQueryDesc(query, plan, qdesc = CreateQueryDesc(query, plan,
ActiveSnapshot, InvalidSnapshot, ActiveSnapshot, InvalidSnapshot,