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Revert my bad decision of about a year ago to make PortalDefineQuery

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responsible for copying the query string into the new Portal.  Such copying
is unnecessary in the common code path through exec_simple_query, and in
this case it can be enormously expensive because the string might contain
a large number of individual commands; we were copying the entire, long
string for each command, resulting in O(N^2) behavior for N commands.
(This is the cause of bug #4079.)  A second problem with it is that
PortalDefineQuery really can't risk error, because if it elog's before
having set up the Portal, we will leak the plancache refcount that the
caller is trying to hand off to the portal.  So go back to the design in
which the caller is responsible for making sure everything is copied into
the portal if necessary.
This commit is contained in:
Tom Lane
2008-04-02 18:31:50 +00:00
parent ad6bf716ba
commit 1591fcbec7
5 changed files with 73 additions and 24 deletions
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20
src/backend/utils/mmgr/portalmem.c
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@@ -12,7 +12,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.108 2008/03/25 22:42:45 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/mmgr/portalmem.c,v 1.109 2008/04/02 18:31:50 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -274,9 +274,7 @@ CreateNewPortal(void)
*
* Notes: commandTag shall be NULL if and only if the original query string
* (before rewriting) was an empty string. Also, the passed commandTag must
* be a pointer to a constant string, since it is not copied. However,
* prepStmtName and sourceText, if provided, are copied into the portal's
* heap context for safekeeping.
* be a pointer to a constant string, since it is not copied.
*
* If cplan is provided, then it is a cached plan containing the stmts,
* and the caller must have done RevalidateCachedPlan(), causing a refcount
@@ -285,6 +283,14 @@ CreateNewPortal(void)
* If cplan is NULL, then it is the caller's responsibility to ensure that
* the passed plan trees have adequate lifetime. Typically this is done by
* copying them into the portal's heap context.
*
* The caller is also responsible for ensuring that the passed prepStmtName
* and sourceText (if not NULL) have adequate lifetime.
*
* NB: this function mustn't do much beyond storing the passed values; in
* particular don't do anything that risks elog(ERROR). If that were to
* happen here before storing the cplan reference, we'd leak the plancache
* refcount that the caller is trying to hand off to us.
*/
void
PortalDefineQuery(Portal portal,
@@ -299,10 +305,8 @@ PortalDefineQuery(Portal portal,
Assert(commandTag != NULL || stmts == NIL);
portal->prepStmtName = prepStmtName ?
MemoryContextStrdup(PortalGetHeapMemory(portal), prepStmtName) : NULL;
portal->sourceText = sourceText ?
MemoryContextStrdup(PortalGetHeapMemory(portal), sourceText) : NULL;
portal->prepStmtName = prepStmtName;
portal->sourceText = sourceText;
portal->commandTag = commandTag;
portal->stmts = stmts;
portal->cplan = cplan;