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Restructure parsetree representation of DECLARE CURSOR: now it's a

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utility statement (DeclareCursorStmt) with a SELECT query dangling from
it, rather than a SELECT query with a few unusual fields in it.  Add
code to determine whether a planned query can safely be run backwards.
If DECLARE CURSOR specifies SCROLL, ensure that the plan can be run
backwards by adding a Materialize plan node if it can't.  Without SCROLL,
you get an error if you try to fetch backwards from a cursor that can't
handle it.  (There is still some discussion about what the exact
behavior should be, but this is necessary infrastructure in any case.)
Along the way, make EXPLAIN DECLARE CURSOR work.
This commit is contained in:
Tom Lane
2003-03-10 03:53:52 +00:00
parent b9e8ffcd5d
commit aa83bc04e0
40 changed files with 664 additions and 574 deletions
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17
src/backend/utils/mmgr/portalmem.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.51 2002/12/30 22:10:54 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.52 2003/03/10 03:53:51 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -33,16 +33,25 @@
#include "postgres.h"
#include "executor/executor.h"
#include "utils/hsearch.h"
#include "utils/memutils.h"
#include "utils/portal.h"
/*
* estimate of the maximum number of open portals a user would have,
* used in initially sizing the PortalHashTable in EnablePortalManager()
*/
#define PORTALS_PER_USER 64
/* ----------------
* Global state
* ----------------
*/
#define MAX_PORTALNAME_LEN 64
#define MAX_PORTALNAME_LEN NAMEDATALEN
typedef struct portalhashent
{
@@ -158,7 +167,8 @@ PortalSetQuery(Portal portal,
AssertArg(PortalIsValid(portal));
portal->queryDesc = queryDesc;
portal->atStart = true; /* Allow fetch forward only */
portal->backwardOK = ExecSupportsBackwardScan(queryDesc->plantree);
portal->atStart = true; /* Allow fetch forward only, to start */
portal->atEnd = false;
portal->cleanup = cleanup;
}
@@ -201,6 +211,7 @@ CreatePortal(const char *name)
/* initialize portal query */
portal->queryDesc = NULL;
portal->backwardOK = false;
portal->atStart = true; /* disallow fetches until query is set */
portal->atEnd = true;
portal->cleanup = NULL;