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/*-------------------------------------------------------------------------
*
* portal.h
* POSTGRES portal definitions.
*
* A portal is an abstraction which represents the execution state of
* a running query (specifically, a CURSOR).
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: portal.h,v 1.40 2003/03/27 16:51:29 momjian Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef PORTAL_H
#define PORTAL_H
#include "executor/execdesc.h"
#include "nodes/memnodes.h"
#include "utils/tuplestore.h"
/*
* We support three kinds of scroll behavior:
*
* (1) Neither NO SCROLL nor SCROLL was specified: to remain backward
* compatible, we allow backward fetches here, unless it would
* impose additional runtime overhead to do so.
*
* (2) NO SCROLL was specified: don't allow any backward fetches.
*
* (3) SCROLL was specified: allow all kinds of backward fetches, even
* if we need to take a slight performance hit to do so.
*
* Case #1 is converted to #2 or #3 by looking at the query itself and
* determining if scrollability can be supported without additional
* overhead.
*/
typedef enum
{
DEFAULT_SCROLL,
DISABLE_SCROLL,
ENABLE_SCROLL
} ScrollType;
typedef struct PortalData *Portal;
typedef struct PortalData
{
char *name; /* Portal's name */
MemoryContext heap; /* memory for storing short-term data */
QueryDesc *queryDesc; /* Info about query associated with portal */
void (*cleanup) (Portal); /* Cleanup routine (optional) */
ScrollType scrollType; /* Allow backward fetches? */
bool holdOpen; /* hold open after txn ends? */
TransactionId createXact; /* the xid of the creating txn */
Tuplestorestate *holdStore; /* store for holdable cursors */
MemoryContext holdContext; /* memory for long-term data */
/*
* atStart, atEnd and portalPos indicate the current cursor position.
* portalPos is zero before the first row, N after fetching N'th row of
* query. After we run off the end, portalPos = # of rows in query, and
* atEnd is true. If portalPos overflows, set posOverflow (this causes
* us to stop relying on its value for navigation). Note that atStart
* implies portalPos == 0, but not the reverse (portalPos could have
* overflowed).
*/
bool atStart;
bool atEnd;
bool posOverflow;
long portalPos;
} PortalData;
/*
* PortalIsValid
* True iff portal is valid.
*/
#define PortalIsValid(p) PointerIsValid(p)
/*
* Access macros for Portal ... use these in preference to field access.
*/
#define PortalGetQueryDesc(portal) ((portal)->queryDesc)
#define PortalGetHeapMemory(portal) ((portal)->heap)
extern void EnablePortalManager(void);
extern void AtEOXact_portals(bool isCommit);
extern Portal CreatePortal(const char *name);
extern void PortalDrop(Portal portal, bool persistHoldable);
extern Portal GetPortalByName(const char *name);
extern void PortalSetQuery(Portal portal, QueryDesc *queryDesc,
void (*cleanup) (Portal portal));
extern void PersistHoldablePortal(Portal portal);
#endif /* PORTAL_H */
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