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when user does another FETCH after reaching end of data, or another FETCH backwards after reaching start. This is needed because some plan nodes are not very robust about being called again after they've already returned NULL; for example, MergeJoin will crash in some states but not others. While the ideal approach would be for them all to handle this correctly, it seems foolish to assume that no such bugs would creep in again once cleaned up. Therefore, the most robust answer is to prevent the situation from arising at all.
72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
/*-------------------------------------------------------------------------
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*
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* portal.h
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* POSTGRES portal definitions.
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*
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*
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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $Id: portal.h,v 1.26 2001/02/27 22:07:34 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* Note:
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* A portal is an abstraction which represents the execution state of
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* a running query (specifically, a CURSOR).
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*/
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#ifndef PORTAL_H
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#define PORTAL_H
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#include "executor/execdesc.h"
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#include "nodes/memnodes.h"
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typedef struct PortalData *Portal;
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typedef struct PortalData
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{
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char *name; /* Portal's name */
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MemoryContext heap; /* subsidiary memory */
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QueryDesc *queryDesc; /* Info about query associated with portal */
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TupleDesc attinfo;
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EState *state; /* Execution state of query */
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bool atStart; /* T => fetch backwards is not allowed */
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bool atEnd; /* T => fetch forwards is not allowed */
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void (*cleanup) (Portal); /* Cleanup routine (optional) */
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} PortalData;
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/*
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* PortalIsValid
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* True iff portal is valid.
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*/
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#define PortalIsValid(p) PointerIsValid(p)
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/*
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* Access macros for Portal ... use these in preference to field access.
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*/
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#define PortalGetQueryDesc(portal) ((portal)->queryDesc)
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#define PortalGetTupleDesc(portal) ((portal)->attinfo)
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#define PortalGetState(portal) ((portal)->state)
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#define PortalGetHeapMemory(portal) ((portal)->heap)
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/*
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* estimate of the maximum number of open portals a user would have,
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* used in initially sizing the PortalHashTable in EnablePortalManager()
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*/
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#define PORTALS_PER_USER 10
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extern void EnablePortalManager(void);
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extern void AtEOXact_portals(void);
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extern Portal CreatePortal(char *name);
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extern void PortalDrop(Portal *portalP);
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extern Portal GetPortalByName(char *name);
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extern void PortalSetQuery(Portal portal, QueryDesc *queryDesc,
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TupleDesc attinfo, EState *state,
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void (*cleanup) (Portal portal));
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#endif /* PORTAL_H */
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