granicus.if.org Git - postgresql/blob - src/backend/executor/tstoreReceiver.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * tstore_receiver.c
   4  *        an implementation of DestReceiver that stores the result tuples in
   5  *        a Tuplestore
   6  *
   7  *
   8  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
   9  * Portions Copyright (c) 1994, Regents of the University of California
  10  *
  11  * IDENTIFICATION
  12  *        $Header: /cvsroot/pgsql/src/backend/executor/tstoreReceiver.c,v 1.3 2003/05/02 20:54:34 tgl Exp $
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16
  17 #include "postgres.h"
  18
  19 #include "executor/tstoreReceiver.h"
  20 #include "utils/memutils.h"
  21 #include "utils/portal.h"
  22
  23 typedef struct
  24 {
  25         DestReceiver            pub;
  26         Tuplestorestate    *tstore;
  27         MemoryContext           cxt;
  28 } TStoreState;
  29
  30
  31 /*
  32  * Prepare to receive tuples from executor.
  33  *
  34  * XXX: As currently implemented, this routine is a hack: there should
  35  * be no tie between this code and the portal system. Instead, the
  36  * receiver function that is part of DestFunction should be passed a
  37  * QueryDesc, so that the call site of ExecutorRun can "sub-class"
  38  * QueryDesc and pass in any necessary addition information (in this
  39  * case, the Tuplestore to use).
  40  */
  41 static void
  42 tstoreSetupReceiver(DestReceiver *self, int operation,
  43                                         const char *portalname, TupleDesc typeinfo)
  44 {
  45         TStoreState *myState = (TStoreState *) self;
  46
  47         /* Should only be called within a suitably-prepped portal */
  48         if (CurrentPortal == NULL ||
  49                 CurrentPortal->holdStore == NULL)
  50                 elog(ERROR, "Tuplestore destination used in wrong context");
  51
  52         /* Debug check: make sure portal's result tuple desc is correct */
  53         Assert(CurrentPortal->tupDesc != NULL);
  54         Assert(equalTupleDescs(CurrentPortal->tupDesc, typeinfo));
  55
  56         myState->tstore = CurrentPortal->holdStore;
  57         myState->cxt = CurrentPortal->holdContext;
  58 }
  59
  60 /*
  61  * Receive a tuple from the executor and store it in the tuplestore.
  62  */
  63 static void
  64 tstoreReceiveTuple(HeapTuple tuple, TupleDesc typeinfo, DestReceiver *self)
  65 {
  66         TStoreState *myState = (TStoreState *) self;
  67         MemoryContext oldcxt = MemoryContextSwitchTo(myState->cxt);
  68
  69         tuplestore_puttuple(myState->tstore, tuple);
  70
  71         MemoryContextSwitchTo(oldcxt);
  72 }
  73
  74 /*
  75  * Clean up
  76  */
  77 static void
  78 tstoreCleanupReceiver(DestReceiver *self)
  79 {
  80         /* do nothing */
  81 }
  82
  83 /*
  84  * Initially create a DestReceiver object.
  85  */
  86 DestReceiver *
  87 tstoreReceiverCreateDR(void)
  88 {
  89         TStoreState *self = (TStoreState *) palloc(sizeof(TStoreState));
  90
  91         self->pub.receiveTuple = tstoreReceiveTuple;
  92         self->pub.setup = tstoreSetupReceiver;
  93         self->pub.cleanup = tstoreCleanupReceiver;
  94
  95         self->tstore = NULL;
  96         self->cxt = NULL;
  97
  98         return (DestReceiver *) self;
  99 }