src/backend/executor/tstoreReceiver.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * tstoreReceiver.c
   4  *        an implementation of DestReceiver that stores the result tuples in
   5  *        a Tuplestore
   6  *
   7  *
   8  * Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
   9  * Portions Copyright (c) 1994, Regents of the University of California
  10  *
  11  * IDENTIFICATION
  12  *        $PostgreSQL: pgsql/src/backend/executor/tstoreReceiver.c,v 1.18 2007/01/05 22:19:29 momjian Exp $
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16
  17 #include "postgres.h"
  18
  19 #include "executor/tstoreReceiver.h"
  20
  21
  22 typedef struct
  23 {
  24         DestReceiver pub;
  25         Tuplestorestate *tstore;
  26         MemoryContext cxt;
  27 } TStoreState;
  28
  29
  30 /*
  31  * Prepare to receive tuples from executor.
  32  */
  33 static void
  34 tstoreStartupReceiver(DestReceiver *self, int operation, TupleDesc typeinfo)
  35 {
  36         /* do nothing */
  37 }
  38
  39 /*
  40  * Receive a tuple from the executor and store it in the tuplestore.
  41  */
  42 static void
  43 tstoreReceiveSlot(TupleTableSlot *slot, DestReceiver *self)
  44 {
  45         TStoreState *myState = (TStoreState *) self;
  46         MemoryContext oldcxt = MemoryContextSwitchTo(myState->cxt);
  47
  48         tuplestore_puttupleslot(myState->tstore, slot);
  49
  50         MemoryContextSwitchTo(oldcxt);
  51 }
  52
  53 /*
  54  * Clean up at end of an executor run
  55  */
  56 static void
  57 tstoreShutdownReceiver(DestReceiver *self)
  58 {
  59         /* do nothing */
  60 }
  61
  62 /*
  63  * Destroy receiver when done with it
  64  */
  65 static void
  66 tstoreDestroyReceiver(DestReceiver *self)
  67 {
  68         pfree(self);
  69 }
  70
  71 /*
  72  * Initially create a DestReceiver object.
  73  */
  74 DestReceiver *
  75 CreateTuplestoreDestReceiver(Tuplestorestate *tStore,
  76                                                          MemoryContext tContext)
  77 {
  78         TStoreState *self = (TStoreState *) palloc(sizeof(TStoreState));
  79
  80         self->pub.receiveSlot = tstoreReceiveSlot;
  81         self->pub.rStartup = tstoreStartupReceiver;
  82         self->pub.rShutdown = tstoreShutdownReceiver;
  83         self->pub.rDestroy = tstoreDestroyReceiver;
  84         self->pub.mydest = DestTuplestore;
  85
  86         self->tstore = tStore;
  87         self->cxt = tContext;
  88
  89         return (DestReceiver *) self;
  90 }