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

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeFunctionscan.c
   4  *        Support routines for scanning RangeFunctions (functions in rangetable).
   5  *
   6  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL: pgsql/src/backend/executor/nodeFunctionscan.c,v 1.49 2008/10/29 00:00:38 tgl Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 /*
  16  * INTERFACE ROUTINES
  17  *              ExecFunctionScan                scans a function.
  18  *              ExecFunctionNext                retrieve next tuple in sequential order.
  19  *              ExecInitFunctionScan    creates and initializes a functionscan node.
  20  *              ExecEndFunctionScan             releases any storage allocated.
  21  *              ExecFunctionReScan              rescans the function
  22  */
  23 #include "postgres.h"
  24
  25 #include "executor/nodeFunctionscan.h"
  26 #include "funcapi.h"
  27 #include "utils/builtins.h"
  28
  29
  30 static TupleTableSlot *FunctionNext(FunctionScanState *node);
  31
  32 /* ----------------------------------------------------------------
  33  *                                              Scan Support
  34  * ----------------------------------------------------------------
  35  */
  36 /* ----------------------------------------------------------------
  37  *              FunctionNext
  38  *
  39  *              This is a workhorse for ExecFunctionScan
  40  * ----------------------------------------------------------------
  41  */
  42 static TupleTableSlot *
  43 FunctionNext(FunctionScanState *node)
  44 {
  45         TupleTableSlot *slot;
  46         EState     *estate;
  47         ScanDirection direction;
  48         Tuplestorestate *tuplestorestate;
  49
  50         /*
  51          * get information from the estate and scan state
  52          */
  53         estate = node->ss.ps.state;
  54         direction = estate->es_direction;
  55
  56         tuplestorestate = node->tuplestorestate;
  57
  58         /*
  59          * If first time through, read all tuples from function and put them in a
  60          * tuplestore. Subsequent calls just fetch tuples from tuplestore.
  61          */
  62         if (tuplestorestate == NULL)
  63         {
  64                 node->tuplestorestate = tuplestorestate =
  65                         ExecMakeTableFunctionResult(node->funcexpr,
  66                                                                                 node->ss.ps.ps_ExprContext,
  67                                                                                 node->tupdesc,
  68                                                                                 node->eflags & EXEC_FLAG_BACKWARD);
  69         }
  70
  71         /*
  72          * Get the next tuple from tuplestore. Return NULL if no more tuples.
  73          */
  74         slot = node->ss.ss_ScanTupleSlot;
  75         (void) tuplestore_gettupleslot(tuplestorestate,
  76                                                                    ScanDirectionIsForward(direction),
  77                                                                    slot);
  78         return slot;
  79 }
  80
  81 /* ----------------------------------------------------------------
  82  *              ExecFunctionScan(node)
  83  *
  84  *              Scans the function sequentially and returns the next qualifying
  85  *              tuple.
  86  *              It calls the ExecScan() routine and passes it the access method
  87  *              which retrieves tuples sequentially.
  88  *
  89  */
  90
  91 TupleTableSlot *
  92 ExecFunctionScan(FunctionScanState *node)
  93 {
  94         /*
  95          * use FunctionNext as access method
  96          */
  97         return ExecScan(&node->ss, (ExecScanAccessMtd) FunctionNext);
  98 }
  99
 100 /* ----------------------------------------------------------------
 101  *              ExecInitFunctionScan
 102  * ----------------------------------------------------------------
 103  */
 104 FunctionScanState *
 105 ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
 106 {
 107         FunctionScanState *scanstate;
 108         Oid                     funcrettype;
 109         TypeFuncClass functypclass;
 110         TupleDesc       tupdesc = NULL;
 111
 112         /* check for unsupported flags */
 113         Assert(!(eflags & EXEC_FLAG_MARK));
 114
 115         /*
 116          * FunctionScan should not have any children.
 117          */
 118         Assert(outerPlan(node) == NULL);
 119         Assert(innerPlan(node) == NULL);
 120
 121         /*
 122          * create new ScanState for node
 123          */
 124         scanstate = makeNode(FunctionScanState);
 125         scanstate->ss.ps.plan = (Plan *) node;
 126         scanstate->ss.ps.state = estate;
 127         scanstate->eflags = eflags;
 128
 129         /*
 130          * Miscellaneous initialization
 131          *
 132          * create expression context for node
 133          */
 134         ExecAssignExprContext(estate, &scanstate->ss.ps);
 135
 136 #define FUNCTIONSCAN_NSLOTS 2
 137
 138         /*
 139          * tuple table initialization
 140          */
 141         ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
 142         ExecInitScanTupleSlot(estate, &scanstate->ss);
 143
 144         /*
 145          * initialize child expressions
 146          */
 147         scanstate->ss.ps.targetlist = (List *)
 148                 ExecInitExpr((Expr *) node->scan.plan.targetlist,
 149                                          (PlanState *) scanstate);
 150         scanstate->ss.ps.qual = (List *)
 151                 ExecInitExpr((Expr *) node->scan.plan.qual,
 152                                          (PlanState *) scanstate);
 153
 154         /*
 155          * Now determine if the function returns a simple or composite type, and
 156          * build an appropriate tupdesc.
 157          */
 158         functypclass = get_expr_result_type(node->funcexpr,
 159                                                                                 &funcrettype,
 160                                                                                 &tupdesc);
 161
 162         if (functypclass == TYPEFUNC_COMPOSITE)
 163         {
 164                 /* Composite data type, e.g. a table's row type */
 165                 Assert(tupdesc);
 166                 /* Must copy it out of typcache for safety */
 167                 tupdesc = CreateTupleDescCopy(tupdesc);
 168         }
 169         else if (functypclass == TYPEFUNC_SCALAR)
 170         {
 171                 /* Base data type, i.e. scalar */
 172                 char       *attname = strVal(linitial(node->funccolnames));
 173
 174                 tupdesc = CreateTemplateTupleDesc(1, false);
 175                 TupleDescInitEntry(tupdesc,
 176                                                    (AttrNumber) 1,
 177                                                    attname,
 178                                                    funcrettype,
 179                                                    -1,
 180                                                    0);
 181         }
 182         else if (functypclass == TYPEFUNC_RECORD)
 183         {
 184                 tupdesc = BuildDescFromLists(node->funccolnames,
 185                                                                          node->funccoltypes,
 186                                                                          node->funccoltypmods);
 187         }
 188         else
 189         {
 190                 /* crummy error message, but parser should have caught this */
 191                 elog(ERROR, "function in FROM has unsupported return type");
 192         }
 193
 194         /*
 195          * For RECORD results, make sure a typmod has been assigned.  (The
 196          * function should do this for itself, but let's cover things in case it
 197          * doesn't.)
 198          */
 199         BlessTupleDesc(tupdesc);
 200
 201         scanstate->tupdesc = tupdesc;
 202         ExecAssignScanType(&scanstate->ss, tupdesc);
 203
 204         /*
 205          * Other node-specific setup
 206          */
 207         scanstate->tuplestorestate = NULL;
 208         scanstate->funcexpr = ExecInitExpr((Expr *) node->funcexpr,
 209                                                                            (PlanState *) scanstate);
 210
 211         scanstate->ss.ps.ps_TupFromTlist = false;
 212
 213         /*
 214          * Initialize result tuple type and projection info.
 215          */
 216         ExecAssignResultTypeFromTL(&scanstate->ss.ps);
 217         ExecAssignScanProjectionInfo(&scanstate->ss);
 218
 219         return scanstate;
 220 }
 221
 222 int
 223 ExecCountSlotsFunctionScan(FunctionScan *node)
 224 {
 225         return ExecCountSlotsNode(outerPlan(node)) +
 226                 ExecCountSlotsNode(innerPlan(node)) +
 227                 FUNCTIONSCAN_NSLOTS;
 228 }
 229
 230 /* ----------------------------------------------------------------
 231  *              ExecEndFunctionScan
 232  *
 233  *              frees any storage allocated through C routines.
 234  * ----------------------------------------------------------------
 235  */
 236 void
 237 ExecEndFunctionScan(FunctionScanState *node)
 238 {
 239         /*
 240          * Free the exprcontext
 241          */
 242         ExecFreeExprContext(&node->ss.ps);
 243
 244         /*
 245          * clean out the tuple table
 246          */
 247         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 248         ExecClearTuple(node->ss.ss_ScanTupleSlot);
 249
 250         /*
 251          * Release tuplestore resources
 252          */
 253         if (node->tuplestorestate != NULL)
 254                 tuplestore_end(node->tuplestorestate);
 255         node->tuplestorestate = NULL;
 256 }
 257
 258 /* ----------------------------------------------------------------
 259  *              ExecFunctionReScan
 260  *
 261  *              Rescans the relation.
 262  * ----------------------------------------------------------------
 263  */
 264 void
 265 ExecFunctionReScan(FunctionScanState *node, ExprContext *exprCtxt)
 266 {
 267         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 268         node->ss.ps.ps_TupFromTlist = false;
 269
 270         /*
 271          * If we haven't materialized yet, just return.
 272          */
 273         if (!node->tuplestorestate)
 274                 return;
 275
 276         /*
 277          * Here we have a choice whether to drop the tuplestore (and recompute the
 278          * function outputs) or just rescan it.  We must recompute if the
 279          * expression contains parameters, else we rescan.  XXX maybe we should
 280          * recompute if the function is volatile?
 281          */
 282         if (node->ss.ps.chgParam != NULL)
 283         {
 284                 tuplestore_end(node->tuplestorestate);
 285                 node->tuplestorestate = NULL;
 286         }
 287         else
 288                 tuplestore_rescan(node->tuplestorestate);
 289 }