src/backend/executor/nodeFunctionscan.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeFunctionscan.c
   4  *        Support routines for scanning RangeFunctions (functions in rangetable).
   5  *
   6  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $PostgreSQL$
  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                                                                    false,
  78                                                                    slot);
  79         return slot;
  80 }
  81
  82 /* ----------------------------------------------------------------
  83  *              ExecFunctionScan(node)
  84  *
  85  *              Scans the function sequentially and returns the next qualifying
  86  *              tuple.
  87  *              It calls the ExecScan() routine and passes it the access method
  88  *              which retrieves tuples sequentially.
  89  *
  90  */
  91
  92 TupleTableSlot *
  93 ExecFunctionScan(FunctionScanState *node)
  94 {
  95         /*
  96          * use FunctionNext as access method
  97          */
  98         return ExecScan(&node->ss, (ExecScanAccessMtd) FunctionNext);
  99 }
 100
 101 /* ----------------------------------------------------------------
 102  *              ExecInitFunctionScan
 103  * ----------------------------------------------------------------
 104  */
 105 FunctionScanState *
 106 ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
 107 {
 108         FunctionScanState *scanstate;
 109         Oid                     funcrettype;
 110         TypeFuncClass functypclass;
 111         TupleDesc       tupdesc = NULL;
 112
 113         /* check for unsupported flags */
 114         Assert(!(eflags & EXEC_FLAG_MARK));
 115
 116         /*
 117          * FunctionScan should not have any children.
 118          */
 119         Assert(outerPlan(node) == NULL);
 120         Assert(innerPlan(node) == NULL);
 121
 122         /*
 123          * create new ScanState for node
 124          */
 125         scanstate = makeNode(FunctionScanState);
 126         scanstate->ss.ps.plan = (Plan *) node;
 127         scanstate->ss.ps.state = estate;
 128         scanstate->eflags = eflags;
 129
 130         /*
 131          * Miscellaneous initialization
 132          *
 133          * create expression context for node
 134          */
 135         ExecAssignExprContext(estate, &scanstate->ss.ps);
 136
 137 #define FUNCTIONSCAN_NSLOTS 2
 138
 139         /*
 140          * tuple table initialization
 141          */
 142         ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
 143         ExecInitScanTupleSlot(estate, &scanstate->ss);
 144
 145         /*
 146          * initialize child expressions
 147          */
 148         scanstate->ss.ps.targetlist = (List *)
 149                 ExecInitExpr((Expr *) node->scan.plan.targetlist,
 150                                          (PlanState *) scanstate);
 151         scanstate->ss.ps.qual = (List *)
 152                 ExecInitExpr((Expr *) node->scan.plan.qual,
 153                                          (PlanState *) scanstate);
 154
 155         /*
 156          * Now determine if the function returns a simple or composite type, and
 157          * build an appropriate tupdesc.
 158          */
 159         functypclass = get_expr_result_type(node->funcexpr,
 160                                                                                 &funcrettype,
 161                                                                                 &tupdesc);
 162
 163         if (functypclass == TYPEFUNC_COMPOSITE)
 164         {
 165                 /* Composite data type, e.g. a table's row type */
 166                 Assert(tupdesc);
 167                 /* Must copy it out of typcache for safety */
 168                 tupdesc = CreateTupleDescCopy(tupdesc);
 169         }
 170         else if (functypclass == TYPEFUNC_SCALAR)
 171         {
 172                 /* Base data type, i.e. scalar */
 173                 char       *attname = strVal(linitial(node->funccolnames));
 174
 175                 tupdesc = CreateTemplateTupleDesc(1, false);
 176                 TupleDescInitEntry(tupdesc,
 177                                                    (AttrNumber) 1,
 178                                                    attname,
 179                                                    funcrettype,
 180                                                    -1,
 181                                                    0);
 182         }
 183         else if (functypclass == TYPEFUNC_RECORD)
 184         {
 185                 tupdesc = BuildDescFromLists(node->funccolnames,
 186                                                                          node->funccoltypes,
 187                                                                          node->funccoltypmods);
 188         }
 189         else
 190         {
 191                 /* crummy error message, but parser should have caught this */
 192                 elog(ERROR, "function in FROM has unsupported return type");
 193         }
 194
 195         /*
 196          * For RECORD results, make sure a typmod has been assigned.  (The
 197          * function should do this for itself, but let's cover things in case it
 198          * doesn't.)
 199          */
 200         BlessTupleDesc(tupdesc);
 201
 202         scanstate->tupdesc = tupdesc;
 203         ExecAssignScanType(&scanstate->ss, tupdesc);
 204
 205         /*
 206          * Other node-specific setup
 207          */
 208         scanstate->tuplestorestate = NULL;
 209         scanstate->funcexpr = ExecInitExpr((Expr *) node->funcexpr,
 210                                                                            (PlanState *) scanstate);
 211
 212         scanstate->ss.ps.ps_TupFromTlist = false;
 213
 214         /*
 215          * Initialize result tuple type and projection info.
 216          */
 217         ExecAssignResultTypeFromTL(&scanstate->ss.ps);
 218         ExecAssignScanProjectionInfo(&scanstate->ss);
 219
 220         return scanstate;
 221 }
 222
 223 int
 224 ExecCountSlotsFunctionScan(FunctionScan *node)
 225 {
 226         return ExecCountSlotsNode(outerPlan(node)) +
 227                 ExecCountSlotsNode(innerPlan(node)) +
 228                 FUNCTIONSCAN_NSLOTS;
 229 }
 230
 231 /* ----------------------------------------------------------------
 232  *              ExecEndFunctionScan
 233  *
 234  *              frees any storage allocated through C routines.
 235  * ----------------------------------------------------------------
 236  */
 237 void
 238 ExecEndFunctionScan(FunctionScanState *node)
 239 {
 240         /*
 241          * Free the exprcontext
 242          */
 243         ExecFreeExprContext(&node->ss.ps);
 244
 245         /*
 246          * clean out the tuple table
 247          */
 248         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 249         ExecClearTuple(node->ss.ss_ScanTupleSlot);
 250
 251         /*
 252          * Release tuplestore resources
 253          */
 254         if (node->tuplestorestate != NULL)
 255                 tuplestore_end(node->tuplestorestate);
 256         node->tuplestorestate = NULL;
 257 }
 258
 259 /* ----------------------------------------------------------------
 260  *              ExecFunctionReScan
 261  *
 262  *              Rescans the relation.
 263  * ----------------------------------------------------------------
 264  */
 265 void
 266 ExecFunctionReScan(FunctionScanState *node, ExprContext *exprCtxt)
 267 {
 268         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 269         node->ss.ps.ps_TupFromTlist = false;
 270
 271         /*
 272          * If we haven't materialized yet, just return.
 273          */
 274         if (!node->tuplestorestate)
 275                 return;
 276
 277         /*
 278          * Here we have a choice whether to drop the tuplestore (and recompute the
 279          * function outputs) or just rescan it.  We must recompute if the
 280          * expression contains parameters, else we rescan.      XXX maybe we should
 281          * recompute if the function is volatile?
 282          */
 283         if (node->ss.ps.chgParam != NULL)
 284         {
 285                 tuplestore_end(node->tuplestorestate);
 286                 node->tuplestorestate = NULL;
 287         }
 288         else
 289                 tuplestore_rescan(node->tuplestorestate);
 290 }