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) 1996-2016, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/executor/nodeFunctionscan.c
  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  *              ExecReScanFunctionScan  rescans the function
  22  */
  23 #include "postgres.h"
  24
  25 #include "catalog/pg_type.h"
  26 #include "executor/nodeFunctionscan.h"
  27 #include "funcapi.h"
  28 #include "nodes/nodeFuncs.h"
  29 #include "utils/builtins.h"
  30 #include "utils/memutils.h"
  31
  32
  33 /*
  34  * Runtime data for each function being scanned.
  35  */
  36 typedef struct FunctionScanPerFuncState
  37 {
  38         ExprState  *funcexpr;           /* state of the expression being evaluated */
  39         TupleDesc       tupdesc;                /* desc of the function result type */
  40         int                     colcount;               /* expected number of result columns */
  41         Tuplestorestate *tstore;        /* holds the function result set */
  42         int64           rowcount;               /* # of rows in result set, -1 if not known */
  43         TupleTableSlot *func_slot;      /* function result slot (or NULL) */
  44 } FunctionScanPerFuncState;
  45
  46 static TupleTableSlot *FunctionNext(FunctionScanState *node);
  47
  48
  49 /* ----------------------------------------------------------------
  50  *                                              Scan Support
  51  * ----------------------------------------------------------------
  52  */
  53 /* ----------------------------------------------------------------
  54  *              FunctionNext
  55  *
  56  *              This is a workhorse for ExecFunctionScan
  57  * ----------------------------------------------------------------
  58  */
  59 static TupleTableSlot *
  60 FunctionNext(FunctionScanState *node)
  61 {
  62         EState     *estate;
  63         ScanDirection direction;
  64         TupleTableSlot *scanslot;
  65         bool            alldone;
  66         int64           oldpos;
  67         int                     funcno;
  68         int                     att;
  69
  70         /*
  71          * get information from the estate and scan state
  72          */
  73         estate = node->ss.ps.state;
  74         direction = estate->es_direction;
  75         scanslot = node->ss.ss_ScanTupleSlot;
  76
  77         if (node->simple)
  78         {
  79                 /*
  80                  * Fast path for the trivial case: the function return type and scan
  81                  * result type are the same, so we fetch the function result straight
  82                  * into the scan result slot. No need to update ordinality or
  83                  * rowcounts either.
  84                  */
  85                 Tuplestorestate *tstore = node->funcstates[0].tstore;
  86
  87                 /*
  88                  * If first time through, read all tuples from function and put them
  89                  * in a tuplestore. Subsequent calls just fetch tuples from
  90                  * tuplestore.
  91                  */
  92                 if (tstore == NULL)
  93                 {
  94                         node->funcstates[0].tstore = tstore =
  95                                 ExecMakeTableFunctionResult(node->funcstates[0].funcexpr,
  96                                                                                         node->ss.ps.ps_ExprContext,
  97                                                                                         node->argcontext,
  98                                                                                         node->funcstates[0].tupdesc,
  99                                                                                   node->eflags & EXEC_FLAG_BACKWARD);
 100
 101                         /*
 102                          * paranoia - cope if the function, which may have constructed the
 103                          * tuplestore itself, didn't leave it pointing at the start. This
 104                          * call is fast, so the overhead shouldn't be an issue.
 105                          */
 106                         tuplestore_rescan(tstore);
 107                 }
 108
 109                 /*
 110                  * Get the next tuple from tuplestore.
 111                  */
 112                 (void) tuplestore_gettupleslot(tstore,
 113                                                                            ScanDirectionIsForward(direction),
 114                                                                            false,
 115                                                                            scanslot);
 116                 return scanslot;
 117         }
 118
 119         /*
 120          * Increment or decrement ordinal counter before checking for end-of-data,
 121          * so that we can move off either end of the result by 1 (and no more than
 122          * 1) without losing correct count.  See PortalRunSelect for why we can
 123          * assume that we won't be called repeatedly in the end-of-data state.
 124          */
 125         oldpos = node->ordinal;
 126         if (ScanDirectionIsForward(direction))
 127                 node->ordinal++;
 128         else
 129                 node->ordinal--;
 130
 131         /*
 132          * Main loop over functions.
 133          *
 134          * We fetch the function results into func_slots (which match the function
 135          * return types), and then copy the values to scanslot (which matches the
 136          * scan result type), setting the ordinal column (if any) as well.
 137          */
 138         ExecClearTuple(scanslot);
 139         att = 0;
 140         alldone = true;
 141         for (funcno = 0; funcno < node->nfuncs; funcno++)
 142         {
 143                 FunctionScanPerFuncState *fs = &node->funcstates[funcno];
 144                 int                     i;
 145
 146                 /*
 147                  * If first time through, read all tuples from function and put them
 148                  * in a tuplestore. Subsequent calls just fetch tuples from
 149                  * tuplestore.
 150                  */
 151                 if (fs->tstore == NULL)
 152                 {
 153                         fs->tstore =
 154                                 ExecMakeTableFunctionResult(fs->funcexpr,
 155                                                                                         node->ss.ps.ps_ExprContext,
 156                                                                                         node->argcontext,
 157                                                                                         fs->tupdesc,
 158                                                                                   node->eflags & EXEC_FLAG_BACKWARD);
 159
 160                         /*
 161                          * paranoia - cope if the function, which may have constructed the
 162                          * tuplestore itself, didn't leave it pointing at the start. This
 163                          * call is fast, so the overhead shouldn't be an issue.
 164                          */
 165                         tuplestore_rescan(fs->tstore);
 166                 }
 167
 168                 /*
 169                  * Get the next tuple from tuplestore.
 170                  *
 171                  * If we have a rowcount for the function, and we know the previous
 172                  * read position was out of bounds, don't try the read. This allows
 173                  * backward scan to work when there are mixed row counts present.
 174                  */
 175                 if (fs->rowcount != -1 && fs->rowcount < oldpos)
 176                         ExecClearTuple(fs->func_slot);
 177                 else
 178                         (void) tuplestore_gettupleslot(fs->tstore,
 179                                                                                    ScanDirectionIsForward(direction),
 180                                                                                    false,
 181                                                                                    fs->func_slot);
 182
 183                 if (TupIsNull(fs->func_slot))
 184                 {
 185                         /*
 186                          * If we ran out of data for this function in the forward
 187                          * direction then we now know how many rows it returned. We need
 188                          * to know this in order to handle backwards scans. The row count
 189                          * we store is actually 1+ the actual number, because we have to
 190                          * position the tuplestore 1 off its end sometimes.
 191                          */
 192                         if (ScanDirectionIsForward(direction) && fs->rowcount == -1)
 193                                 fs->rowcount = node->ordinal;
 194
 195                         /*
 196                          * populate the result cols with nulls
 197                          */
 198                         for (i = 0; i < fs->colcount; i++)
 199                         {
 200                                 scanslot->tts_values[att] = (Datum) 0;
 201                                 scanslot->tts_isnull[att] = true;
 202                                 att++;
 203                         }
 204                 }
 205                 else
 206                 {
 207                         /*
 208                          * we have a result, so just copy it to the result cols.
 209                          */
 210                         slot_getallattrs(fs->func_slot);
 211
 212                         for (i = 0; i < fs->colcount; i++)
 213                         {
 214                                 scanslot->tts_values[att] = fs->func_slot->tts_values[i];
 215                                 scanslot->tts_isnull[att] = fs->func_slot->tts_isnull[i];
 216                                 att++;
 217                         }
 218
 219                         /*
 220                          * We're not done until every function result is exhausted; we pad
 221                          * the shorter results with nulls until then.
 222                          */
 223                         alldone = false;
 224                 }
 225         }
 226
 227         /*
 228          * ordinal col is always last, per spec.
 229          */
 230         if (node->ordinality)
 231         {
 232                 scanslot->tts_values[att] = Int64GetDatumFast(node->ordinal);
 233                 scanslot->tts_isnull[att] = false;
 234         }
 235
 236         /*
 237          * If alldone, we just return the previously-cleared scanslot.  Otherwise,
 238          * finish creating the virtual tuple.
 239          */
 240         if (!alldone)
 241                 ExecStoreVirtualTuple(scanslot);
 242
 243         return scanslot;
 244 }
 245
 246 /*
 247  * FunctionRecheck -- access method routine to recheck a tuple in EvalPlanQual
 248  */
 249 static bool
 250 FunctionRecheck(FunctionScanState *node, TupleTableSlot *slot)
 251 {
 252         /* nothing to check */
 253         return true;
 254 }
 255
 256 /* ----------------------------------------------------------------
 257  *              ExecFunctionScan(node)
 258  *
 259  *              Scans the function sequentially and returns the next qualifying
 260  *              tuple.
 261  *              We call the ExecScan() routine and pass it the appropriate
 262  *              access method functions.
 263  * ----------------------------------------------------------------
 264  */
 265 TupleTableSlot *
 266 ExecFunctionScan(FunctionScanState *node)
 267 {
 268         return ExecScan(&node->ss,
 269                                         (ExecScanAccessMtd) FunctionNext,
 270                                         (ExecScanRecheckMtd) FunctionRecheck);
 271 }
 272
 273 /* ----------------------------------------------------------------
 274  *              ExecInitFunctionScan
 275  * ----------------------------------------------------------------
 276  */
 277 FunctionScanState *
 278 ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
 279 {
 280         FunctionScanState *scanstate;
 281         int                     nfuncs = list_length(node->functions);
 282         TupleDesc       scan_tupdesc;
 283         int                     i,
 284                                 natts;
 285         ListCell   *lc;
 286
 287         /* check for unsupported flags */
 288         Assert(!(eflags & EXEC_FLAG_MARK));
 289
 290         /*
 291          * FunctionScan should not have any children.
 292          */
 293         Assert(outerPlan(node) == NULL);
 294         Assert(innerPlan(node) == NULL);
 295
 296         /*
 297          * create new ScanState for node
 298          */
 299         scanstate = makeNode(FunctionScanState);
 300         scanstate->ss.ps.plan = (Plan *) node;
 301         scanstate->ss.ps.state = estate;
 302         scanstate->eflags = eflags;
 303
 304         /*
 305          * are we adding an ordinality column?
 306          */
 307         scanstate->ordinality = node->funcordinality;
 308
 309         scanstate->nfuncs = nfuncs;
 310         if (nfuncs == 1 && !node->funcordinality)
 311                 scanstate->simple = true;
 312         else
 313                 scanstate->simple = false;
 314
 315         /*
 316          * Ordinal 0 represents the "before the first row" position.
 317          *
 318          * We need to track ordinal position even when not adding an ordinality
 319          * column to the result, in order to handle backwards scanning properly
 320          * with multiple functions with different result sizes. (We can't position
 321          * any individual function's tuplestore any more than 1 place beyond its
 322          * end, so when scanning backwards, we need to know when to start
 323          * including the function in the scan again.)
 324          */
 325         scanstate->ordinal = 0;
 326
 327         /*
 328          * Miscellaneous initialization
 329          *
 330          * create expression context for node
 331          */
 332         ExecAssignExprContext(estate, &scanstate->ss.ps);
 333
 334         scanstate->ss.ps.ps_TupFromTlist = false;
 335
 336         /*
 337          * tuple table initialization
 338          */
 339         ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
 340         ExecInitScanTupleSlot(estate, &scanstate->ss);
 341
 342         /*
 343          * initialize child expressions
 344          */
 345         scanstate->ss.ps.targetlist = (List *)
 346                 ExecInitExpr((Expr *) node->scan.plan.targetlist,
 347                                          (PlanState *) scanstate);
 348         scanstate->ss.ps.qual = (List *)
 349                 ExecInitExpr((Expr *) node->scan.plan.qual,
 350                                          (PlanState *) scanstate);
 351
 352         scanstate->funcstates = palloc(nfuncs * sizeof(FunctionScanPerFuncState));
 353
 354         natts = 0;
 355         i = 0;
 356         foreach(lc, node->functions)
 357         {
 358                 RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
 359                 Node       *funcexpr = rtfunc->funcexpr;
 360                 int                     colcount = rtfunc->funccolcount;
 361                 FunctionScanPerFuncState *fs = &scanstate->funcstates[i];
 362                 TypeFuncClass functypclass;
 363                 Oid                     funcrettype;
 364                 TupleDesc       tupdesc;
 365
 366                 fs->funcexpr = ExecInitExpr((Expr *) funcexpr, (PlanState *) scanstate);
 367
 368                 /*
 369                  * Don't allocate the tuplestores; the actual calls to the functions
 370                  * do that.  NULL means that we have not called the function yet (or
 371                  * need to call it again after a rescan).
 372                  */
 373                 fs->tstore = NULL;
 374                 fs->rowcount = -1;
 375
 376                 /*
 377                  * Now determine if the function returns a simple or composite type,
 378                  * and build an appropriate tupdesc.  Note that in the composite case,
 379                  * the function may now return more columns than it did when the plan
 380                  * was made; we have to ignore any columns beyond "colcount".
 381                  */
 382                 functypclass = get_expr_result_type(funcexpr,
 383                                                                                         &funcrettype,
 384                                                                                         &tupdesc);
 385
 386                 if (functypclass == TYPEFUNC_COMPOSITE)
 387                 {
 388                         /* Composite data type, e.g. a table's row type */
 389                         Assert(tupdesc);
 390                         Assert(tupdesc->natts >= colcount);
 391                         /* Must copy it out of typcache for safety */
 392                         tupdesc = CreateTupleDescCopy(tupdesc);
 393                 }
 394                 else if (functypclass == TYPEFUNC_SCALAR)
 395                 {
 396                         /* Base data type, i.e. scalar */
 397                         tupdesc = CreateTemplateTupleDesc(1, false);
 398                         TupleDescInitEntry(tupdesc,
 399                                                            (AttrNumber) 1,
 400                                                            NULL,        /* don't care about the name here */
 401                                                            funcrettype,
 402                                                            -1,
 403                                                            0);
 404                         TupleDescInitEntryCollation(tupdesc,
 405                                                                                 (AttrNumber) 1,
 406                                                                                 exprCollation(funcexpr));
 407                 }
 408                 else if (functypclass == TYPEFUNC_RECORD)
 409                 {
 410                         tupdesc = BuildDescFromLists(rtfunc->funccolnames,
 411                                                                                  rtfunc->funccoltypes,
 412                                                                                  rtfunc->funccoltypmods,
 413                                                                                  rtfunc->funccolcollations);
 414
 415                         /*
 416                          * For RECORD results, make sure a typmod has been assigned.  (The
 417                          * function should do this for itself, but let's cover things in
 418                          * case it doesn't.)
 419                          */
 420                         BlessTupleDesc(tupdesc);
 421                 }
 422                 else
 423                 {
 424                         /* crummy error message, but parser should have caught this */
 425                         elog(ERROR, "function in FROM has unsupported return type");
 426                 }
 427
 428                 fs->tupdesc = tupdesc;
 429                 fs->colcount = colcount;
 430
 431                 /*
 432                  * We only need separate slots for the function results if we are
 433                  * doing ordinality or multiple functions; otherwise, we'll fetch
 434                  * function results directly into the scan slot.
 435                  */
 436                 if (!scanstate->simple)
 437                 {
 438                         fs->func_slot = ExecInitExtraTupleSlot(estate);
 439                         ExecSetSlotDescriptor(fs->func_slot, fs->tupdesc);
 440                 }
 441                 else
 442                         fs->func_slot = NULL;
 443
 444                 natts += colcount;
 445                 i++;
 446         }
 447
 448         /*
 449          * Create the combined TupleDesc
 450          *
 451          * If there is just one function without ordinality, the scan result
 452          * tupdesc is the same as the function result tupdesc --- except that we
 453          * may stuff new names into it below, so drop any rowtype label.
 454          */
 455         if (scanstate->simple)
 456         {
 457                 scan_tupdesc = CreateTupleDescCopy(scanstate->funcstates[0].tupdesc);
 458                 scan_tupdesc->tdtypeid = RECORDOID;
 459                 scan_tupdesc->tdtypmod = -1;
 460         }
 461         else
 462         {
 463                 AttrNumber      attno = 0;
 464
 465                 if (node->funcordinality)
 466                         natts++;
 467
 468                 scan_tupdesc = CreateTemplateTupleDesc(natts, false);
 469
 470                 for (i = 0; i < nfuncs; i++)
 471                 {
 472                         TupleDesc       tupdesc = scanstate->funcstates[i].tupdesc;
 473                         int                     colcount = scanstate->funcstates[i].colcount;
 474                         int                     j;
 475
 476                         for (j = 1; j <= colcount; j++)
 477                                 TupleDescCopyEntry(scan_tupdesc, ++attno, tupdesc, j);
 478                 }
 479
 480                 /* If doing ordinality, add a column of type "bigint" at the end */
 481                 if (node->funcordinality)
 482                 {
 483                         TupleDescInitEntry(scan_tupdesc,
 484                                                            ++attno,
 485                                                            NULL,        /* don't care about the name here */
 486                                                            INT8OID,
 487                                                            -1,
 488                                                            0);
 489                 }
 490
 491                 Assert(attno == natts);
 492         }
 493
 494         ExecAssignScanType(&scanstate->ss, scan_tupdesc);
 495
 496         /*
 497          * Initialize result tuple type and projection info.
 498          */
 499         ExecAssignResultTypeFromTL(&scanstate->ss.ps);
 500         ExecAssignScanProjectionInfo(&scanstate->ss);
 501
 502         /*
 503          * Create a memory context that ExecMakeTableFunctionResult can use to
 504          * evaluate function arguments in.  We can't use the per-tuple context for
 505          * this because it gets reset too often; but we don't want to leak
 506          * evaluation results into the query-lifespan context either.  We just
 507          * need one context, because we evaluate each function separately.
 508          */
 509         scanstate->argcontext = AllocSetContextCreate(CurrentMemoryContext,
 510                                                                                                   "Table function arguments",
 511                                                                                                   ALLOCSET_DEFAULT_SIZES);
 512
 513         return scanstate;
 514 }
 515
 516 /* ----------------------------------------------------------------
 517  *              ExecEndFunctionScan
 518  *
 519  *              frees any storage allocated through C routines.
 520  * ----------------------------------------------------------------
 521  */
 522 void
 523 ExecEndFunctionScan(FunctionScanState *node)
 524 {
 525         int                     i;
 526
 527         /*
 528          * Free the exprcontext
 529          */
 530         ExecFreeExprContext(&node->ss.ps);
 531
 532         /*
 533          * clean out the tuple table
 534          */
 535         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 536         ExecClearTuple(node->ss.ss_ScanTupleSlot);
 537
 538         /*
 539          * Release slots and tuplestore resources
 540          */
 541         for (i = 0; i < node->nfuncs; i++)
 542         {
 543                 FunctionScanPerFuncState *fs = &node->funcstates[i];
 544
 545                 if (fs->func_slot)
 546                         ExecClearTuple(fs->func_slot);
 547
 548                 if (fs->tstore != NULL)
 549                 {
 550                         tuplestore_end(node->funcstates[i].tstore);
 551                         fs->tstore = NULL;
 552                 }
 553         }
 554 }
 555
 556 /* ----------------------------------------------------------------
 557  *              ExecReScanFunctionScan
 558  *
 559  *              Rescans the relation.
 560  * ----------------------------------------------------------------
 561  */
 562 void
 563 ExecReScanFunctionScan(FunctionScanState *node)
 564 {
 565         FunctionScan *scan = (FunctionScan *) node->ss.ps.plan;
 566         int                     i;
 567         Bitmapset  *chgparam = node->ss.ps.chgParam;
 568
 569         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 570         for (i = 0; i < node->nfuncs; i++)
 571         {
 572                 FunctionScanPerFuncState *fs = &node->funcstates[i];
 573
 574                 if (fs->func_slot)
 575                         ExecClearTuple(fs->func_slot);
 576         }
 577
 578         ExecScanReScan(&node->ss);
 579
 580         /*
 581          * Here we have a choice whether to drop the tuplestores (and recompute
 582          * the function outputs) or just rescan them.  We must recompute if an
 583          * expression contains changed parameters, else we rescan.
 584          *
 585          * XXX maybe we should recompute if the function is volatile?  But in
 586          * general the executor doesn't conditionalize its actions on that.
 587          */
 588         if (chgparam)
 589         {
 590                 ListCell   *lc;
 591
 592                 i = 0;
 593                 foreach(lc, scan->functions)
 594                 {
 595                         RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
 596
 597                         if (bms_overlap(chgparam, rtfunc->funcparams))
 598                         {
 599                                 if (node->funcstates[i].tstore != NULL)
 600                                 {
 601                                         tuplestore_end(node->funcstates[i].tstore);
 602                                         node->funcstates[i].tstore = NULL;
 603                                 }
 604                                 node->funcstates[i].rowcount = -1;
 605                         }
 606                         i++;
 607                 }
 608         }
 609
 610         /* Reset ordinality counter */
 611         node->ordinal = 0;
 612
 613         /* Make sure we rewind any remaining tuplestores */
 614         for (i = 0; i < node->nfuncs; i++)
 615         {
 616                 if (node->funcstates[i].tstore != NULL)
 617                         tuplestore_rescan(node->funcstates[i].tstore);
 618         }
 619 }