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) 1996-2017, 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         /*
 335          * tuple table initialization
 336          */
 337         ExecInitResultTupleSlot(estate, &scanstate->ss.ps);
 338         ExecInitScanTupleSlot(estate, &scanstate->ss);
 339
 340         /*
 341          * initialize child expressions
 342          */
 343         scanstate->ss.ps.targetlist = (List *)
 344                 ExecInitExpr((Expr *) node->scan.plan.targetlist,
 345                                          (PlanState *) scanstate);
 346         scanstate->ss.ps.qual = (List *)
 347                 ExecInitExpr((Expr *) node->scan.plan.qual,
 348                                          (PlanState *) scanstate);
 349
 350         scanstate->funcstates = palloc(nfuncs * sizeof(FunctionScanPerFuncState));
 351
 352         natts = 0;
 353         i = 0;
 354         foreach(lc, node->functions)
 355         {
 356                 RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
 357                 Node       *funcexpr = rtfunc->funcexpr;
 358                 int                     colcount = rtfunc->funccolcount;
 359                 FunctionScanPerFuncState *fs = &scanstate->funcstates[i];
 360                 TypeFuncClass functypclass;
 361                 Oid                     funcrettype;
 362                 TupleDesc       tupdesc;
 363
 364                 fs->funcexpr = ExecInitExpr((Expr *) funcexpr, (PlanState *) scanstate);
 365
 366                 /*
 367                  * Don't allocate the tuplestores; the actual calls to the functions
 368                  * do that.  NULL means that we have not called the function yet (or
 369                  * need to call it again after a rescan).
 370                  */
 371                 fs->tstore = NULL;
 372                 fs->rowcount = -1;
 373
 374                 /*
 375                  * Now determine if the function returns a simple or composite type,
 376                  * and build an appropriate tupdesc.  Note that in the composite case,
 377                  * the function may now return more columns than it did when the plan
 378                  * was made; we have to ignore any columns beyond "colcount".
 379                  */
 380                 functypclass = get_expr_result_type(funcexpr,
 381                                                                                         &funcrettype,
 382                                                                                         &tupdesc);
 383
 384                 if (functypclass == TYPEFUNC_COMPOSITE)
 385                 {
 386                         /* Composite data type, e.g. a table's row type */
 387                         Assert(tupdesc);
 388                         Assert(tupdesc->natts >= colcount);
 389                         /* Must copy it out of typcache for safety */
 390                         tupdesc = CreateTupleDescCopy(tupdesc);
 391                 }
 392                 else if (functypclass == TYPEFUNC_SCALAR)
 393                 {
 394                         /* Base data type, i.e. scalar */
 395                         tupdesc = CreateTemplateTupleDesc(1, false);
 396                         TupleDescInitEntry(tupdesc,
 397                                                            (AttrNumber) 1,
 398                                                            NULL,        /* don't care about the name here */
 399                                                            funcrettype,
 400                                                            -1,
 401                                                            0);
 402                         TupleDescInitEntryCollation(tupdesc,
 403                                                                                 (AttrNumber) 1,
 404                                                                                 exprCollation(funcexpr));
 405                 }
 406                 else if (functypclass == TYPEFUNC_RECORD)
 407                 {
 408                         tupdesc = BuildDescFromLists(rtfunc->funccolnames,
 409                                                                                  rtfunc->funccoltypes,
 410                                                                                  rtfunc->funccoltypmods,
 411                                                                                  rtfunc->funccolcollations);
 412
 413                         /*
 414                          * For RECORD results, make sure a typmod has been assigned.  (The
 415                          * function should do this for itself, but let's cover things in
 416                          * case it doesn't.)
 417                          */
 418                         BlessTupleDesc(tupdesc);
 419                 }
 420                 else
 421                 {
 422                         /* crummy error message, but parser should have caught this */
 423                         elog(ERROR, "function in FROM has unsupported return type");
 424                 }
 425
 426                 fs->tupdesc = tupdesc;
 427                 fs->colcount = colcount;
 428
 429                 /*
 430                  * We only need separate slots for the function results if we are
 431                  * doing ordinality or multiple functions; otherwise, we'll fetch
 432                  * function results directly into the scan slot.
 433                  */
 434                 if (!scanstate->simple)
 435                 {
 436                         fs->func_slot = ExecInitExtraTupleSlot(estate);
 437                         ExecSetSlotDescriptor(fs->func_slot, fs->tupdesc);
 438                 }
 439                 else
 440                         fs->func_slot = NULL;
 441
 442                 natts += colcount;
 443                 i++;
 444         }
 445
 446         /*
 447          * Create the combined TupleDesc
 448          *
 449          * If there is just one function without ordinality, the scan result
 450          * tupdesc is the same as the function result tupdesc --- except that we
 451          * may stuff new names into it below, so drop any rowtype label.
 452          */
 453         if (scanstate->simple)
 454         {
 455                 scan_tupdesc = CreateTupleDescCopy(scanstate->funcstates[0].tupdesc);
 456                 scan_tupdesc->tdtypeid = RECORDOID;
 457                 scan_tupdesc->tdtypmod = -1;
 458         }
 459         else
 460         {
 461                 AttrNumber      attno = 0;
 462
 463                 if (node->funcordinality)
 464                         natts++;
 465
 466                 scan_tupdesc = CreateTemplateTupleDesc(natts, false);
 467
 468                 for (i = 0; i < nfuncs; i++)
 469                 {
 470                         TupleDesc       tupdesc = scanstate->funcstates[i].tupdesc;
 471                         int                     colcount = scanstate->funcstates[i].colcount;
 472                         int                     j;
 473
 474                         for (j = 1; j <= colcount; j++)
 475                                 TupleDescCopyEntry(scan_tupdesc, ++attno, tupdesc, j);
 476                 }
 477
 478                 /* If doing ordinality, add a column of type "bigint" at the end */
 479                 if (node->funcordinality)
 480                 {
 481                         TupleDescInitEntry(scan_tupdesc,
 482                                                            ++attno,
 483                                                            NULL,        /* don't care about the name here */
 484                                                            INT8OID,
 485                                                            -1,
 486                                                            0);
 487                 }
 488
 489                 Assert(attno == natts);
 490         }
 491
 492         ExecAssignScanType(&scanstate->ss, scan_tupdesc);
 493
 494         /*
 495          * Initialize result tuple type and projection info.
 496          */
 497         ExecAssignResultTypeFromTL(&scanstate->ss.ps);
 498         ExecAssignScanProjectionInfo(&scanstate->ss);
 499
 500         /*
 501          * Create a memory context that ExecMakeTableFunctionResult can use to
 502          * evaluate function arguments in.  We can't use the per-tuple context for
 503          * this because it gets reset too often; but we don't want to leak
 504          * evaluation results into the query-lifespan context either.  We just
 505          * need one context, because we evaluate each function separately.
 506          */
 507         scanstate->argcontext = AllocSetContextCreate(CurrentMemoryContext,
 508                                                                                                   "Table function arguments",
 509                                                                                                   ALLOCSET_DEFAULT_SIZES);
 510
 511         return scanstate;
 512 }
 513
 514 /* ----------------------------------------------------------------
 515  *              ExecEndFunctionScan
 516  *
 517  *              frees any storage allocated through C routines.
 518  * ----------------------------------------------------------------
 519  */
 520 void
 521 ExecEndFunctionScan(FunctionScanState *node)
 522 {
 523         int                     i;
 524
 525         /*
 526          * Free the exprcontext
 527          */
 528         ExecFreeExprContext(&node->ss.ps);
 529
 530         /*
 531          * clean out the tuple table
 532          */
 533         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 534         ExecClearTuple(node->ss.ss_ScanTupleSlot);
 535
 536         /*
 537          * Release slots and tuplestore resources
 538          */
 539         for (i = 0; i < node->nfuncs; i++)
 540         {
 541                 FunctionScanPerFuncState *fs = &node->funcstates[i];
 542
 543                 if (fs->func_slot)
 544                         ExecClearTuple(fs->func_slot);
 545
 546                 if (fs->tstore != NULL)
 547                 {
 548                         tuplestore_end(node->funcstates[i].tstore);
 549                         fs->tstore = NULL;
 550                 }
 551         }
 552 }
 553
 554 /* ----------------------------------------------------------------
 555  *              ExecReScanFunctionScan
 556  *
 557  *              Rescans the relation.
 558  * ----------------------------------------------------------------
 559  */
 560 void
 561 ExecReScanFunctionScan(FunctionScanState *node)
 562 {
 563         FunctionScan *scan = (FunctionScan *) node->ss.ps.plan;
 564         int                     i;
 565         Bitmapset  *chgparam = node->ss.ps.chgParam;
 566
 567         ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
 568         for (i = 0; i < node->nfuncs; i++)
 569         {
 570                 FunctionScanPerFuncState *fs = &node->funcstates[i];
 571
 572                 if (fs->func_slot)
 573                         ExecClearTuple(fs->func_slot);
 574         }
 575
 576         ExecScanReScan(&node->ss);
 577
 578         /*
 579          * Here we have a choice whether to drop the tuplestores (and recompute
 580          * the function outputs) or just rescan them.  We must recompute if an
 581          * expression contains changed parameters, else we rescan.
 582          *
 583          * XXX maybe we should recompute if the function is volatile?  But in
 584          * general the executor doesn't conditionalize its actions on that.
 585          */
 586         if (chgparam)
 587         {
 588                 ListCell   *lc;
 589
 590                 i = 0;
 591                 foreach(lc, scan->functions)
 592                 {
 593                         RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
 594
 595                         if (bms_overlap(chgparam, rtfunc->funcparams))
 596                         {
 597                                 if (node->funcstates[i].tstore != NULL)
 598                                 {
 599                                         tuplestore_end(node->funcstates[i].tstore);
 600                                         node->funcstates[i].tstore = NULL;
 601                                 }
 602                                 node->funcstates[i].rowcount = -1;
 603                         }
 604                         i++;
 605                 }
 606         }
 607
 608         /* Reset ordinality counter */
 609         node->ordinal = 0;
 610
 611         /* Make sure we rewind any remaining tuplestores */
 612         for (i = 0; i < node->nfuncs; i++)
 613         {
 614                 if (node->funcstates[i].tstore != NULL)
 615                         tuplestore_rescan(node->funcstates[i].tstore);
 616         }
 617 }