1 /*-------------------------------------------------------------------------
2 *
3 * nodeFunctionscan.c
4 * Support routines for scanning RangeFunctions (functions in rangetable).
5 *
6 * Portions Copyright (c) 1996-2018, 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 SetExprState *setexpr; /* 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 *
FunctionNext(FunctionScanState * node)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].setexpr,
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->setexpr,
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
FunctionRecheck(FunctionScanState * node,TupleTableSlot * slot)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 static TupleTableSlot *
ExecFunctionScan(PlanState * pstate)266 ExecFunctionScan(PlanState *pstate)
267 {
268 FunctionScanState *node = castNode(FunctionScanState, pstate);
269
270 return ExecScan(&node->ss,
271 (ExecScanAccessMtd) FunctionNext,
272 (ExecScanRecheckMtd) FunctionRecheck);
273 }
274
275 /* ----------------------------------------------------------------
276 * ExecInitFunctionScan
277 * ----------------------------------------------------------------
278 */
279 FunctionScanState *
ExecInitFunctionScan(FunctionScan * node,EState * estate,int eflags)280 ExecInitFunctionScan(FunctionScan *node, EState *estate, int eflags)
281 {
282 FunctionScanState *scanstate;
283 int nfuncs = list_length(node->functions);
284 TupleDesc scan_tupdesc;
285 int i,
286 natts;
287 ListCell *lc;
288
289 /* check for unsupported flags */
290 Assert(!(eflags & EXEC_FLAG_MARK));
291
292 /*
293 * FunctionScan should not have any children.
294 */
295 Assert(outerPlan(node) == NULL);
296 Assert(innerPlan(node) == NULL);
297
298 /*
299 * create new ScanState for node
300 */
301 scanstate = makeNode(FunctionScanState);
302 scanstate->ss.ps.plan = (Plan *) node;
303 scanstate->ss.ps.state = estate;
304 scanstate->ss.ps.ExecProcNode = ExecFunctionScan;
305 scanstate->eflags = eflags;
306
307 /*
308 * are we adding an ordinality column?
309 */
310 scanstate->ordinality = node->funcordinality;
311
312 scanstate->nfuncs = nfuncs;
313 if (nfuncs == 1 && !node->funcordinality)
314 scanstate->simple = true;
315 else
316 scanstate->simple = false;
317
318 /*
319 * Ordinal 0 represents the "before the first row" position.
320 *
321 * We need to track ordinal position even when not adding an ordinality
322 * column to the result, in order to handle backwards scanning properly
323 * with multiple functions with different result sizes. (We can't position
324 * any individual function's tuplestore any more than 1 place beyond its
325 * end, so when scanning backwards, we need to know when to start
326 * including the function in the scan again.)
327 */
328 scanstate->ordinal = 0;
329
330 /*
331 * Miscellaneous initialization
332 *
333 * create expression context for node
334 */
335 ExecAssignExprContext(estate, &scanstate->ss.ps);
336
337 scanstate->funcstates = palloc(nfuncs * sizeof(FunctionScanPerFuncState));
338
339 natts = 0;
340 i = 0;
341 foreach(lc, node->functions)
342 {
343 RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
344 Node *funcexpr = rtfunc->funcexpr;
345 int colcount = rtfunc->funccolcount;
346 FunctionScanPerFuncState *fs = &scanstate->funcstates[i];
347 TypeFuncClass functypclass;
348 Oid funcrettype;
349 TupleDesc tupdesc;
350
351 fs->setexpr =
352 ExecInitTableFunctionResult((Expr *) funcexpr,
353 scanstate->ss.ps.ps_ExprContext,
354 &scanstate->ss.ps);
355
356 /*
357 * Don't allocate the tuplestores; the actual calls to the functions
358 * do that. NULL means that we have not called the function yet (or
359 * need to call it again after a rescan).
360 */
361 fs->tstore = NULL;
362 fs->rowcount = -1;
363
364 /*
365 * Now determine if the function returns a simple or composite type,
366 * and build an appropriate tupdesc. Note that in the composite case,
367 * the function may now return more columns than it did when the plan
368 * was made; we have to ignore any columns beyond "colcount".
369 */
370 functypclass = get_expr_result_type(funcexpr,
371 &funcrettype,
372 &tupdesc);
373
374 if (functypclass == TYPEFUNC_COMPOSITE ||
375 functypclass == TYPEFUNC_COMPOSITE_DOMAIN)
376 {
377 /* Composite data type, e.g. a table's row type */
378 Assert(tupdesc);
379 Assert(tupdesc->natts >= colcount);
380 /* Must copy it out of typcache for safety */
381 tupdesc = CreateTupleDescCopy(tupdesc);
382 }
383 else if (functypclass == TYPEFUNC_SCALAR)
384 {
385 /* Base data type, i.e. scalar */
386 tupdesc = CreateTemplateTupleDesc(1, false);
387 TupleDescInitEntry(tupdesc,
388 (AttrNumber) 1,
389 NULL, /* don't care about the name here */
390 funcrettype,
391 -1,
392 0);
393 TupleDescInitEntryCollation(tupdesc,
394 (AttrNumber) 1,
395 exprCollation(funcexpr));
396 }
397 else if (functypclass == TYPEFUNC_RECORD)
398 {
399 tupdesc = BuildDescFromLists(rtfunc->funccolnames,
400 rtfunc->funccoltypes,
401 rtfunc->funccoltypmods,
402 rtfunc->funccolcollations);
403
404 /*
405 * For RECORD results, make sure a typmod has been assigned. (The
406 * function should do this for itself, but let's cover things in
407 * case it doesn't.)
408 */
409 BlessTupleDesc(tupdesc);
410 }
411 else
412 {
413 /* crummy error message, but parser should have caught this */
414 elog(ERROR, "function in FROM has unsupported return type");
415 }
416
417 fs->tupdesc = tupdesc;
418 fs->colcount = colcount;
419
420 /*
421 * We only need separate slots for the function results if we are
422 * doing ordinality or multiple functions; otherwise, we'll fetch
423 * function results directly into the scan slot.
424 */
425 if (!scanstate->simple)
426 {
427 fs->func_slot = ExecInitExtraTupleSlot(estate, fs->tupdesc);
428 }
429 else
430 fs->func_slot = NULL;
431
432 natts += colcount;
433 i++;
434 }
435
436 /*
437 * Create the combined TupleDesc
438 *
439 * If there is just one function without ordinality, the scan result
440 * tupdesc is the same as the function result tupdesc --- except that we
441 * may stuff new names into it below, so drop any rowtype label.
442 */
443 if (scanstate->simple)
444 {
445 scan_tupdesc = CreateTupleDescCopy(scanstate->funcstates[0].tupdesc);
446 scan_tupdesc->tdtypeid = RECORDOID;
447 scan_tupdesc->tdtypmod = -1;
448 }
449 else
450 {
451 AttrNumber attno = 0;
452
453 if (node->funcordinality)
454 natts++;
455
456 scan_tupdesc = CreateTemplateTupleDesc(natts, false);
457
458 for (i = 0; i < nfuncs; i++)
459 {
460 TupleDesc tupdesc = scanstate->funcstates[i].tupdesc;
461 int colcount = scanstate->funcstates[i].colcount;
462 int j;
463
464 for (j = 1; j <= colcount; j++)
465 TupleDescCopyEntry(scan_tupdesc, ++attno, tupdesc, j);
466 }
467
468 /* If doing ordinality, add a column of type "bigint" at the end */
469 if (node->funcordinality)
470 {
471 TupleDescInitEntry(scan_tupdesc,
472 ++attno,
473 NULL, /* don't care about the name here */
474 INT8OID,
475 -1,
476 0);
477 }
478
479 Assert(attno == natts);
480 }
481
482 /*
483 * Initialize scan slot and type.
484 */
485 ExecInitScanTupleSlot(estate, &scanstate->ss, scan_tupdesc);
486
487 /*
488 * Initialize result slot, type and projection.
489 */
490 ExecInitResultTupleSlotTL(estate, &scanstate->ss.ps);
491 ExecAssignScanProjectionInfo(&scanstate->ss);
492
493 /*
494 * initialize child expressions
495 */
496 scanstate->ss.ps.qual =
497 ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
498
499 /*
500 * Create a memory context that ExecMakeTableFunctionResult can use to
501 * evaluate function arguments in. We can't use the per-tuple context for
502 * this because it gets reset too often; but we don't want to leak
503 * evaluation results into the query-lifespan context either. We just
504 * need one context, because we evaluate each function separately.
505 */
506 scanstate->argcontext = AllocSetContextCreate(CurrentMemoryContext,
507 "Table function arguments",
508 ALLOCSET_DEFAULT_SIZES);
509
510 return scanstate;
511 }
512
513 /* ----------------------------------------------------------------
514 * ExecEndFunctionScan
515 *
516 * frees any storage allocated through C routines.
517 * ----------------------------------------------------------------
518 */
519 void
ExecEndFunctionScan(FunctionScanState * node)520 ExecEndFunctionScan(FunctionScanState *node)
521 {
522 int i;
523
524 /*
525 * Free the exprcontext
526 */
527 ExecFreeExprContext(&node->ss.ps);
528
529 /*
530 * clean out the tuple table
531 */
532 ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
533 ExecClearTuple(node->ss.ss_ScanTupleSlot);
534
535 /*
536 * Release slots and tuplestore resources
537 */
538 for (i = 0; i < node->nfuncs; i++)
539 {
540 FunctionScanPerFuncState *fs = &node->funcstates[i];
541
542 if (fs->func_slot)
543 ExecClearTuple(fs->func_slot);
544
545 if (fs->tstore != NULL)
546 {
547 tuplestore_end(node->funcstates[i].tstore);
548 fs->tstore = NULL;
549 }
550 }
551 }
552
553 /* ----------------------------------------------------------------
554 * ExecReScanFunctionScan
555 *
556 * Rescans the relation.
557 * ----------------------------------------------------------------
558 */
559 void
ExecReScanFunctionScan(FunctionScanState * node)560 ExecReScanFunctionScan(FunctionScanState *node)
561 {
562 FunctionScan *scan = (FunctionScan *) node->ss.ps.plan;
563 int i;
564 Bitmapset *chgparam = node->ss.ps.chgParam;
565
566 ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
567 for (i = 0; i < node->nfuncs; i++)
568 {
569 FunctionScanPerFuncState *fs = &node->funcstates[i];
570
571 if (fs->func_slot)
572 ExecClearTuple(fs->func_slot);
573 }
574
575 ExecScanReScan(&node->ss);
576
577 /*
578 * Here we have a choice whether to drop the tuplestores (and recompute
579 * the function outputs) or just rescan them. We must recompute if an
580 * expression contains changed parameters, else we rescan.
581 *
582 * XXX maybe we should recompute if the function is volatile? But in
583 * general the executor doesn't conditionalize its actions on that.
584 */
585 if (chgparam)
586 {
587 ListCell *lc;
588
589 i = 0;
590 foreach(lc, scan->functions)
591 {
592 RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
593
594 if (bms_overlap(chgparam, rtfunc->funcparams))
595 {
596 if (node->funcstates[i].tstore != NULL)
597 {
598 tuplestore_end(node->funcstates[i].tstore);
599 node->funcstates[i].tstore = NULL;
600 }
601 node->funcstates[i].rowcount = -1;
602 }
603 i++;
604 }
605 }
606
607 /* Reset ordinality counter */
608 node->ordinal = 0;
609
610 /* Make sure we rewind any remaining tuplestores */
611 for (i = 0; i < node->nfuncs; i++)
612 {
613 if (node->funcstates[i].tstore != NULL)
614 tuplestore_rescan(node->funcstates[i].tstore);
615 }
616 }
617