1/*-------------------------------------------------------------------------
2 *
3 * nodeFunctionscan.c
4 * Support routines for scanning RangeFunctions (functions in rangetable).
5 *
6 * Portions Copyright (c) 1996-2019, 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 */
36typedef 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
46static 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 */
59static TupleTableSlot *
60FunctionNext(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 */
249static bool
250FunctionRecheck(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 */
265static TupleTableSlot *
266ExecFunctionScan(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 */
279FunctionScanState *
280ExecInitFunctionScan(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);
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 &TTSOpsMinimalTuple);
429 }
430 else
431 fs->func_slot = NULL;
432
433 natts += colcount;
434 i++;
435 }
436
437 /*
438 * Create the combined TupleDesc
439 *
440 * If there is just one function without ordinality, the scan result
441 * tupdesc is the same as the function result tupdesc --- except that we
442 * may stuff new names into it below, so drop any rowtype label.
443 */
444 if (scanstate->simple)
445 {
446 scan_tupdesc = CreateTupleDescCopy(scanstate->funcstates[0].tupdesc);
447 scan_tupdesc->tdtypeid = RECORDOID;
448 scan_tupdesc->tdtypmod = -1;
449 }
450 else
451 {
452 AttrNumber attno = 0;
453
454 if (node->funcordinality)
455 natts++;
456
457 scan_tupdesc = CreateTemplateTupleDesc(natts);
458
459 for (i = 0; i < nfuncs; i++)
460 {
461 TupleDesc tupdesc = scanstate->funcstates[i].tupdesc;
462 int colcount = scanstate->funcstates[i].colcount;
463 int j;
464
465 for (j = 1; j <= colcount; j++)
466 TupleDescCopyEntry(scan_tupdesc, ++attno, tupdesc, j);
467 }
468
469 /* If doing ordinality, add a column of type "bigint" at the end */
470 if (node->funcordinality)
471 {
472 TupleDescInitEntry(scan_tupdesc,
473 ++attno,
474 NULL, /* don't care about the name here */
475 INT8OID,
476 -1,
477 0);
478 }
479
480 Assert(attno == natts);
481 }
482
483 /*
484 * Initialize scan slot and type.
485 */
486 ExecInitScanTupleSlot(estate, &scanstate->ss, scan_tupdesc,
487 &TTSOpsMinimalTuple);
488
489 /*
490 * Initialize result slot, type and projection.
491 */
492 ExecInitResultTypeTL(&scanstate->ss.ps);
493 ExecAssignScanProjectionInfo(&scanstate->ss);
494
495 /*
496 * initialize child expressions
497 */
498 scanstate->ss.ps.qual =
499 ExecInitQual(node->scan.plan.qual, (PlanState *) scanstate);
500
501 /*
502 * Create a memory context that ExecMakeTableFunctionResult can use to
503 * evaluate function arguments in. We can't use the per-tuple context for
504 * this because it gets reset too often; but we don't want to leak
505 * evaluation results into the query-lifespan context either. We just
506 * need one context, because we evaluate each function separately.
507 */
508 scanstate->argcontext = AllocSetContextCreate(CurrentMemoryContext,
509 "Table function arguments",
510 ALLOCSET_DEFAULT_SIZES);
511
512 return scanstate;
513}
514
515/* ----------------------------------------------------------------
516 * ExecEndFunctionScan
517 *
518 * frees any storage allocated through C routines.
519 * ----------------------------------------------------------------
520 */
521void
522ExecEndFunctionScan(FunctionScanState *node)
523{
524 int i;
525
526 /*
527 * Free the exprcontext
528 */
529 ExecFreeExprContext(&node->ss.ps);
530
531 /*
532 * clean out the tuple table
533 */
534 if (node->ss.ps.ps_ResultTupleSlot)
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 */
562void
563ExecReScanFunctionScan(FunctionScanState *node)
564{
565 FunctionScan *scan = (FunctionScan *) node->ss.ps.plan;
566 int i;
567 Bitmapset *chgparam = node->ss.ps.chgParam;
568
569 if (node->ss.ps.ps_ResultTupleSlot)
570 ExecClearTuple(node->ss.ps.ps_ResultTupleSlot);
571 for (i = 0; i < node->nfuncs; i++)
572 {
573 FunctionScanPerFuncState *fs = &node->funcstates[i];
574
575 if (fs->func_slot)
576 ExecClearTuple(fs->func_slot);
577 }
578
579 ExecScanReScan(&node->ss);
580
581 /*
582 * Here we have a choice whether to drop the tuplestores (and recompute
583 * the function outputs) or just rescan them. We must recompute if an
584 * expression contains changed parameters, else we rescan.
585 *
586 * XXX maybe we should recompute if the function is volatile? But in
587 * general the executor doesn't conditionalize its actions on that.
588 */
589 if (chgparam)
590 {
591 ListCell *lc;
592
593 i = 0;
594 foreach(lc, scan->functions)
595 {
596 RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
597
598 if (bms_overlap(chgparam, rtfunc->funcparams))
599 {
600 if (node->funcstates[i].tstore != NULL)
601 {
602 tuplestore_end(node->funcstates[i].tstore);
603 node->funcstates[i].tstore = NULL;
604 }
605 node->funcstates[i].rowcount = -1;
606 }
607 i++;
608 }
609 }
610
611 /* Reset ordinality counter */
612 node->ordinal = 0;
613
614 /* Make sure we rewind any remaining tuplestores */
615 for (i = 0; i < node->nfuncs; i++)
616 {
617 if (node->funcstates[i].tstore != NULL)
618 tuplestore_rescan(node->funcstates[i].tstore);
619 }
620}
621