Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * tidpath.c
4 : * Routines to determine which TID conditions are usable for scanning
5 : * a given relation, and create TidPaths and TidRangePaths accordingly.
6 : *
7 : * For TidPaths, we look for WHERE conditions of the form
8 : * "CTID = pseudoconstant", which can be implemented by just fetching
9 : * the tuple directly via heap_fetch(). We can also handle OR'd conditions
10 : * such as (CTID = const1) OR (CTID = const2), as well as ScalarArrayOpExpr
11 : * conditions of the form CTID = ANY(pseudoconstant_array). In particular
12 : * this allows
13 : * WHERE ctid IN (tid1, tid2, ...)
14 : *
15 : * As with indexscans, our definition of "pseudoconstant" is pretty liberal:
16 : * we allow anything that doesn't involve a volatile function or a Var of
17 : * the relation under consideration. Vars belonging to other relations of
18 : * the query are allowed, giving rise to parameterized TID scans.
19 : *
20 : * We also support "WHERE CURRENT OF cursor" conditions (CurrentOfExpr),
21 : * which amount to "CTID = run-time-determined-TID". These could in
22 : * theory be translated to a simple comparison of CTID to the result of
23 : * a function, but in practice it works better to keep the special node
24 : * representation all the way through to execution.
25 : *
26 : * Additionally, TidRangePaths may be created for conditions of the form
27 : * "CTID relop pseudoconstant", where relop is one of >,>=,<,<=, and
28 : * AND-clauses composed of such conditions.
29 : *
30 : * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
31 : * Portions Copyright (c) 1994, Regents of the University of California
32 : *
33 : *
34 : * IDENTIFICATION
35 : * src/backend/optimizer/path/tidpath.c
36 : *
37 : *-------------------------------------------------------------------------
38 : */
39 : #include "postgres.h"
40 :
41 : #include "access/sysattr.h"
42 : #include "catalog/pg_operator.h"
43 : #include "catalog/pg_type.h"
44 : #include "nodes/nodeFuncs.h"
45 : #include "optimizer/optimizer.h"
46 : #include "optimizer/pathnode.h"
47 : #include "optimizer/paths.h"
48 : #include "optimizer/restrictinfo.h"
49 :
50 :
51 : /*
52 : * Does this Var represent the CTID column of the specified baserel?
53 : */
54 : static inline bool
55 793330 : IsCTIDVar(Var *var, RelOptInfo *rel)
56 : {
57 : /* The vartype check is strictly paranoia */
58 793330 : if (var->varattno == SelfItemPointerAttributeNumber &&
59 1438 : var->vartype == TIDOID &&
60 1438 : var->varno == rel->relid &&
61 1318 : var->varnullingrels == NULL &&
62 1318 : var->varlevelsup == 0)
63 1318 : return true;
64 792012 : return false;
65 : }
66 :
67 : /*
68 : * Check to see if a RestrictInfo is of the form
69 : * CTID OP pseudoconstant
70 : * or
71 : * pseudoconstant OP CTID
72 : * where OP is a binary operation, the CTID Var belongs to relation "rel",
73 : * and nothing on the other side of the clause does.
74 : */
75 : static bool
76 784086 : IsBinaryTidClause(RestrictInfo *rinfo, RelOptInfo *rel)
77 : {
78 : OpExpr *node;
79 : Node *arg1,
80 : *arg2,
81 : *other;
82 : Relids other_relids;
83 :
84 : /* Must be an OpExpr */
85 784086 : if (!is_opclause(rinfo->clause))
86 156000 : return false;
87 628086 : node = (OpExpr *) rinfo->clause;
88 :
89 : /* OpExpr must have two arguments */
90 628086 : if (list_length(node->args) != 2)
91 48 : return false;
92 628038 : arg1 = linitial(node->args);
93 628038 : arg2 = lsecond(node->args);
94 :
95 : /* Look for CTID as either argument */
96 628038 : other = NULL;
97 628038 : other_relids = NULL;
98 1226092 : if (arg1 && IsA(arg1, Var) &&
99 598054 : IsCTIDVar((Var *) arg1, rel))
100 : {
101 928 : other = arg2;
102 928 : other_relids = rinfo->right_relids;
103 : }
104 732004 : if (!other && arg2 && IsA(arg2, Var) &&
105 103966 : IsCTIDVar((Var *) arg2, rel))
106 : {
107 228 : other = arg1;
108 228 : other_relids = rinfo->left_relids;
109 : }
110 628038 : if (!other)
111 626882 : return false;
112 :
113 : /* The other argument must be a pseudoconstant */
114 2312 : if (bms_is_member(rel->relid, other_relids) ||
115 1156 : contain_volatile_functions(other))
116 0 : return false;
117 :
118 1156 : return true; /* success */
119 : }
120 :
121 : /*
122 : * Check to see if a RestrictInfo is of the form
123 : * CTID = pseudoconstant
124 : * or
125 : * pseudoconstant = CTID
126 : * where the CTID Var belongs to relation "rel", and nothing on the
127 : * other side of the clause does.
128 : */
129 : static bool
130 442166 : IsTidEqualClause(RestrictInfo *rinfo, RelOptInfo *rel)
131 : {
132 442166 : if (!IsBinaryTidClause(rinfo, rel))
133 441420 : return false;
134 :
135 746 : if (((OpExpr *) rinfo->clause)->opno == TIDEqualOperator)
136 370 : return true;
137 :
138 376 : return false;
139 : }
140 :
141 : /*
142 : * Check to see if a RestrictInfo is of the form
143 : * CTID OP pseudoconstant
144 : * or
145 : * pseudoconstant OP CTID
146 : * where OP is a range operator such as <, <=, >, or >=, the CTID Var belongs
147 : * to relation "rel", and nothing on the other side of the clause does.
148 : */
149 : static bool
150 341920 : IsTidRangeClause(RestrictInfo *rinfo, RelOptInfo *rel)
151 : {
152 : Oid opno;
153 :
154 341920 : if (!IsBinaryTidClause(rinfo, rel))
155 341510 : return false;
156 410 : opno = ((OpExpr *) rinfo->clause)->opno;
157 :
158 410 : if (opno == TIDLessOperator || opno == TIDLessEqOperator ||
159 232 : opno == TIDGreaterOperator || opno == TIDGreaterEqOperator)
160 232 : return true;
161 :
162 178 : return false;
163 : }
164 :
165 : /*
166 : * Check to see if a RestrictInfo is of the form
167 : * CTID = ANY (pseudoconstant_array)
168 : * where the CTID Var belongs to relation "rel", and nothing on the
169 : * other side of the clause does.
170 : */
171 : static bool
172 335088 : IsTidEqualAnyClause(PlannerInfo *root, RestrictInfo *rinfo, RelOptInfo *rel)
173 : {
174 : ScalarArrayOpExpr *node;
175 : Node *arg1,
176 : *arg2;
177 :
178 : /* Must be a ScalarArrayOpExpr */
179 335088 : if (!(rinfo->clause && IsA(rinfo->clause, ScalarArrayOpExpr)))
180 320446 : return false;
181 14642 : node = (ScalarArrayOpExpr *) rinfo->clause;
182 :
183 : /* Operator must be tideq */
184 14642 : if (node->opno != TIDEqualOperator)
185 14612 : return false;
186 30 : if (!node->useOr)
187 0 : return false;
188 : Assert(list_length(node->args) == 2);
189 30 : arg1 = linitial(node->args);
190 30 : arg2 = lsecond(node->args);
191 :
192 : /* CTID must be first argument */
193 60 : if (arg1 && IsA(arg1, Var) &&
194 30 : IsCTIDVar((Var *) arg1, rel))
195 : {
196 : /* The other argument must be a pseudoconstant */
197 60 : if (bms_is_member(rel->relid, pull_varnos(root, arg2)) ||
198 30 : contain_volatile_functions(arg2))
199 0 : return false;
200 :
201 30 : return true; /* success */
202 : }
203 :
204 0 : return false;
205 : }
206 :
207 : /*
208 : * Check to see if a RestrictInfo is a CurrentOfExpr referencing "rel".
209 : */
210 : static bool
211 335058 : IsCurrentOfClause(RestrictInfo *rinfo, RelOptInfo *rel)
212 : {
213 : CurrentOfExpr *node;
214 :
215 : /* Must be a CurrentOfExpr */
216 335058 : if (!(rinfo->clause && IsA(rinfo->clause, CurrentOfExpr)))
217 334666 : return false;
218 392 : node = (CurrentOfExpr *) rinfo->clause;
219 :
220 : /* If it references this rel, we're good */
221 392 : if (node->cvarno == rel->relid)
222 392 : return true;
223 :
224 0 : return false;
225 : }
226 :
227 : /*
228 : * Extract a set of CTID conditions from the given RestrictInfo
229 : *
230 : * Returns a List of CTID qual RestrictInfos for the specified rel (with
231 : * implicit OR semantics across the list), or NIL if there are no usable
232 : * conditions.
233 : *
234 : * This function considers only base cases; AND/OR combination is handled
235 : * below. Therefore the returned List never has more than one element.
236 : * (Using a List may seem a bit weird, but it simplifies the caller.)
237 : */
238 : static List *
239 342784 : TidQualFromRestrictInfo(PlannerInfo *root, RestrictInfo *rinfo, RelOptInfo *rel)
240 : {
241 : /*
242 : * We may ignore pseudoconstant clauses (they can't contain Vars, so could
243 : * not match anyway).
244 : */
245 342784 : if (rinfo->pseudoconstant)
246 5896 : return NIL;
247 :
248 : /*
249 : * If clause must wait till after some lower-security-level restriction
250 : * clause, reject it.
251 : */
252 336888 : if (!restriction_is_securely_promotable(rinfo, rel))
253 1586 : return NIL;
254 :
255 : /*
256 : * Check all base cases. If we get a match, return the clause.
257 : */
258 670390 : if (IsTidEqualClause(rinfo, rel) ||
259 670146 : IsTidEqualAnyClause(root, rinfo, rel) ||
260 335058 : IsCurrentOfClause(rinfo, rel))
261 636 : return list_make1(rinfo);
262 :
263 334666 : return NIL;
264 : }
265 :
266 : /*
267 : * Extract a set of CTID conditions from implicit-AND List of RestrictInfos
268 : *
269 : * Returns a List of CTID qual RestrictInfos for the specified rel (with
270 : * implicit OR semantics across the list), or NIL if there are no usable
271 : * equality conditions.
272 : *
273 : * This function is just concerned with handling AND/OR recursion.
274 : */
275 : static List *
276 349306 : TidQualFromRestrictInfoList(PlannerInfo *root, List *rlist, RelOptInfo *rel)
277 : {
278 349306 : List *rlst = NIL;
279 : ListCell *l;
280 :
281 692130 : foreach(l, rlist)
282 : {
283 343460 : RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
284 :
285 343460 : if (restriction_is_or_clause(rinfo))
286 : {
287 : ListCell *j;
288 :
289 : /*
290 : * We must be able to extract a CTID condition from every
291 : * sub-clause of an OR, or we can't use it.
292 : */
293 3658 : foreach(j, ((BoolExpr *) rinfo->orclause)->args)
294 : {
295 3634 : Node *orarg = (Node *) lfirst(j);
296 : List *sublist;
297 :
298 : /* OR arguments should be ANDs or sub-RestrictInfos */
299 3634 : if (is_andclause(orarg))
300 : {
301 700 : List *andargs = ((BoolExpr *) orarg)->args;
302 :
303 : /* Recurse in case there are sub-ORs */
304 700 : sublist = TidQualFromRestrictInfoList(root, andargs, rel);
305 : }
306 : else
307 : {
308 2934 : RestrictInfo *ri = castNode(RestrictInfo, orarg);
309 :
310 : Assert(!restriction_is_or_clause(ri));
311 2934 : sublist = TidQualFromRestrictInfo(root, ri, rel);
312 : }
313 :
314 : /*
315 : * If nothing found in this arm, we can't do anything with
316 : * this OR clause.
317 : */
318 3634 : if (sublist == NIL)
319 : {
320 3586 : rlst = NIL; /* forget anything we had */
321 3586 : break; /* out of loop over OR args */
322 : }
323 :
324 : /*
325 : * OK, continue constructing implicitly-OR'ed result list.
326 : */
327 48 : rlst = list_concat(rlst, sublist);
328 : }
329 : }
330 : else
331 : {
332 : /* Not an OR clause, so handle base cases */
333 339850 : rlst = TidQualFromRestrictInfo(root, rinfo, rel);
334 : }
335 :
336 : /*
337 : * Stop as soon as we find any usable CTID condition. In theory we
338 : * could get CTID equality conditions from different AND'ed clauses,
339 : * in which case we could try to pick the most efficient one. In
340 : * practice, such usage seems very unlikely, so we don't bother; we
341 : * just exit as soon as we find the first candidate.
342 : */
343 343460 : if (rlst)
344 636 : break;
345 : }
346 :
347 349306 : return rlst;
348 : }
349 :
350 : /*
351 : * Extract a set of CTID range conditions from implicit-AND List of RestrictInfos
352 : *
353 : * Returns a List of CTID range qual RestrictInfos for the specified rel
354 : * (with implicit AND semantics across the list), or NIL if there are no
355 : * usable range conditions or if the rel's table AM does not support TID range
356 : * scans.
357 : */
358 : static List *
359 348606 : TidRangeQualFromRestrictInfoList(List *rlist, RelOptInfo *rel)
360 : {
361 348606 : List *rlst = NIL;
362 : ListCell *l;
363 :
364 348606 : if ((rel->amflags & AMFLAG_HAS_TID_RANGE) == 0)
365 0 : return NIL;
366 :
367 690526 : foreach(l, rlist)
368 : {
369 341920 : RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
370 :
371 341920 : if (IsTidRangeClause(rinfo, rel))
372 232 : rlst = lappend(rlst, rinfo);
373 : }
374 :
375 348606 : return rlst;
376 : }
377 :
378 : /*
379 : * Given a list of join clauses involving our rel, create a parameterized
380 : * TidPath for each one that is a suitable TidEqual clause.
381 : *
382 : * In principle we could combine clauses that reference the same outer rels,
383 : * but it doesn't seem like such cases would arise often enough to be worth
384 : * troubling over.
385 : */
386 : static void
387 454244 : BuildParameterizedTidPaths(PlannerInfo *root, RelOptInfo *rel, List *clauses)
388 : {
389 : ListCell *l;
390 :
391 569736 : foreach(l, clauses)
392 : {
393 115492 : RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
394 : List *tidquals;
395 : Relids required_outer;
396 :
397 : /*
398 : * Validate whether each clause is actually usable; we must check this
399 : * even when examining clauses generated from an EquivalenceClass,
400 : * since they might not satisfy the restriction on not having Vars of
401 : * our rel on the other side, or somebody might've built an operator
402 : * class that accepts type "tid" but has other operators in it.
403 : *
404 : * We currently consider only TidEqual join clauses. In principle we
405 : * might find a suitable ScalarArrayOpExpr in the rel's joininfo list,
406 : * but it seems unlikely to be worth expending the cycles to check.
407 : * And we definitely won't find a CurrentOfExpr here. Hence, we don't
408 : * use TidQualFromRestrictInfo; but this must match that function
409 : * otherwise.
410 : */
411 115492 : if (rinfo->pseudoconstant ||
412 106864 : !restriction_is_securely_promotable(rinfo, rel) ||
413 106864 : !IsTidEqualClause(rinfo, rel))
414 115348 : continue;
415 :
416 : /*
417 : * Check if clause can be moved to this rel; this is probably
418 : * redundant when considering EC-derived clauses, but we must check it
419 : * for "loose" join clauses.
420 : */
421 156 : if (!join_clause_is_movable_to(rinfo, rel))
422 12 : continue;
423 :
424 : /* OK, make list of clauses for this path */
425 144 : tidquals = list_make1(rinfo);
426 :
427 : /* Compute required outer rels for this path */
428 144 : required_outer = bms_union(rinfo->required_relids, rel->lateral_relids);
429 144 : required_outer = bms_del_member(required_outer, rel->relid);
430 :
431 144 : add_path(rel, (Path *) create_tidscan_path(root, rel, tidquals,
432 : required_outer));
433 : }
434 454244 : }
435 :
436 : /*
437 : * Test whether an EquivalenceClass member matches our rel's CTID Var.
438 : *
439 : * This is a callback for use by generate_implied_equalities_for_column.
440 : */
441 : static bool
442 94692 : ec_member_matches_ctid(PlannerInfo *root, RelOptInfo *rel,
443 : EquivalenceClass *ec, EquivalenceMember *em,
444 : void *arg)
445 : {
446 185972 : if (em->em_expr && IsA(em->em_expr, Var) &&
447 91280 : IsCTIDVar((Var *) em->em_expr, rel))
448 132 : return true;
449 94560 : return false;
450 : }
451 :
452 : /*
453 : * create_tidscan_paths
454 : * Create paths corresponding to direct TID scans of the given rel.
455 : *
456 : * Candidate paths are added to the rel's pathlist (using add_path).
457 : */
458 : void
459 348606 : create_tidscan_paths(PlannerInfo *root, RelOptInfo *rel)
460 : {
461 : List *tidquals;
462 : List *tidrangequals;
463 :
464 : /*
465 : * If any suitable quals exist in the rel's baserestrict list, generate a
466 : * plain (unparameterized) TidPath with them.
467 : */
468 348606 : tidquals = TidQualFromRestrictInfoList(root, rel->baserestrictinfo, rel);
469 :
470 348606 : if (tidquals != NIL)
471 : {
472 : /*
473 : * This path uses no join clauses, but it could still have required
474 : * parameterization due to LATERAL refs in its tlist.
475 : */
476 612 : Relids required_outer = rel->lateral_relids;
477 :
478 612 : add_path(rel, (Path *) create_tidscan_path(root, rel, tidquals,
479 : required_outer));
480 : }
481 :
482 : /*
483 : * If there are range quals in the baserestrict list, generate a
484 : * TidRangePath.
485 : */
486 348606 : tidrangequals = TidRangeQualFromRestrictInfoList(rel->baserestrictinfo,
487 : rel);
488 :
489 348606 : if (tidrangequals != NIL)
490 : {
491 : /*
492 : * This path uses no join clauses, but it could still have required
493 : * parameterization due to LATERAL refs in its tlist.
494 : */
495 202 : Relids required_outer = rel->lateral_relids;
496 :
497 202 : add_path(rel, (Path *) create_tidrangescan_path(root, rel,
498 : tidrangequals,
499 : required_outer));
500 : }
501 :
502 : /*
503 : * Try to generate parameterized TidPaths using equality clauses extracted
504 : * from EquivalenceClasses. (This is important since simple "t1.ctid =
505 : * t2.ctid" clauses will turn into ECs.)
506 : */
507 348606 : if (rel->has_eclass_joins)
508 : {
509 : List *clauses;
510 :
511 : /* Generate clauses, skipping any that join to lateral_referencers */
512 105638 : clauses = generate_implied_equalities_for_column(root,
513 : rel,
514 : ec_member_matches_ctid,
515 : NULL,
516 : rel->lateral_referencers);
517 :
518 : /* Generate a path for each usable join clause */
519 105638 : BuildParameterizedTidPaths(root, rel, clauses);
520 : }
521 :
522 : /*
523 : * Also consider parameterized TidPaths using "loose" join quals. Quals
524 : * of the form "t1.ctid = t2.ctid" would turn into these if they are outer
525 : * join quals, for example.
526 : */
527 348606 : BuildParameterizedTidPaths(root, rel, rel->joininfo);
528 348606 : }
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