Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * pgpa_join.c
4 : * analysis of joins in Plan trees
5 : *
6 : * Copyright (c) 2016-2026, PostgreSQL Global Development Group
7 : *
8 : * contrib/pg_plan_advice/pgpa_join.c
9 : *
10 : *-------------------------------------------------------------------------
11 : */
12 :
13 : #include "postgres.h"
14 :
15 : #include "pgpa_join.h"
16 : #include "pgpa_scan.h"
17 : #include "pgpa_walker.h"
18 :
19 : #include "nodes/pathnodes.h"
20 : #include "nodes/print.h"
21 : #include "parser/parsetree.h"
22 :
23 : /*
24 : * Temporary object used when unrolling a join tree.
25 : */
26 : struct pgpa_join_unroller
27 : {
28 : unsigned nallocated;
29 : unsigned nused;
30 : Plan *outer_subplan;
31 : ElidedNode *outer_elided_node;
32 : bool outer_beneath_any_gather;
33 : pgpa_join_strategy *strategy;
34 : Plan **inner_subplans;
35 : ElidedNode **inner_elided_nodes;
36 : pgpa_join_unroller **inner_unrollers;
37 : bool *inner_beneath_any_gather;
38 : };
39 :
40 : static pgpa_join_strategy pgpa_decompose_join(pgpa_plan_walker_context *walker,
41 : Plan *plan,
42 : Plan **realouter,
43 : Plan **realinner,
44 : ElidedNode **elidedrealouter,
45 : ElidedNode **elidedrealinner,
46 : bool *found_any_outer_gather,
47 : bool *found_any_inner_gather);
48 : static ElidedNode *pgpa_descend_node(PlannedStmt *pstmt, Plan **plan);
49 : static ElidedNode *pgpa_descend_any_gather(PlannedStmt *pstmt, Plan **plan,
50 : bool *found_any_gather);
51 : static bool pgpa_descend_any_unique(PlannedStmt *pstmt, Plan **plan,
52 : ElidedNode **elided_node);
53 :
54 : static bool is_result_node_with_child(Plan *plan);
55 : static bool is_sorting_plan(Plan *plan);
56 :
57 : /*
58 : * Create an initially-empty object for unrolling joins.
59 : *
60 : * This function creates a helper object that can later be used to create a
61 : * pgpa_unrolled_join, after first calling pgpa_unroll_join one or more times.
62 : */
63 : pgpa_join_unroller *
64 87 : pgpa_create_join_unroller(void)
65 : {
66 : pgpa_join_unroller *join_unroller;
67 :
68 87 : join_unroller = palloc0_object(pgpa_join_unroller);
69 87 : join_unroller->nallocated = 4;
70 87 : join_unroller->strategy =
71 87 : palloc_array(pgpa_join_strategy, join_unroller->nallocated);
72 87 : join_unroller->inner_subplans =
73 87 : palloc_array(Plan *, join_unroller->nallocated);
74 87 : join_unroller->inner_elided_nodes =
75 87 : palloc_array(ElidedNode *, join_unroller->nallocated);
76 87 : join_unroller->inner_unrollers =
77 87 : palloc_array(pgpa_join_unroller *, join_unroller->nallocated);
78 87 : join_unroller->inner_beneath_any_gather =
79 87 : palloc_array(bool, join_unroller->nallocated);
80 :
81 87 : return join_unroller;
82 : }
83 :
84 : /*
85 : * Unroll one level of an unrollable join tree.
86 : *
87 : * Our basic goal here is to unroll join trees as they occur in the Plan
88 : * tree into a simpler and more regular structure that we can more easily
89 : * use for further processing. Unrolling is outer-deep, so if the plan tree
90 : * has Join1(Join2(A,B),Join3(C,D)), the same join unroller object should be
91 : * used for Join1 and Join2, but a different one will be needed for Join3,
92 : * since that involves a join within the *inner* side of another join.
93 : *
94 : * pgpa_plan_walker creates a "top level" join unroller object when it
95 : * encounters a join in a portion of the plan tree in which no join unroller
96 : * is already active. From there, this function is responsible for determing
97 : * to what portion of the plan tree that join unroller applies, and for
98 : * creating any subordinate join unroller objects that are needed as a result
99 : * of non-outer-deep join trees. We do this by returning the join unroller
100 : * objects that should be used for further traversal of the outer and inner
101 : * subtrees of the current plan node via *outer_join_unroller and
102 : * *inner_join_unroller, respectively.
103 : */
104 : void
105 120 : pgpa_unroll_join(pgpa_plan_walker_context *walker, Plan *plan,
106 : bool beneath_any_gather,
107 : pgpa_join_unroller *join_unroller,
108 : pgpa_join_unroller **outer_join_unroller,
109 : pgpa_join_unroller **inner_join_unroller)
110 : {
111 : pgpa_join_strategy strategy;
112 : Plan *realinner,
113 : *realouter;
114 : ElidedNode *elidedinner,
115 : *elidedouter;
116 : int n;
117 120 : bool found_any_outer_gather = false;
118 120 : bool found_any_inner_gather = false;
119 :
120 : Assert(join_unroller != NULL);
121 :
122 : /*
123 : * We need to pass the join_unroller object down through certain types of
124 : * plan nodes -- anything that's considered part of the join strategy, and
125 : * any other nodes that can occur in a join tree despite not being scans
126 : * or joins.
127 : *
128 : * This includes:
129 : *
130 : * (1) Materialize, Memoize, and Hash nodes, which are part of the join
131 : * strategy,
132 : *
133 : * (2) Gather and Gather Merge nodes, which can occur at any point in the
134 : * join tree where the planner decided to initiate parallelism,
135 : *
136 : * (3) Sort and IncrementalSort nodes, which can occur beneath MergeJoin
137 : * or GatherMerge,
138 : *
139 : * (4) Agg and Unique nodes, which can occur when we decide to make the
140 : * nullable side of a semijoin unique and then join the result, and
141 : *
142 : * (5) Result nodes with children, which can be added either to project to
143 : * enforce a one-time filter (but Result nodes without children are
144 : * degenerate scans or joins).
145 : */
146 120 : if (IsA(plan, Material) || IsA(plan, Memoize) || IsA(plan, Hash)
147 116 : || IsA(plan, Gather) || IsA(plan, GatherMerge)
148 116 : || is_sorting_plan(plan) || IsA(plan, Agg) || IsA(plan, Unique)
149 116 : || is_result_node_with_child(plan))
150 : {
151 4 : *outer_join_unroller = join_unroller;
152 4 : return;
153 : }
154 :
155 : /*
156 : * Since we've already handled nodes that require pass-through treatment,
157 : * this should be an unrollable join.
158 : */
159 116 : strategy = pgpa_decompose_join(walker, plan,
160 : &realouter, &realinner,
161 : &elidedouter, &elidedinner,
162 : &found_any_outer_gather,
163 : &found_any_inner_gather);
164 :
165 : /* If our workspace is full, expand it. */
166 116 : if (join_unroller->nused >= join_unroller->nallocated)
167 : {
168 0 : join_unroller->nallocated *= 2;
169 0 : join_unroller->strategy =
170 0 : repalloc_array(join_unroller->strategy,
171 : pgpa_join_strategy,
172 : join_unroller->nallocated);
173 0 : join_unroller->inner_subplans =
174 0 : repalloc_array(join_unroller->inner_subplans,
175 : Plan *,
176 : join_unroller->nallocated);
177 0 : join_unroller->inner_elided_nodes =
178 0 : repalloc_array(join_unroller->inner_elided_nodes,
179 : ElidedNode *,
180 : join_unroller->nallocated);
181 0 : join_unroller->inner_beneath_any_gather =
182 0 : repalloc_array(join_unroller->inner_beneath_any_gather,
183 : bool,
184 : join_unroller->nallocated);
185 0 : join_unroller->inner_unrollers =
186 0 : repalloc_array(join_unroller->inner_unrollers,
187 : pgpa_join_unroller *,
188 : join_unroller->nallocated);
189 : }
190 :
191 : /*
192 : * Since we're flattening outer-deep join trees, it follows that if the
193 : * outer side is still an unrollable join, it should be unrolled into this
194 : * same object. Otherwise, we've reached the limit of what we can unroll
195 : * into this object and must remember the outer side as the final outer
196 : * subplan.
197 : */
198 116 : if (elidedouter == NULL && pgpa_is_join(realouter))
199 29 : *outer_join_unroller = join_unroller;
200 : else
201 : {
202 87 : join_unroller->outer_subplan = realouter;
203 87 : join_unroller->outer_elided_node = elidedouter;
204 87 : join_unroller->outer_beneath_any_gather =
205 87 : beneath_any_gather || found_any_outer_gather;
206 : }
207 :
208 : /*
209 : * Store the inner subplan. If it's an unrollable join, it needs to be
210 : * flattened in turn, but into a new unroller object, not this one.
211 : */
212 116 : n = join_unroller->nused++;
213 116 : join_unroller->strategy[n] = strategy;
214 116 : join_unroller->inner_subplans[n] = realinner;
215 116 : join_unroller->inner_elided_nodes[n] = elidedinner;
216 116 : join_unroller->inner_beneath_any_gather[n] =
217 116 : beneath_any_gather || found_any_inner_gather;
218 116 : if (elidedinner == NULL && pgpa_is_join(realinner))
219 4 : *inner_join_unroller = pgpa_create_join_unroller();
220 : else
221 112 : *inner_join_unroller = NULL;
222 116 : join_unroller->inner_unrollers[n] = *inner_join_unroller;
223 : }
224 :
225 : /*
226 : * Use the data we've accumulated in a pgpa_join_unroller object to construct
227 : * a pgpa_unrolled_join.
228 : */
229 : pgpa_unrolled_join *
230 87 : pgpa_build_unrolled_join(pgpa_plan_walker_context *walker,
231 : pgpa_join_unroller *join_unroller)
232 : {
233 : pgpa_unrolled_join *ujoin;
234 : int i;
235 :
236 : /*
237 : * We shouldn't have gone even so far as to create a join unroller unless
238 : * we found at least one unrollable join.
239 : */
240 : Assert(join_unroller->nused > 0);
241 :
242 : /* Allocate result structures. */
243 87 : ujoin = palloc0_object(pgpa_unrolled_join);
244 87 : ujoin->ninner = join_unroller->nused;
245 87 : ujoin->strategy = palloc0_array(pgpa_join_strategy, join_unroller->nused);
246 87 : ujoin->inner = palloc0_array(pgpa_join_member, join_unroller->nused);
247 :
248 : /* Handle the outermost join. */
249 87 : ujoin->outer.plan = join_unroller->outer_subplan;
250 87 : ujoin->outer.elided_node = join_unroller->outer_elided_node;
251 87 : ujoin->outer.scan =
252 87 : pgpa_build_scan(walker, ujoin->outer.plan,
253 : ujoin->outer.elided_node,
254 87 : join_unroller->outer_beneath_any_gather,
255 : true);
256 :
257 : /*
258 : * We want the joins from the deepest part of the plan tree to appear
259 : * first in the result object, but the join unroller adds them in exactly
260 : * the reverse of that order, so we need to flip the order of the arrays
261 : * when constructing the final result.
262 : */
263 203 : for (i = 0; i < join_unroller->nused; ++i)
264 : {
265 116 : int k = join_unroller->nused - i - 1;
266 :
267 : /* Copy strategy, Plan, and ElidedNode. */
268 116 : ujoin->strategy[i] = join_unroller->strategy[k];
269 116 : ujoin->inner[i].plan = join_unroller->inner_subplans[k];
270 116 : ujoin->inner[i].elided_node = join_unroller->inner_elided_nodes[k];
271 :
272 : /*
273 : * Fill in remaining details, using either the nested join unroller,
274 : * or by deriving them from the plan and elided nodes.
275 : */
276 116 : if (join_unroller->inner_unrollers[k] != NULL)
277 4 : ujoin->inner[i].unrolled_join =
278 4 : pgpa_build_unrolled_join(walker,
279 4 : join_unroller->inner_unrollers[k]);
280 : else
281 112 : ujoin->inner[i].scan =
282 112 : pgpa_build_scan(walker, ujoin->inner[i].plan,
283 112 : ujoin->inner[i].elided_node,
284 112 : join_unroller->inner_beneath_any_gather[k],
285 : true);
286 : }
287 :
288 87 : return ujoin;
289 : }
290 :
291 : /*
292 : * Free memory allocated for pgpa_join_unroller.
293 : */
294 : void
295 83 : pgpa_destroy_join_unroller(pgpa_join_unroller *join_unroller)
296 : {
297 83 : pfree(join_unroller->strategy);
298 83 : pfree(join_unroller->inner_subplans);
299 83 : pfree(join_unroller->inner_elided_nodes);
300 83 : pfree(join_unroller->inner_unrollers);
301 83 : pfree(join_unroller->inner_beneath_any_gather);
302 83 : pfree(join_unroller);
303 83 : }
304 :
305 : /*
306 : * Identify the join strategy used by a join and the "real" inner and outer
307 : * plans.
308 : *
309 : * For example, a Hash Join always has a Hash node on the inner side, but
310 : * for all intents and purposes the real inner input is the Hash node's child,
311 : * not the Hash node itself.
312 : *
313 : * Likewise, a Merge Join may have Sort node on the inner or outer side; if
314 : * it does, the real input to the join is the Sort node's child, not the
315 : * Sort node itself.
316 : *
317 : * In addition, with a Merge Join or a Nested Loop, the join planning code
318 : * may add additional nodes such as Materialize or Memoize. We regard these
319 : * as an aspect of the join strategy. As in the previous cases, the true input
320 : * to the join is the underlying node.
321 : *
322 : * However, if any involved child node previously had a now-elided node stacked
323 : * on top, then we can't "look through" that node -- indeed, what's going to be
324 : * relevant for our purposes is the ElidedNode on top of that plan node, rather
325 : * than the plan node itself.
326 : *
327 : * If there are multiple elided nodes, we want that one that would have been
328 : * uppermost in the plan tree prior to setrefs processing; we expect to find
329 : * that one last in the list of elided nodes.
330 : *
331 : * On return *realouter and *realinner will have been set to the real inner
332 : * and real outer plans that we identified, and *elidedrealouter and
333 : * *elidedrealinner to the last of any corresponding elided nodes.
334 : * Additionally, *found_any_outer_gather and *found_any_inner_gather will
335 : * be set to true if we looked through a Gather or Gather Merge node on
336 : * that side of the join, and false otherwise.
337 : */
338 : static pgpa_join_strategy
339 116 : pgpa_decompose_join(pgpa_plan_walker_context *walker, Plan *plan,
340 : Plan **realouter, Plan **realinner,
341 : ElidedNode **elidedrealouter, ElidedNode **elidedrealinner,
342 : bool *found_any_outer_gather, bool *found_any_inner_gather)
343 : {
344 116 : PlannedStmt *pstmt = walker->pstmt;
345 116 : JoinType jointype = ((Join *) plan)->jointype;
346 116 : Plan *outerplan = plan->lefttree;
347 116 : Plan *innerplan = plan->righttree;
348 : ElidedNode *elidedouter;
349 : ElidedNode *elidedinner;
350 : pgpa_join_strategy strategy;
351 : bool uniqueouter;
352 : bool uniqueinner;
353 :
354 116 : elidedouter = pgpa_last_elided_node(pstmt, outerplan);
355 116 : elidedinner = pgpa_last_elided_node(pstmt, innerplan);
356 116 : *found_any_outer_gather = false;
357 116 : *found_any_inner_gather = false;
358 :
359 116 : switch (nodeTag(plan))
360 : {
361 20 : case T_MergeJoin:
362 :
363 : /*
364 : * The planner may have chosen to place a Material node on the
365 : * inner side of the MergeJoin; if this is present, we record it
366 : * as part of the join strategy.
367 : */
368 20 : if (elidedinner == NULL && IsA(innerplan, Material))
369 : {
370 1 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
371 1 : strategy = JSTRAT_MERGE_JOIN_MATERIALIZE;
372 : }
373 : else
374 19 : strategy = JSTRAT_MERGE_JOIN_PLAIN;
375 :
376 : /*
377 : * For a MergeJoin, either the outer or the inner subplan, or
378 : * both, may have needed to be sorted; we must disregard any Sort
379 : * or IncrementalSort node to find the real inner or outer
380 : * subplan.
381 : */
382 20 : if (elidedouter == NULL && is_sorting_plan(outerplan))
383 9 : elidedouter = pgpa_descend_node(pstmt, &outerplan);
384 20 : if (elidedinner == NULL && is_sorting_plan(innerplan))
385 11 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
386 20 : break;
387 :
388 43 : case T_NestLoop:
389 :
390 : /*
391 : * The planner may have chosen to place a Material or Memoize node
392 : * on the inner side of the NestLoop; if this is present, we
393 : * record it as part of the join strategy.
394 : */
395 43 : if (elidedinner == NULL && IsA(innerplan, Material))
396 : {
397 11 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
398 11 : strategy = JSTRAT_NESTED_LOOP_MATERIALIZE;
399 : }
400 32 : else if (elidedinner == NULL && IsA(innerplan, Memoize))
401 : {
402 2 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
403 2 : strategy = JSTRAT_NESTED_LOOP_MEMOIZE;
404 : }
405 : else
406 30 : strategy = JSTRAT_NESTED_LOOP_PLAIN;
407 43 : break;
408 :
409 53 : case T_HashJoin:
410 :
411 : /*
412 : * The inner subplan of a HashJoin is always a Hash node; the real
413 : * inner subplan is the Hash node's child.
414 : */
415 : Assert(IsA(innerplan, Hash));
416 : Assert(elidedinner == NULL);
417 53 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
418 53 : strategy = JSTRAT_HASH_JOIN;
419 53 : break;
420 :
421 0 : default:
422 0 : elog(ERROR, "unrecognized node type: %d", (int) nodeTag(plan));
423 : }
424 :
425 : /*
426 : * The planner may have decided to implement a semijoin by first making
427 : * the nullable side of the plan unique, and then performing a normal join
428 : * against the result. Therefore, we might need to descend through a
429 : * unique node on either side of the plan.
430 : */
431 116 : uniqueouter = pgpa_descend_any_unique(pstmt, &outerplan, &elidedouter);
432 116 : uniqueinner = pgpa_descend_any_unique(pstmt, &innerplan, &elidedinner);
433 :
434 : /*
435 : * Can we see a Result node here, to project above a Gather? So far I've
436 : * found no example that behaves that way; rather, the Gather or Gather
437 : * Merge is made to project. Hence, don't test is_result_node_with_child()
438 : * at this point.
439 : */
440 :
441 : /*
442 : * The planner may have decided to parallelize part of the join tree, so
443 : * we could find a Gather or Gather Merge node here. Note that, if
444 : * present, this will appear below nodes we considered as part of the join
445 : * strategy, but we could find another uniqueness-enforcing node below the
446 : * Gather or Gather Merge, if present.
447 : */
448 116 : if (elidedouter == NULL)
449 : {
450 116 : elidedouter = pgpa_descend_any_gather(pstmt, &outerplan,
451 : found_any_outer_gather);
452 120 : if (*found_any_outer_gather &&
453 4 : pgpa_descend_any_unique(pstmt, &outerplan, &elidedouter))
454 0 : uniqueouter = true;
455 : }
456 116 : if (elidedinner == NULL)
457 : {
458 116 : elidedinner = pgpa_descend_any_gather(pstmt, &innerplan,
459 : found_any_inner_gather);
460 121 : if (*found_any_inner_gather &&
461 5 : pgpa_descend_any_unique(pstmt, &innerplan, &elidedinner))
462 0 : uniqueinner = true;
463 : }
464 :
465 : /*
466 : * It's possible that a Result node has been inserted either to project a
467 : * target list or to implement a one-time filter. If so, we can descend
468 : * through it. Note that a Result node without a child would be a
469 : * degenerate scan or join, and not something we could descend through.
470 : */
471 116 : if (elidedouter == NULL && is_result_node_with_child(outerplan))
472 0 : elidedouter = pgpa_descend_node(pstmt, &outerplan);
473 116 : if (elidedinner == NULL && is_result_node_with_child(innerplan))
474 0 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
475 :
476 : /*
477 : * If this is a semijoin that was converted to an inner join by making one
478 : * side or the other unique, make a note that the inner or outer subplan,
479 : * as appropriate, should be treated as a query plan feature when the main
480 : * tree traversal reaches it.
481 : *
482 : * Conversely, if the planner could have made one side of the join unique
483 : * and thereby converted it to an inner join, and chose not to do so, that
484 : * is also worth noting.
485 : *
486 : * NB: This code could appear slightly higher up in this function, but
487 : * none of the nodes through which we just descended should have
488 : * associated RTIs.
489 : *
490 : * NB: This seems like a somewhat hacky way of passing information up to
491 : * the main tree walk, but I don't currently have a better idea.
492 : */
493 116 : if (uniqueouter)
494 5 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_UNIQUE, outerplan);
495 111 : else if (jointype == JOIN_RIGHT_SEMI)
496 1 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_NON_UNIQUE, outerplan);
497 116 : if (uniqueinner)
498 4 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_UNIQUE, innerplan);
499 112 : else if (jointype == JOIN_SEMI)
500 4 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_NON_UNIQUE, innerplan);
501 :
502 : /* Set output parameters. */
503 116 : *realouter = outerplan;
504 116 : *realinner = innerplan;
505 116 : *elidedrealouter = elidedouter;
506 116 : *elidedrealinner = elidedinner;
507 116 : return strategy;
508 : }
509 :
510 : /*
511 : * Descend through a Plan node in a join tree that the caller has determined
512 : * to be irrelevant.
513 : *
514 : * Updates *plan, and returns the last of any elided nodes pertaining to the
515 : * new plan node.
516 : */
517 : static ElidedNode *
518 110 : pgpa_descend_node(PlannedStmt *pstmt, Plan **plan)
519 : {
520 110 : *plan = (*plan)->lefttree;
521 110 : return pgpa_last_elided_node(pstmt, *plan);
522 : }
523 :
524 : /*
525 : * Descend through a Gather or Gather Merge node, if present, and any Sort
526 : * or IncrementalSort node occurring under a Gather Merge.
527 : *
528 : * Caller should have verified that there is no ElidedNode pertaining to
529 : * the initial value of *plan.
530 : *
531 : * Updates *plan, and returns the last of any elided nodes pertaining to the
532 : * new plan node. Sets *found_any_gather = true if either Gather or
533 : * Gather Merge was found, and otherwise leaves it unchanged.
534 : */
535 : static ElidedNode *
536 232 : pgpa_descend_any_gather(PlannedStmt *pstmt, Plan **plan,
537 : bool *found_any_gather)
538 : {
539 232 : if (IsA(*plan, Gather))
540 : {
541 4 : *found_any_gather = true;
542 4 : return pgpa_descend_node(pstmt, plan);
543 : }
544 :
545 228 : if (IsA(*plan, GatherMerge))
546 : {
547 5 : ElidedNode *elided = pgpa_descend_node(pstmt, plan);
548 :
549 5 : if (elided == NULL && is_sorting_plan(*plan))
550 5 : elided = pgpa_descend_node(pstmt, plan);
551 :
552 5 : *found_any_gather = true;
553 5 : return elided;
554 : }
555 :
556 223 : return NULL;
557 : }
558 :
559 : /*
560 : * If *plan is an Agg or Unique node, we want to descend through it, unless
561 : * it has a corresponding elided node. If its immediate child is a Sort or
562 : * IncrementalSort, we also want to descend through that, unless it has a
563 : * corresponding elided node.
564 : *
565 : * On entry, *elided_node must be the last of any elided nodes corresponding
566 : * to *plan; on exit, this will still be true, but *plan may have been updated.
567 : *
568 : * The reason we don't want to descend through elided nodes is that a single
569 : * join tree can't cross through any sort of elided node: subqueries are
570 : * planned separately, and planning inside an Append or MergeAppend is
571 : * separate from planning outside of it.
572 : *
573 : * The return value is true if we descend through a node that we believe is
574 : * making one side of a semijoin unique, and otherwise false.
575 : */
576 : static bool
577 241 : pgpa_descend_any_unique(PlannedStmt *pstmt, Plan **plan,
578 : ElidedNode **elided_node)
579 : {
580 241 : bool descend = false;
581 241 : bool sjunique = false;
582 :
583 241 : if (*elided_node != NULL)
584 0 : return sjunique;
585 :
586 241 : if (IsA(*plan, Unique))
587 : {
588 0 : descend = true;
589 0 : sjunique = true;
590 : }
591 241 : else if (IsA(*plan, Agg))
592 : {
593 : /*
594 : * If this is a simple Agg node, then assume it's here to implement
595 : * semijoin uniqueness. Otherwise, assume it's completing an eager
596 : * aggregation or partitionwise aggregation operation that began at a
597 : * higher level of the plan tree.
598 : *
599 : * (Note that when we're using an Agg node for uniqueness, there's no
600 : * need for any case other than AGGSPLIT_SIMPLE, because there's no
601 : * aggregated column being computed. However, the fact that
602 : * AGGSPLIT_SIMPLE is in use doesn't prove that this Agg is here for
603 : * the semijoin uniqueness. Maybe we should adjust an Agg node to
604 : * carry a "purpose" field so that code like this can be more certain
605 : * of its analysis.)
606 : */
607 9 : descend = true;
608 9 : sjunique = (((Agg *) *plan)->aggsplit == AGGSPLIT_SIMPLE);
609 : }
610 :
611 241 : if (descend)
612 : {
613 9 : *elided_node = pgpa_descend_node(pstmt, plan);
614 :
615 9 : if (*elided_node == NULL && is_sorting_plan(*plan))
616 0 : *elided_node = pgpa_descend_node(pstmt, plan);
617 : }
618 :
619 241 : return sjunique;
620 : }
621 :
622 : /*
623 : * Is this a Result node that has a child?
624 : */
625 : static bool
626 348 : is_result_node_with_child(Plan *plan)
627 : {
628 348 : return IsA(plan, Result) && plan->lefttree != NULL;
629 : }
630 :
631 : /*
632 : * Is this a Plan node whose purpose is to put the data in a certain order?
633 : */
634 : static bool
635 170 : is_sorting_plan(Plan *plan)
636 : {
637 170 : return IsA(plan, Sort) || IsA(plan, IncrementalSort);
638 : }
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