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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * pgpa_join.c
4 : : * analysis of joins in Plan trees
5 : : *
6 : : * Copyright (c) 2016-2025, 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 : 10166 : pgpa_create_join_unroller(void)
65 : : {
66 : 10166 : pgpa_join_unroller *join_unroller;
67 : :
68 : 10166 : join_unroller = palloc0_object(pgpa_join_unroller);
69 : 10166 : join_unroller->nallocated = 4;
70 : 10166 : join_unroller->strategy =
71 : 10166 : palloc_array(pgpa_join_strategy, join_unroller->nallocated);
72 : 10166 : join_unroller->inner_subplans =
73 : 10166 : palloc_array(Plan *, join_unroller->nallocated);
74 : 10166 : join_unroller->inner_elided_nodes =
75 : 10166 : palloc_array(ElidedNode *, join_unroller->nallocated);
76 : 10166 : join_unroller->inner_unrollers =
77 : 10166 : palloc_array(pgpa_join_unroller *, join_unroller->nallocated);
78 : 10166 : join_unroller->inner_beneath_any_gather =
79 : 10166 : palloc_array(bool, join_unroller->nallocated);
80 : :
81 : 20332 : return join_unroller;
82 : 10166 : }
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 : 13297 : 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 : 13297 : pgpa_join_strategy strategy;
112 : 13297 : Plan *realinner,
113 : : *realouter;
114 : 13297 : ElidedNode *elidedinner,
115 : : *elidedouter;
116 : 13297 : int n;
117 : 13297 : bool found_any_outer_gather = false;
118 : 13297 : bool found_any_inner_gather = false;
119 : :
120 [ + - ]: 13297 : 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 [ + + + - ]: 13297 : if (IsA(plan, Material) || IsA(plan, Memoize) || IsA(plan, Hash)
147 [ + + + + ]: 13234 : || IsA(plan, Gather) || IsA(plan, GatherMerge)
148 [ + - + + : 13092 : || is_sorting_plan(plan) || IsA(plan, Agg) || IsA(plan, Unique)
+ + ]
149 [ + + + + ]: 12995 : || is_result_node_with_child(plan))
150 : : {
151 : 317 : *outer_join_unroller = join_unroller;
152 : 317 : 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 : 12980 : 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 [ + + ]: 12980 : if (join_unroller->nused >= join_unroller->nallocated)
167 : : {
168 : 26 : join_unroller->nallocated *= 2;
169 : 26 : join_unroller->strategy =
170 : 26 : repalloc_array(join_unroller->strategy,
171 : : pgpa_join_strategy,
172 : : join_unroller->nallocated);
173 : 26 : join_unroller->inner_subplans =
174 : 26 : repalloc_array(join_unroller->inner_subplans,
175 : : Plan *,
176 : : join_unroller->nallocated);
177 : 26 : join_unroller->inner_elided_nodes =
178 : 26 : repalloc_array(join_unroller->inner_elided_nodes,
179 : : ElidedNode *,
180 : : join_unroller->nallocated);
181 : 26 : join_unroller->inner_beneath_any_gather =
182 : 26 : repalloc_array(join_unroller->inner_beneath_any_gather,
183 : : bool,
184 : : join_unroller->nallocated);
185 : 26 : join_unroller->inner_unrollers =
186 : 26 : repalloc_array(join_unroller->inner_unrollers,
187 : : pgpa_join_unroller *,
188 : : join_unroller->nallocated);
189 : 26 : }
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 [ + + + + ]: 12980 : if (elidedouter == NULL && pgpa_is_join(realouter))
199 : 2814 : *outer_join_unroller = join_unroller;
200 : : else
201 : : {
202 : 10166 : join_unroller->outer_subplan = realouter;
203 : 10166 : join_unroller->outer_elided_node = elidedouter;
204 : 10166 : join_unroller->outer_beneath_any_gather =
205 [ + + ]: 10166 : 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 : 12980 : n = join_unroller->nused++;
213 : 12980 : join_unroller->strategy[n] = strategy;
214 : 12980 : join_unroller->inner_subplans[n] = realinner;
215 : 12980 : join_unroller->inner_elided_nodes[n] = elidedinner;
216 : 12980 : join_unroller->inner_beneath_any_gather[n] =
217 [ + + ]: 12980 : beneath_any_gather || found_any_inner_gather;
218 [ + + + + ]: 12980 : if (elidedinner == NULL && pgpa_is_join(realinner))
219 : 410 : *inner_join_unroller = pgpa_create_join_unroller();
220 : : else
221 : 12570 : *inner_join_unroller = NULL;
222 : 12980 : join_unroller->inner_unrollers[n] = *inner_join_unroller;
223 [ - + ]: 13297 : }
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 : 10166 : pgpa_build_unrolled_join(pgpa_plan_walker_context *walker,
231 : : pgpa_join_unroller *join_unroller)
232 : : {
233 : 10166 : pgpa_unrolled_join *ujoin;
234 : 10166 : 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 [ + - ]: 10166 : Assert(join_unroller->nused > 0);
241 : :
242 : : /* Allocate result structures. */
243 : 10166 : ujoin = palloc0_object(pgpa_unrolled_join);
244 : 10166 : ujoin->ninner = join_unroller->nused;
245 : 10166 : ujoin->strategy = palloc0_array(pgpa_join_strategy, join_unroller->nused);
246 : 10166 : ujoin->inner = palloc0_array(pgpa_join_member, join_unroller->nused);
247 : :
248 : : /* Handle the outermost join. */
249 : 10166 : ujoin->outer.plan = join_unroller->outer_subplan;
250 : 10166 : ujoin->outer.elided_node = join_unroller->outer_elided_node;
251 : 10166 : ujoin->outer.scan =
252 : 20332 : pgpa_build_scan(walker, ujoin->outer.plan,
253 : 10166 : ujoin->outer.elided_node,
254 : 10166 : 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 [ + + ]: 23146 : for (i = 0; i < join_unroller->nused; ++i)
264 : : {
265 : 12980 : int k = join_unroller->nused - i - 1;
266 : :
267 : : /* Copy strategy, Plan, and ElidedNode. */
268 : 12980 : ujoin->strategy[i] = join_unroller->strategy[k];
269 : 12980 : ujoin->inner[i].plan = join_unroller->inner_subplans[k];
270 : 12980 : 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 [ + + ]: 12980 : if (join_unroller->inner_unrollers[k] != NULL)
277 : 410 : ujoin->inner[i].unrolled_join =
278 : 820 : pgpa_build_unrolled_join(walker,
279 : 410 : join_unroller->inner_unrollers[k]);
280 : : else
281 : 12570 : ujoin->inner[i].scan =
282 : 25140 : pgpa_build_scan(walker, ujoin->inner[i].plan,
283 : 12570 : ujoin->inner[i].elided_node,
284 : 12570 : join_unroller->inner_beneath_any_gather[k],
285 : : true);
286 : 12980 : }
287 : :
288 : 20332 : return ujoin;
289 : 10166 : }
290 : :
291 : : /*
292 : : * Free memory allocated for pgpa_join_unroller.
293 : : */
294 : : void
295 : 9756 : pgpa_destroy_join_unroller(pgpa_join_unroller *join_unroller)
296 : : {
297 : 9756 : pfree(join_unroller->strategy);
298 : 9756 : pfree(join_unroller->inner_subplans);
299 : 9756 : pfree(join_unroller->inner_elided_nodes);
300 : 9756 : pfree(join_unroller->inner_unrollers);
301 : 9756 : pfree(join_unroller);
302 : 9756 : }
303 : :
304 : : /*
305 : : * Identify the join strategy used by a join and the "real" inner and outer
306 : : * plans.
307 : : *
308 : : * For example, a Hash Join always has a Hash node on the inner side, but
309 : : * for all intents and purposes the real inner input is the Hash node's child,
310 : : * not the Hash node itself.
311 : : *
312 : : * Likewise, a Merge Join may have Sort note on the inner or outer side; if
313 : : * it does, the real input to the join is the Sort node's child, not the
314 : : * Sort node itself.
315 : : *
316 : : * In addition, with a Merge Join or a Nested Loop, the join planning code
317 : : * may add additional nodes such as Materialize or Memoize. We regard these
318 : : * as an aspect of the join strategy. As in the previous cases, the true input
319 : : * to the join is the underlying node.
320 : : *
321 : : * However, if any involved child node previously had a now-elided node stacked
322 : : * on top, then we can't "look through" that node -- indeed, what's going to be
323 : : * relevant for our purposes is the ElidedNode on top of that plan node, rather
324 : : * than the plan node itself.
325 : : *
326 : : * If there are multiple elided nodes, we want that one that would have been
327 : : * uppermost in the plan tree prior to setrefs processing; we expect to find
328 : : * that one last in the list of elided nodes.
329 : : *
330 : : * On return *realouter and *realinner will have been set to the real inner
331 : : * and real outer plans that we identified, and *elidedrealouter and
332 : : * *elidedrealinner to the last of any correspoding elided nodes.
333 : : * Additionally, *found_any_outer_gather and *found_any_inner_gather will
334 : : * be set to true if we looked through a Gather or Gather Merge node on
335 : : * that side of the join, and false otherwise.
336 : : */
337 : : static pgpa_join_strategy
338 : 12980 : pgpa_decompose_join(pgpa_plan_walker_context *walker, Plan *plan,
339 : : Plan **realouter, Plan **realinner,
340 : : ElidedNode **elidedrealouter, ElidedNode **elidedrealinner,
341 : : bool *found_any_outer_gather, bool *found_any_inner_gather)
342 : : {
343 : 12980 : PlannedStmt *pstmt = walker->pstmt;
344 : 12980 : JoinType jointype = ((Join *) plan)->jointype;
345 : 12980 : Plan *outerplan = plan->lefttree;
346 : 12980 : Plan *innerplan = plan->righttree;
347 : 12980 : ElidedNode *elidedouter;
348 : 12980 : ElidedNode *elidedinner;
349 : 12980 : pgpa_join_strategy strategy;
350 : 12980 : bool uniqueouter;
351 : 12980 : bool uniqueinner;
352 : :
353 : 12980 : elidedouter = pgpa_last_elided_node(pstmt, outerplan);
354 : 12980 : elidedinner = pgpa_last_elided_node(pstmt, innerplan);
355 : 12980 : *found_any_outer_gather = false;
356 : 12980 : *found_any_inner_gather = false;
357 : :
358 [ + + + - ]: 12980 : switch (nodeTag(plan))
359 : : {
360 : : case T_MergeJoin:
361 : :
362 : : /*
363 : : * The planner may have chosen to place a Material node on the
364 : : * inner side of the MergeJoin; if this is present, we record it
365 : : * as part of the join strategy.
366 : : */
367 [ + - + + ]: 508 : if (elidedinner == NULL && IsA(innerplan, Material))
368 : : {
369 : 26 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
370 : 26 : strategy = JSTRAT_MERGE_JOIN_MATERIALIZE;
371 : 26 : }
372 : : else
373 : 482 : strategy = JSTRAT_MERGE_JOIN_PLAIN;
374 : :
375 : : /*
376 : : * For a MergeJoin, either the outer or the inner subplan, or
377 : : * both, may have needed to be sorted; we must disregard any Sort
378 : : * or IncrementalSort node to find the real inner or outer
379 : : * subplan.
380 : : */
381 [ + + + + ]: 508 : if (elidedouter == NULL && is_sorting_plan(outerplan))
382 : 335 : elidedouter = pgpa_descend_node(pstmt, &outerplan);
383 [ + + + + ]: 508 : if (elidedinner == NULL && is_sorting_plan(innerplan))
384 : 442 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
385 : 508 : break;
386 : :
387 : : case T_NestLoop:
388 : :
389 : : /*
390 : : * The planner may have chosen to place a Material or Memoize node
391 : : * on the inner side of the NestLoop; if this is present, we
392 : : * record it as part of the join strategy.
393 : : */
394 [ + + + + ]: 9141 : if (elidedinner == NULL && IsA(innerplan, Material))
395 : : {
396 : 496 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
397 : 496 : strategy = JSTRAT_NESTED_LOOP_MATERIALIZE;
398 : 496 : }
399 [ + + + + ]: 8645 : else if (elidedinner == NULL && IsA(innerplan, Memoize))
400 : : {
401 : 215 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
402 : 215 : strategy = JSTRAT_NESTED_LOOP_MEMOIZE;
403 : 215 : }
404 : : else
405 : 8430 : strategy = JSTRAT_NESTED_LOOP_PLAIN;
406 : 9141 : break;
407 : :
408 : : case T_HashJoin:
409 : :
410 : : /*
411 : : * The inner subplan of a HashJoin is always a Hash node; the real
412 : : * inner subplan is the Hash node's child.
413 : : */
414 [ + - ]: 3331 : Assert(IsA(innerplan, Hash));
415 [ + - ]: 3331 : Assert(elidedinner == NULL);
416 : 3331 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
417 : 3331 : strategy = JSTRAT_HASH_JOIN;
418 : 3331 : break;
419 : :
420 : : default:
421 [ # # # # ]: 0 : elog(ERROR, "unrecognized node type: %d", (int) nodeTag(plan));
422 : 0 : }
423 : :
424 : : /*
425 : : * The planner may have decided to implement a semijoin by first making
426 : : * the nullable side of the plan unique, and then performing a normal join
427 : : * against the result. Therefore, we might need to descend through a
428 : : * unique node on either side of the plan.
429 : : */
430 : 12980 : uniqueouter = pgpa_descend_any_unique(pstmt, &outerplan, &elidedouter);
431 : 12980 : uniqueinner = pgpa_descend_any_unique(pstmt, &innerplan, &elidedinner);
432 : :
433 : : /*
434 : : * The planner may have decided to parallelize part of the join tree, so
435 : : * we could find a Gather or Gather Merge node here. Note that, if
436 : : * present, this will appear below nodes we considered as part of the join
437 : : * strategy, but we could find another uniqueness-enforcing node below the
438 : : * Gather or Gather Merge, if present.
439 : : */
440 [ + + ]: 12980 : if (elidedouter == NULL)
441 : : {
442 : 25800 : elidedouter = pgpa_descend_any_gather(pstmt, &outerplan,
443 : 12900 : found_any_outer_gather);
444 [ + - + + ]: 12900 : if (found_any_outer_gather &&
445 : 12900 : pgpa_descend_any_unique(pstmt, &outerplan, &elidedouter))
446 : 1 : uniqueouter = true;
447 : 12900 : }
448 [ + + ]: 12980 : if (elidedinner == NULL)
449 : : {
450 : 25650 : elidedinner = pgpa_descend_any_gather(pstmt, &innerplan,
451 : 12825 : found_any_inner_gather);
452 [ + - + - ]: 12825 : if (found_any_inner_gather &&
453 : 12825 : pgpa_descend_any_unique(pstmt, &innerplan, &elidedinner))
454 : 0 : uniqueinner = true;
455 : 12825 : }
456 : :
457 : : /*
458 : : * It's possible that Result node has been inserted either to project a
459 : : * target list or to implement a one-time filter. If so, we can descend
460 : : * throught it. Note that a result node without a child would be a
461 : : * degenerate scan or join, and not something we could descend through.
462 : : *
463 : : * XXX. I suspect it's possible for this to happen above the Gather or
464 : : * Gather Merge node, too, but apparently we have no test case for that
465 : : * scenario.
466 : : */
467 [ + + + + ]: 12980 : if (elidedouter == NULL && is_result_node_with_child(outerplan))
468 : 3 : elidedouter = pgpa_descend_node(pstmt, &outerplan);
469 [ + + + + ]: 12980 : if (elidedinner == NULL && is_result_node_with_child(innerplan))
470 : 3 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
471 : :
472 : : /*
473 : : * If this is a semijoin that was converted to an inner join by making one
474 : : * side or the other unique, make a note that the inner or outer subplan,
475 : : * as appropriate, should be treated as a query plan feature when the main
476 : : * tree traversal reaches it.
477 : : *
478 : : * Conversely, if the planner could have made one side of the join unique
479 : : * and thereby converted it to an inner join, and chose not to do so, that
480 : : * is also worth noting.
481 : : *
482 : : * NB: This code could appear slightly higher up in in this function, but
483 : : * none of the nodes through which we just descended should have
484 : : * associated RTIs.
485 : : *
486 : : * NB: This seems like a somewhat hacky way of passing information up to
487 : : * the main tree walk, but I don't currently have a better idea.
488 : : */
489 [ + + ]: 12980 : if (uniqueouter)
490 : 40 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_UNIQUE, outerplan);
491 [ + + ]: 12940 : else if (jointype == JOIN_RIGHT_SEMI)
492 : 39 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_NON_UNIQUE, outerplan);
493 [ + + ]: 12980 : if (uniqueinner)
494 : 41 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_UNIQUE, innerplan);
495 [ + + ]: 12939 : else if (jointype == JOIN_SEMI)
496 : 605 : pgpa_add_future_feature(walker, PGPAQF_SEMIJOIN_NON_UNIQUE, innerplan);
497 : :
498 : : /* Set output parameters. */
499 : 12980 : *realouter = outerplan;
500 : 12980 : *realinner = innerplan;
501 : 12980 : *elidedrealouter = elidedouter;
502 : 12980 : *elidedrealinner = elidedinner;
503 : 25960 : return strategy;
504 : 12980 : }
505 : :
506 : : /*
507 : : * Descend through a Plan node in a join tree that the caller has determined
508 : : * to be irrelevant.
509 : : *
510 : : * Updates *plan, and returns the last of any elided nodes pertaining to the
511 : : * new plan node.
512 : : */
513 : : static ElidedNode *
514 : 5120 : pgpa_descend_node(PlannedStmt *pstmt, Plan **plan)
515 : : {
516 : 5120 : *plan = (*plan)->lefttree;
517 : 5120 : return pgpa_last_elided_node(pstmt, *plan);
518 : : }
519 : :
520 : : /*
521 : : * Descend through a Gather or Gather Merge node, if present, and any Sort
522 : : * or IncrementalSort node occurring under a Gather Merge.
523 : : *
524 : : * Caller should have verified that there is no ElidedNode pertaining to
525 : : * the initial value of *plan.
526 : : *
527 : : * Updates *plan, and returns the last of any elided nodes pertaining to the
528 : : * new plan node. Sets *found_any_gather = true if either Gather or
529 : : * Gather Merge was found, and otherwise leaves it unchanged.
530 : : */
531 : : static ElidedNode *
532 : 25725 : pgpa_descend_any_gather(PlannedStmt *pstmt, Plan **plan,
533 : : bool *found_any_gather)
534 : : {
535 [ + + ]: 25725 : if (IsA(*plan, Gather))
536 : : {
537 : 28 : *found_any_gather = true;
538 : 28 : return pgpa_descend_node(pstmt, plan);
539 : : }
540 : :
541 [ + + ]: 25697 : if (IsA(*plan, GatherMerge))
542 : : {
543 : 11 : ElidedNode *elided = pgpa_descend_node(pstmt, plan);
544 : :
545 [ + - - + ]: 11 : if (elided == NULL && is_sorting_plan(*plan))
546 : 11 : elided = pgpa_descend_node(pstmt, plan);
547 : :
548 : 11 : *found_any_gather = true;
549 : 11 : return elided;
550 : 11 : }
551 : :
552 : 25686 : return NULL;
553 : 25725 : }
554 : :
555 : : /*
556 : : * If *plan is an Agg or Unique node, we want to descend through it, unless
557 : : * it has a corresponding elided node. If its immediate child is a Sort or
558 : : * IncrementalSort, we also want to descend through that, unless it has a
559 : : * corresponding elided node.
560 : : *
561 : : * On entry, *elided_node must be the last of any elided nodes corresponding
562 : : * to *plan; on exit, this will still be true, but *plan may have been updated.
563 : : *
564 : : * The reason we don't want to descend through elided nodes is that a single
565 : : * join tree can't cross through any sort of elided node: subqueries are
566 : : * planned separately, and planning inside an Append or MergeAppend is
567 : : * separate from planning outside of it.
568 : : *
569 : : * The return value is true if we descend through a node that we believe is
570 : : * making one side of a semijoin unique, and otherwise false.
571 : : */
572 : : static bool
573 : 51685 : pgpa_descend_any_unique(PlannedStmt *pstmt, Plan **plan,
574 : : ElidedNode **elided_node)
575 : : {
576 : 51685 : bool descend = false;
577 : 51685 : bool sjunique = false;
578 : :
579 [ + + ]: 51685 : if (*elided_node != NULL)
580 : 229 : return sjunique;
581 : :
582 [ + + ]: 51456 : if (IsA(*plan, Unique))
583 : : {
584 : 30 : descend = true;
585 : 30 : sjunique = true;
586 : 30 : }
587 [ + + ]: 51426 : else if (IsA(*plan, Agg))
588 : : {
589 : : /*
590 : : * If this is a simple Agg node, then assume it's here to implement
591 : : * semijoin uniqueness. Otherwise, assume it's completing an eager
592 : : * aggregation or partitionwise aggregation operation that began at a
593 : : * higher level of the plan tree.
594 : : *
595 : : * XXX. I suspect this logic does not cover all cases: couldn't SJ
596 : : * uniqueness be implemented in two steps with an intermediate Gather?
597 : : */
598 : 159 : descend = true;
599 : 159 : sjunique = (((Agg *) *plan)->aggsplit == AGGSPLIT_SIMPLE);
600 : 159 : }
601 : :
602 [ + + ]: 51456 : if (descend)
603 : : {
604 : 189 : *elided_node = pgpa_descend_node(pstmt, plan);
605 : :
606 [ + + + + ]: 189 : if (*elided_node == NULL && is_sorting_plan(*plan))
607 : 30 : *elided_node = pgpa_descend_node(pstmt, plan);
608 : 189 : }
609 : :
610 : 51456 : return sjunique;
611 : 51685 : }
612 : :
613 : : /*
614 : : * Is this a Result node that has a child?
615 : : */
616 : : static bool
617 : 38706 : is_result_node_with_child(Plan *plan)
618 : : {
619 [ + + ]: 38706 : return IsA(plan, Result) && plan->lefttree != NULL;
620 : : }
621 : :
622 : : /*
623 : : * Is this a Plan node whose purpose is put the data in a certain order?
624 : : */
625 : : static bool
626 : 14293 : is_sorting_plan(Plan *plan)
627 : : {
628 [ + + ]: 14293 : return IsA(plan, Sort) || IsA(plan, IncrementalSort);
629 : : }
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