Age Owner Branch data TLA 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 *
3 rhaas@postgresql.org 64 :GNC 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 [ - + ]: 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 : : {
3 rhaas@postgresql.org 168 :UNC 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 : : */
3 rhaas@postgresql.org 198 [ + - + + ]:GNC 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 [ - + ]: 87 : 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 [ - + ]: 53 : Assert(IsA(innerplan, Hash));
416 [ - + ]: 53 : Assert(elidedinner == NULL);
417 : 53 : elidedinner = pgpa_descend_node(pstmt, &innerplan);
418 : 53 : strategy = JSTRAT_HASH_JOIN;
419 : 53 : break;
420 : :
3 rhaas@postgresql.org 421 :UNC 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 : : */
3 rhaas@postgresql.org 431 :GNC 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))
3 rhaas@postgresql.org 454 :UNC 0 : uniqueouter = true;
455 : : }
3 rhaas@postgresql.org 456 [ + - ]:GNC 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))
3 rhaas@postgresql.org 462 :UNC 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 : : */
3 rhaas@postgresql.org 471 [ + - - + ]:GNC 116 : if (elidedouter == NULL && is_result_node_with_child(outerplan))
3 rhaas@postgresql.org 472 :UNC 0 : elidedouter = pgpa_descend_node(pstmt, &outerplan);
3 rhaas@postgresql.org 473 [ + - - + ]:GNC 116 : if (elidedinner == NULL && is_result_node_with_child(innerplan))
3 rhaas@postgresql.org 474 :UNC 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 : : */
3 rhaas@postgresql.org 493 [ + + ]:GNC 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)
3 rhaas@postgresql.org 584 :UNC 0 : return sjunique;
585 : :
3 rhaas@postgresql.org 586 [ - + ]:GNC 241 : if (IsA(*plan, Unique))
587 : : {
3 rhaas@postgresql.org 588 :UNC 0 : descend = true;
589 : 0 : sjunique = true;
590 : : }
3 rhaas@postgresql.org 591 [ + + ]:GNC 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))
3 rhaas@postgresql.org 616 :UNC 0 : *elided_node = pgpa_descend_node(pstmt, plan);
617 : : }
618 : :
3 rhaas@postgresql.org 619 :GNC 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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