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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * pgpa_scan.c
4 : : * analysis of scans in Plan trees
5 : : *
6 : : * Copyright (c) 2016-2026, PostgreSQL Global Development Group
7 : : *
8 : : * contrib/pg_plan_advice/pgpa_scan.c
9 : : *
10 : : *-------------------------------------------------------------------------
11 : : */
12 : : #include "postgres.h"
13 : :
14 : : #include "pgpa_scan.h"
15 : : #include "pgpa_walker.h"
16 : :
17 : : #include "nodes/parsenodes.h"
18 : : #include "parser/parsetree.h"
19 : :
20 : : static pgpa_scan *pgpa_make_scan(pgpa_plan_walker_context *walker, Plan *plan,
21 : : pgpa_scan_strategy strategy,
22 : : Bitmapset *relids);
23 : :
24 : :
25 : : static RTEKind unique_nonjoin_rtekind(Bitmapset *relids, List *rtable);
26 : :
27 : : /*
28 : : * Build a pgpa_scan object for a Plan node and update the plan walker
29 : : * context as appropriate. If this is an Append or MergeAppend scan, also
30 : : * build pgpa_scan for any scans that were consolidated into this one by
31 : : * Append/MergeAppend pull-up.
32 : : *
33 : : * If there is at least one ElidedNode for this plan node, pass the uppermost
34 : : * one as elided_node, else pass NULL.
35 : : *
36 : : * Set the 'beneath_any_gather' node if we are underneath a Gather or
37 : : * Gather Merge node (except for a single-copy Gather node, for which
38 : : * GATHER or GATHER_MERGE advice should not be emitted).
39 : : *
40 : : * Set the 'within_join_problem' flag if we're inside of a join problem and
41 : : * not otherwise.
42 : : */
43 : : pgpa_scan *
44 : 235871 : pgpa_build_scan(pgpa_plan_walker_context *walker, Plan *plan,
45 : : ElidedNode *elided_node,
46 : : bool beneath_any_gather, bool within_join_problem)
47 : : {
48 : 235871 : pgpa_scan_strategy strategy = PGPA_SCAN_ORDINARY;
49 : 235871 : Bitmapset *relids = NULL;
50 : 235871 : int rti = -1;
51 : 235871 : List *child_append_relid_sets = NIL;
52 : 235871 : NodeTag nodetype = nodeTag(plan);
53 : :
54 [ + + ]: 235871 : if (elided_node != NULL)
55 : : {
56 : 5780 : nodetype = elided_node->elided_type;
57 : 5780 : relids = elided_node->relids;
58 : :
59 : : /*
60 : : * If setrefs processing elided an Append or MergeAppend node that had
61 : : * only one surviving child, it could be either a partitionwise
62 : : * operation or a setop over subqueries, depending on the rtekind.
63 : : *
64 : : * A setop over subqueries, or a trivial SubqueryScan that was elided,
65 : : * is an "ordinary" scan i.e. one for which we do not need to generate
66 : : * advice because the planner has not made any meaningful choice.
67 : : *
68 : : * Note that the PGPA_SCAN_PARTITIONWISE case also includes
69 : : * partitionwise joins; this module considers those to be a form of
70 : : * scan, since they lack internal structure that we can decompose.
71 : : *
72 : : * Note also that it's possible for relids to be NULL here, if the
73 : : * elided Append node is part of a partitionwise aggregate. In that
74 : : * case, it doesn't matter what strategy we choose, but we do need to
75 : : * avoid calling unique_nonjoin_rtekind(), which would fail an
76 : : * assertion.
77 : : */
78 [ + + - + : 5780 : if ((nodetype == T_Append || nodetype == T_MergeAppend) &&
+ - ]
79 [ + + ]: 1210 : relids != NULL &&
80 : 1210 : unique_nonjoin_rtekind(relids,
81 : 1210 : walker->pstmt->rtable) == RTE_RELATION)
82 : 1198 : strategy = PGPA_SCAN_PARTITIONWISE;
83 : : else
84 : 4582 : strategy = PGPA_SCAN_ORDINARY;
85 : :
86 : : /* Join RTIs can be present, but advice never refers to them. */
87 : 5780 : relids = pgpa_filter_out_join_relids(relids, walker->pstmt->rtable);
88 : : }
89 [ + + ]: 230091 : else if ((rti = pgpa_scanrelid(plan)) != 0)
90 : : {
91 : 102060 : relids = bms_make_singleton(rti);
92 : :
93 [ + + + + : 102060 : switch (nodeTag(plan))
+ + ]
94 : : {
95 : 52532 : case T_SeqScan:
96 : 52532 : strategy = PGPA_SCAN_SEQ;
97 : 52532 : break;
98 : 5381 : case T_BitmapHeapScan:
99 : 5381 : strategy = PGPA_SCAN_BITMAP_HEAP;
100 : 5381 : break;
101 : 25351 : case T_IndexScan:
102 : 25351 : strategy = PGPA_SCAN_INDEX;
103 : 25351 : break;
104 : 3561 : case T_IndexOnlyScan:
105 : 3561 : strategy = PGPA_SCAN_INDEX_ONLY;
106 : 3561 : break;
107 : 840 : case T_TidScan:
108 : : case T_TidRangeScan:
109 : 840 : strategy = PGPA_SCAN_TID;
110 : 840 : break;
111 : 14395 : default:
112 : :
113 : : /*
114 : : * This case includes a ForeignScan targeting a single
115 : : * relation; no other strategy is possible in that case, but
116 : : * see below, where things are different in multi-relation
117 : : * cases.
118 : : */
119 : 14395 : strategy = PGPA_SCAN_ORDINARY;
120 : 14395 : break;
121 : : }
122 : : }
123 [ + + ]: 128031 : else if (pgpa_is_scan_level_materialize(plan))
124 : : {
125 : : /*
126 : : * Non-repeatable tablesample methods can be wrapped in a Materialize
127 : : * node that must be treated as part of the scan itself. See
128 : : * set_tablesample_rel_pathlist().
129 : : */
130 : 2 : rti = pgpa_scanrelid(plan->lefttree);
131 : 2 : relids = bms_make_singleton(rti);
132 : 2 : strategy = PGPA_SCAN_ORDINARY;
133 : : }
134 [ + + ]: 128029 : else if ((relids = pgpa_relids(plan)) != NULL)
135 : : {
136 [ + + + + ]: 43387 : switch (nodeTag(plan))
137 : : {
138 : 2 : case T_ForeignScan:
139 : :
140 : : /*
141 : : * If multiple relations are being targeted by a single
142 : : * foreign scan, then the foreign join has been pushed to the
143 : : * remote side, and we want that to be reflected in the
144 : : * generated advice. We can't emit FOREIGN_JOIN() advice for a
145 : : * single relation, so treat that case as an ordinary scan.
146 : : */
147 [ + + ]: 2 : if (bms_membership(relids) == BMS_MULTIPLE)
148 : 1 : strategy = PGPA_SCAN_FOREIGN;
149 : : else
150 : 1 : strategy = PGPA_SCAN_ORDINARY;
151 : 2 : break;
152 : 5149 : case T_Append:
153 : :
154 : : /*
155 : : * Append nodes can represent partitionwise scans of a
156 : : * relation, but when they implement a set operation, they are
157 : : * just ordinary scans.
158 : : */
159 [ + + ]: 5149 : if (unique_nonjoin_rtekind(relids, walker->pstmt->rtable)
160 : : == RTE_RELATION)
161 : 2471 : strategy = PGPA_SCAN_PARTITIONWISE;
162 : : else
163 : 2678 : strategy = PGPA_SCAN_ORDINARY;
164 : :
165 : : /* Be sure to account for pulled-up scans. */
166 : 5149 : child_append_relid_sets =
167 : : ((Append *) plan)->child_append_relid_sets;
168 : 5149 : break;
169 : 154 : case T_MergeAppend:
170 : : /* Same logic here as for Append, above. */
171 [ + + ]: 154 : if (unique_nonjoin_rtekind(relids, walker->pstmt->rtable)
172 : : == RTE_RELATION)
173 : 96 : strategy = PGPA_SCAN_PARTITIONWISE;
174 : : else
175 : 58 : strategy = PGPA_SCAN_ORDINARY;
176 : :
177 : : /* Be sure to account for pulled-up scans. */
178 : 154 : child_append_relid_sets =
179 : : ((MergeAppend *) plan)->child_append_relid_sets;
180 : 154 : break;
181 : 38082 : default:
182 : 38082 : strategy = PGPA_SCAN_ORDINARY;
183 : 38082 : break;
184 : : }
185 : :
186 : :
187 : : /* Join RTIs can be present, but advice never refers to them. */
188 : 43387 : relids = pgpa_filter_out_join_relids(relids, walker->pstmt->rtable);
189 : : }
190 : :
191 : : /*
192 : : * If this is an Append or MergeAppend node into which subordinate Append
193 : : * or MergeAppend paths were merged, each of those merged paths is
194 : : * effectively another scan for which we need to account.
195 : : */
196 [ + + + + : 472474 : foreach_node(Bitmapset, child_relids, child_append_relid_sets)
+ + ]
197 : : {
198 : : Bitmapset *child_nonjoin_relids;
199 : :
200 : : child_nonjoin_relids =
201 : 732 : pgpa_filter_out_join_relids(child_relids,
202 : 732 : walker->pstmt->rtable);
203 : 732 : (void) pgpa_make_scan(walker, plan, strategy,
204 : : child_nonjoin_relids);
205 : : }
206 : :
207 : : /*
208 : : * If this plan node has no associated RTIs, it's not a scan. When the
209 : : * 'within_join_problem' flag is set, that's unexpected, so throw an
210 : : * error, else return quietly.
211 : : */
212 [ + + ]: 235871 : if (relids == NULL)
213 : : {
214 [ - + ]: 84642 : if (within_join_problem)
215 [ # # ]: 0 : elog(ERROR, "plan node has no RTIs: %d", (int) nodeTag(plan));
216 : 84642 : return NULL;
217 : : }
218 : :
219 : : /*
220 : : * Add the appropriate set of RTIs to walker->no_gather_scans.
221 : : *
222 : : * Add nothing if we're beneath a Gather or Gather Merge node, since
223 : : * NO_GATHER advice is clearly inappropriate in that situation.
224 : : *
225 : : * Add nothing if this is an Append or MergeAppend node, whether or not
226 : : * elided. We'll emit NO_GATHER() for the underlying scan, which is good
227 : : * enough.
228 : : */
229 [ + + + + : 151229 : if (!beneath_any_gather && nodetype != T_Append &&
+ + ]
230 : : nodetype != T_MergeAppend)
231 : 143315 : walker->no_gather_scans =
232 : 143315 : bms_add_members(walker->no_gather_scans, relids);
233 : :
234 : : /* Caller tells us whether NO_GATHER() advice for this scan is needed. */
235 : 151229 : return pgpa_make_scan(walker, plan, strategy, relids);
236 : : }
237 : :
238 : : /*
239 : : * Create a single pgpa_scan object and update the pgpa_plan_walker_context.
240 : : */
241 : : static pgpa_scan *
242 : 151961 : pgpa_make_scan(pgpa_plan_walker_context *walker, Plan *plan,
243 : : pgpa_scan_strategy strategy, Bitmapset *relids)
244 : : {
245 : : pgpa_scan *scan;
246 : :
247 : : /* Create the scan object. */
248 : 151961 : scan = palloc(sizeof(pgpa_scan));
249 : 151961 : scan->plan = plan;
250 : 151961 : scan->strategy = strategy;
251 : 151961 : scan->relids = relids;
252 : :
253 : : /* Add it to the appropriate list. */
254 : 151961 : walker->scans[scan->strategy] = lappend(walker->scans[scan->strategy],
255 : : scan);
256 : :
257 : 151961 : return scan;
258 : : }
259 : :
260 : : /*
261 : : * Determine the unique rtekind of a set of relids.
262 : : */
263 : : static RTEKind
264 : 6513 : unique_nonjoin_rtekind(Bitmapset *relids, List *rtable)
265 : : {
266 : 6513 : int rti = -1;
267 : 6513 : bool first = true;
268 : 6513 : RTEKind rtekind = RTE_RELATION; /* silence compiler warning */
269 : :
270 : : Assert(relids != NULL);
271 : :
272 [ + + ]: 16057 : while ((rti = bms_next_member(relids, rti)) >= 0)
273 : : {
274 : 9544 : RangeTblEntry *rte = rt_fetch(rti, rtable);
275 : :
276 [ + + ]: 9544 : if (rte->rtekind == RTE_JOIN)
277 : 182 : continue;
278 : :
279 [ + + ]: 9362 : if (first)
280 : : {
281 : 6513 : rtekind = rte->rtekind;
282 : 6513 : first = false;
283 : : }
284 [ - + ]: 2849 : else if (rtekind != rte->rtekind)
285 [ # # ]: 0 : elog(ERROR, "rtekind mismatch: %d vs. %d",
286 : : rtekind, rte->rtekind);
287 : : }
288 : :
289 [ - + ]: 6513 : if (first)
290 [ # # ]: 0 : elog(ERROR, "no non-RTE_JOIN RTEs found");
291 : :
292 : 6513 : return rtekind;
293 : : }
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