Line data Source code
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 234816 : 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 234816 : pgpa_scan_strategy strategy = PGPA_SCAN_ORDINARY;
49 234816 : Bitmapset *relids = NULL;
50 234816 : int rti = -1;
51 234816 : List *child_append_relid_sets = NIL;
52 234816 : NodeTag nodetype = nodeTag(plan);
53 :
54 234816 : if (elided_node != NULL)
55 : {
56 5630 : nodetype = elided_node->elided_type;
57 5630 : 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 5630 : if ((nodetype == T_Append || nodetype == T_MergeAppend) &&
79 1208 : relids != NULL &&
80 1208 : unique_nonjoin_rtekind(relids,
81 1208 : walker->pstmt->rtable) == RTE_RELATION)
82 1196 : strategy = PGPA_SCAN_PARTITIONWISE;
83 : else
84 4434 : strategy = PGPA_SCAN_ORDINARY;
85 :
86 : /* Join RTIs can be present, but advice never refers to them. */
87 5630 : relids = pgpa_filter_out_join_relids(relids, walker->pstmt->rtable);
88 : }
89 229186 : else if ((rti = pgpa_scanrelid(plan)) != 0)
90 : {
91 101797 : relids = bms_make_singleton(rti);
92 :
93 101797 : switch (nodeTag(plan))
94 : {
95 53954 : case T_SeqScan:
96 53954 : strategy = PGPA_SCAN_SEQ;
97 53954 : break;
98 5325 : case T_BitmapHeapScan:
99 5325 : strategy = PGPA_SCAN_BITMAP_HEAP;
100 5325 : break;
101 23629 : case T_IndexScan:
102 23629 : strategy = PGPA_SCAN_INDEX;
103 23629 : break;
104 3843 : case T_IndexOnlyScan:
105 3843 : strategy = PGPA_SCAN_INDEX_ONLY;
106 3843 : break;
107 840 : case T_TidScan:
108 : case T_TidRangeScan:
109 840 : strategy = PGPA_SCAN_TID;
110 840 : break;
111 14206 : 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 14206 : strategy = PGPA_SCAN_ORDINARY;
120 14206 : break;
121 : }
122 : }
123 127389 : 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 127387 : else if ((relids = pgpa_relids(plan)) != NULL)
135 : {
136 42842 : switch (nodeTag(plan))
137 : {
138 0 : 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.
145 : */
146 0 : strategy = PGPA_SCAN_FOREIGN;
147 0 : break;
148 5085 : case T_Append:
149 :
150 : /*
151 : * Append nodes can represent partitionwise scans of a
152 : * relation, but when they implement a set operation, they are
153 : * just ordinary scans.
154 : */
155 5085 : if (unique_nonjoin_rtekind(relids, walker->pstmt->rtable)
156 : == RTE_RELATION)
157 2441 : strategy = PGPA_SCAN_PARTITIONWISE;
158 : else
159 2644 : strategy = PGPA_SCAN_ORDINARY;
160 :
161 : /* Be sure to account for pulled-up scans. */
162 5085 : child_append_relid_sets =
163 : ((Append *) plan)->child_append_relid_sets;
164 5085 : break;
165 162 : case T_MergeAppend:
166 : /* Same logic here as for Append, above. */
167 162 : if (unique_nonjoin_rtekind(relids, walker->pstmt->rtable)
168 : == RTE_RELATION)
169 96 : strategy = PGPA_SCAN_PARTITIONWISE;
170 : else
171 66 : strategy = PGPA_SCAN_ORDINARY;
172 :
173 : /* Be sure to account for pulled-up scans. */
174 162 : child_append_relid_sets =
175 : ((MergeAppend *) plan)->child_append_relid_sets;
176 162 : break;
177 37595 : default:
178 37595 : strategy = PGPA_SCAN_ORDINARY;
179 37595 : break;
180 : }
181 :
182 :
183 : /* Join RTIs can be present, but advice never refers to them. */
184 42842 : relids = pgpa_filter_out_join_relids(relids, walker->pstmt->rtable);
185 : }
186 :
187 : /*
188 : * If this is an Append or MergeAppend node into which subordinate Append
189 : * or MergeAppend paths were merged, each of those merged paths is
190 : * effectively another scan for which we need to account.
191 : */
192 470372 : foreach_node(Bitmapset, child_relids, child_append_relid_sets)
193 : {
194 : Bitmapset *child_nonjoin_relids;
195 :
196 : child_nonjoin_relids =
197 740 : pgpa_filter_out_join_relids(child_relids,
198 740 : walker->pstmt->rtable);
199 740 : (void) pgpa_make_scan(walker, plan, strategy,
200 : child_nonjoin_relids);
201 : }
202 :
203 : /*
204 : * If this plan node has no associated RTIs, it's not a scan. When the
205 : * 'within_join_problem' flag is set, that's unexpected, so throw an
206 : * error, else return quietly.
207 : */
208 234816 : if (relids == NULL)
209 : {
210 84545 : if (within_join_problem)
211 0 : elog(ERROR, "plan node has no RTIs: %d", (int) nodeTag(plan));
212 84545 : return NULL;
213 : }
214 :
215 : /*
216 : * Add the appropriate set of RTIs to walker->no_gather_scans.
217 : *
218 : * Add nothing if we're beneath a Gather or Gather Merge node, since
219 : * NO_GATHER advice is clearly inappropriate in that situation.
220 : *
221 : * Add nothing if this is an Append or MergeAppend node, whether or not
222 : * elided. We'll emit NO_GATHER() for the underlying scan, which is good
223 : * enough.
224 : */
225 150271 : if (!beneath_any_gather && nodetype != T_Append &&
226 : nodetype != T_MergeAppend)
227 142397 : walker->no_gather_scans =
228 142397 : bms_add_members(walker->no_gather_scans, relids);
229 :
230 : /* Caller tells us whether NO_GATHER() advice for this scan is needed. */
231 150271 : return pgpa_make_scan(walker, plan, strategy, relids);
232 : }
233 :
234 : /*
235 : * Create a single pgpa_scan object and update the pgpa_plan_walker_context.
236 : */
237 : static pgpa_scan *
238 151011 : pgpa_make_scan(pgpa_plan_walker_context *walker, Plan *plan,
239 : pgpa_scan_strategy strategy, Bitmapset *relids)
240 : {
241 : pgpa_scan *scan;
242 :
243 : /* Create the scan object. */
244 151011 : scan = palloc(sizeof(pgpa_scan));
245 151011 : scan->plan = plan;
246 151011 : scan->strategy = strategy;
247 151011 : scan->relids = relids;
248 :
249 : /* Add it to the appropriate list. */
250 151011 : walker->scans[scan->strategy] = lappend(walker->scans[scan->strategy],
251 : scan);
252 :
253 151011 : return scan;
254 : }
255 :
256 : /*
257 : * Determine the unique rtekind of a set of relids.
258 : */
259 : static RTEKind
260 6455 : unique_nonjoin_rtekind(Bitmapset *relids, List *rtable)
261 : {
262 6455 : int rti = -1;
263 6455 : bool first = true;
264 6455 : RTEKind rtekind = RTE_RELATION; /* silence compiler warning */
265 :
266 : Assert(relids != NULL);
267 :
268 15919 : while ((rti = bms_next_member(relids, rti)) >= 0)
269 : {
270 9464 : RangeTblEntry *rte = rt_fetch(rti, rtable);
271 :
272 9464 : if (rte->rtekind == RTE_JOIN)
273 182 : continue;
274 :
275 9282 : if (first)
276 : {
277 6455 : rtekind = rte->rtekind;
278 6455 : first = false;
279 : }
280 2827 : else if (rtekind != rte->rtekind)
281 0 : elog(ERROR, "rtekind mismatch: %d vs. %d",
282 : rtekind, rte->rtekind);
283 : }
284 :
285 6455 : if (first)
286 0 : elog(ERROR, "no non-RTE_JOIN RTEs found");
287 :
288 6455 : return rtekind;
289 : }
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