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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * planmain.c
4 : : * Routines to plan a single query
5 : : *
6 : : * What's in a name, anyway? The top-level entry point of the planner/
7 : : * optimizer is over in planner.c, not here as you might think from the
8 : : * file name. But this is the main code for planning a basic join operation,
9 : : * shorn of features like subselects, inheritance, aggregates, grouping,
10 : : * and so on. (Those are the things planner.c deals with.)
11 : : *
12 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
13 : : * Portions Copyright (c) 1994, Regents of the University of California
14 : : *
15 : : *
16 : : * IDENTIFICATION
17 : : * src/backend/optimizer/plan/planmain.c
18 : : *
19 : : *-------------------------------------------------------------------------
20 : : */
21 : : #include "postgres.h"
22 : :
23 : : #include "optimizer/appendinfo.h"
24 : : #include "optimizer/clauses.h"
25 : : #include "optimizer/optimizer.h"
26 : : #include "optimizer/orclauses.h"
27 : : #include "optimizer/pathnode.h"
28 : : #include "optimizer/paths.h"
29 : : #include "optimizer/placeholder.h"
30 : : #include "optimizer/planmain.h"
31 : :
32 : :
33 : : /*
34 : : * query_planner
35 : : * Generate a path (that is, a simplified plan) for a basic query,
36 : : * which may involve joins but not any fancier features.
37 : : *
38 : : * Since query_planner does not handle the toplevel processing (grouping,
39 : : * sorting, etc) it cannot select the best path by itself. Instead, it
40 : : * returns the RelOptInfo for the top level of joining, and the caller
41 : : * (grouping_planner) can choose among the surviving paths for the rel.
42 : : *
43 : : * root describes the query to plan
44 : : * qp_callback is a function to compute query_pathkeys once it's safe to do so
45 : : * qp_extra is optional extra data to pass to qp_callback
46 : : *
47 : : * Note: the PlannerInfo node also includes a query_pathkeys field, which
48 : : * tells query_planner the sort order that is desired in the final output
49 : : * plan. This value is *not* available at call time, but is computed by
50 : : * qp_callback once we have completed merging the query's equivalence classes.
51 : : * (We cannot construct canonical pathkeys until that's done.)
52 : : */
53 : : RelOptInfo *
54 : 51007 : query_planner(PlannerInfo *root,
55 : : query_pathkeys_callback qp_callback, void *qp_extra)
56 : : {
57 : 51007 : Query *parse = root->parse;
58 : 51007 : List *joinlist;
59 : 51007 : RelOptInfo *final_rel;
60 : :
61 : : /*
62 : : * Init planner lists to empty.
63 : : *
64 : : * NOTE: append_rel_list was set up by subquery_planner, so do not touch
65 : : * here.
66 : : */
67 : 51007 : root->join_rel_list = NIL;
68 : 51007 : root->join_rel_hash = NULL;
69 : 51007 : root->join_rel_level = NULL;
70 : 51007 : root->join_cur_level = 0;
71 : 51007 : root->canon_pathkeys = NIL;
72 : 51007 : root->left_join_clauses = NIL;
73 : 51007 : root->right_join_clauses = NIL;
74 : 51007 : root->full_join_clauses = NIL;
75 : 51007 : root->join_info_list = NIL;
76 : 51007 : root->placeholder_list = NIL;
77 : 51007 : root->placeholder_array = NULL;
78 : 51007 : root->placeholder_array_size = 0;
79 : 51007 : root->agg_clause_list = NIL;
80 : 51007 : root->group_expr_list = NIL;
81 : 51007 : root->tlist_vars = NIL;
82 : 51007 : root->fkey_list = NIL;
83 : 51007 : root->initial_rels = NIL;
84 : :
85 : : /*
86 : : * Set up arrays for accessing base relations and AppendRelInfos.
87 : : */
88 : 51007 : setup_simple_rel_arrays(root);
89 : :
90 : : /*
91 : : * In the trivial case where the jointree is a single RTE_RESULT relation,
92 : : * bypass all the rest of this function and just make a RelOptInfo and its
93 : : * one access path. This is worth optimizing because it applies for
94 : : * common cases like "SELECT expression" and "INSERT ... VALUES()".
95 : : */
96 [ + - ]: 51007 : Assert(parse->jointree->fromlist != NIL);
97 [ + + ]: 51007 : if (list_length(parse->jointree->fromlist) == 1)
98 : : {
99 : 47369 : Node *jtnode = (Node *) linitial(parse->jointree->fromlist);
100 : :
101 [ + + ]: 47369 : if (IsA(jtnode, RangeTblRef))
102 : : {
103 : 40864 : int varno = ((RangeTblRef *) jtnode)->rtindex;
104 : 40864 : RangeTblEntry *rte = root->simple_rte_array[varno];
105 : :
106 [ + - ]: 40864 : Assert(rte != NULL);
107 [ + + ]: 40864 : if (rte->rtekind == RTE_RESULT)
108 : : {
109 : : /* Make the RelOptInfo for it directly */
110 : 17111 : final_rel = build_simple_rel(root, varno, NULL);
111 : :
112 : : /*
113 : : * If query allows parallelism in general, check whether the
114 : : * quals are parallel-restricted. (We need not check
115 : : * final_rel->reltarget because it's empty at this point.
116 : : * Anything parallel-restricted in the query tlist will be
117 : : * dealt with later.) We should always do this in a subquery,
118 : : * since it might be useful to use the subquery in parallel
119 : : * paths in the parent level. At top level this is normally
120 : : * not worth the cycles, because a Result-only plan would
121 : : * never be interesting to parallelize. However, if
122 : : * debug_parallel_query is on, then we want to execute the
123 : : * Result in a parallel worker if possible, so we must check.
124 : : */
125 [ + + + + ]: 27310 : if (root->glob->parallelModeOK &&
126 [ + + ]: 11060 : (root->query_level > 1 ||
127 : 10199 : debug_parallel_query != DEBUG_PARALLEL_OFF))
128 : 877 : final_rel->consider_parallel =
129 : 877 : is_parallel_safe(root, parse->jointree->quals);
130 : :
131 : : /*
132 : : * The only path for it is a trivial Result path. We cheat a
133 : : * bit here by using a GroupResultPath, because that way we
134 : : * can just jam the quals into it without preprocessing them.
135 : : * (But, if you hold your head at the right angle, a FROM-less
136 : : * SELECT is a kind of degenerate-grouping case, so it's not
137 : : * that much of a cheat.)
138 : : */
139 : 34222 : add_path(final_rel, (Path *)
140 : 34222 : create_group_result_path(root, final_rel,
141 : 17111 : final_rel->reltarget,
142 : 17111 : (List *) parse->jointree->quals));
143 : :
144 : : /* Select cheapest path (pretty easy in this case...) */
145 : 17111 : set_cheapest(final_rel);
146 : :
147 : : /*
148 : : * We don't need to run generate_base_implied_equalities, but
149 : : * we do need to pretend that EC merging is complete.
150 : : */
151 : 17111 : root->ec_merging_done = true;
152 : :
153 : : /*
154 : : * We still are required to call qp_callback, in case it's
155 : : * something like "SELECT 2+2 ORDER BY 1".
156 : : */
157 : 17111 : (*qp_callback) (root, qp_extra);
158 : :
159 : 17111 : return final_rel;
160 : : }
161 [ + + ]: 40864 : }
162 [ + + ]: 47369 : }
163 : :
164 : : /*
165 : : * Construct RelOptInfo nodes for all base relations used in the query.
166 : : * Appendrel member relations ("other rels") will be added later.
167 : : *
168 : : * Note: the reason we find the baserels by searching the jointree, rather
169 : : * than scanning the rangetable, is that the rangetable may contain RTEs
170 : : * for rels not actively part of the query, for example views. We don't
171 : : * want to make RelOptInfos for them.
172 : : */
173 : 33896 : add_base_rels_to_query(root, (Node *) parse->jointree);
174 : :
175 : : /* Remove any redundant GROUP BY columns */
176 : 33896 : remove_useless_groupby_columns(root);
177 : :
178 : : /*
179 : : * Examine the targetlist and join tree, adding entries to baserel
180 : : * targetlists for all referenced Vars, and generating PlaceHolderInfo
181 : : * entries for all referenced PlaceHolderVars. Restrict and join clauses
182 : : * are added to appropriate lists belonging to the mentioned relations. We
183 : : * also build EquivalenceClasses for provably equivalent expressions. The
184 : : * SpecialJoinInfo list is also built to hold information about join order
185 : : * restrictions. Finally, we form a target joinlist for make_one_rel() to
186 : : * work from.
187 : : */
188 : 33896 : build_base_rel_tlists(root, root->processed_tlist);
189 : :
190 : 33896 : find_placeholders_in_jointree(root);
191 : :
192 : 33896 : find_lateral_references(root);
193 : :
194 : 33896 : joinlist = deconstruct_jointree(root);
195 : :
196 : : /*
197 : : * Reconsider any postponed outer-join quals now that we have built up
198 : : * equivalence classes. (This could result in further additions or
199 : : * mergings of classes.)
200 : : */
201 : 33896 : reconsider_outer_join_clauses(root);
202 : :
203 : : /*
204 : : * If we formed any equivalence classes, generate additional restriction
205 : : * clauses as appropriate. (Implied join clauses are formed on-the-fly
206 : : * later.)
207 : : */
208 : 33896 : generate_base_implied_equalities(root);
209 : :
210 : : /*
211 : : * We have completed merging equivalence sets, so it's now possible to
212 : : * generate pathkeys in canonical form; so compute query_pathkeys and
213 : : * other pathkeys fields in PlannerInfo.
214 : : */
215 : 33896 : (*qp_callback) (root, qp_extra);
216 : :
217 : : /*
218 : : * Examine any "placeholder" expressions generated during subquery pullup.
219 : : * Make sure that the Vars they need are marked as needed at the relevant
220 : : * join level. This must be done before join removal because it might
221 : : * cause Vars or placeholders to be needed above a join when they weren't
222 : : * so marked before.
223 : : */
224 : 33896 : fix_placeholder_input_needed_levels(root);
225 : :
226 : : /*
227 : : * Remove any useless outer joins. Ideally this would be done during
228 : : * jointree preprocessing, but the necessary information isn't available
229 : : * until we've built baserel data structures and classified qual clauses.
230 : : */
231 : 33896 : joinlist = remove_useless_joins(root, joinlist);
232 : :
233 : : /*
234 : : * Also, reduce any semijoins with unique inner rels to plain inner joins.
235 : : * Likewise, this can't be done until now for lack of needed info.
236 : : */
237 : 33896 : reduce_unique_semijoins(root);
238 : :
239 : : /*
240 : : * Remove self joins on a unique column.
241 : : */
242 : 33896 : joinlist = remove_useless_self_joins(root, joinlist);
243 : :
244 : : /*
245 : : * Now distribute "placeholders" to base rels as needed. This has to be
246 : : * done after join removal because removal could change whether a
247 : : * placeholder is evaluable at a base rel.
248 : : */
249 : 33896 : add_placeholders_to_base_rels(root);
250 : :
251 : : /*
252 : : * Construct the lateral reference sets now that we have finalized
253 : : * PlaceHolderVar eval levels.
254 : : */
255 : 33896 : create_lateral_join_info(root);
256 : :
257 : : /*
258 : : * Match foreign keys to equivalence classes and join quals. This must be
259 : : * done after finalizing equivalence classes, and it's useful to wait till
260 : : * after join removal so that we can skip processing foreign keys
261 : : * involving removed relations.
262 : : */
263 : 33896 : match_foreign_keys_to_quals(root);
264 : :
265 : : /*
266 : : * Look for join OR clauses that we can extract single-relation
267 : : * restriction OR clauses from.
268 : : */
269 : 33896 : extract_restriction_or_clauses(root);
270 : :
271 : : /*
272 : : * Check if eager aggregation is applicable, and if so, set up
273 : : * root->agg_clause_list and root->group_expr_list.
274 : : */
275 : 33896 : setup_eager_aggregation(root);
276 : :
277 : : /*
278 : : * Now expand appendrels by adding "otherrels" for their children. We
279 : : * delay this to the end so that we have as much information as possible
280 : : * available for each baserel, including all restriction clauses. That
281 : : * let us prune away partitions that don't satisfy a restriction clause.
282 : : * Also note that some information such as lateral_relids is propagated
283 : : * from baserels to otherrels here, so we must have computed it already.
284 : : */
285 : 33896 : add_other_rels_to_query(root);
286 : :
287 : : /*
288 : : * Distribute any UPDATE/DELETE/MERGE row identity variables to the target
289 : : * relations. This can't be done till we've finished expansion of
290 : : * appendrels.
291 : : */
292 : 33896 : distribute_row_identity_vars(root);
293 : :
294 : : /*
295 : : * Ready to do the primary planning.
296 : : */
297 : 33896 : final_rel = make_one_rel(root, joinlist);
298 : :
299 : : /* Check that we got at least one usable path */
300 [ + - ]: 33896 : if (!final_rel || !final_rel->cheapest_total_path ||
301 : 33896 : final_rel->cheapest_total_path->param_info != NULL)
302 [ # # # # ]: 0 : elog(ERROR, "failed to construct the join relation");
303 : :
304 : 33896 : return final_rel;
305 : 51007 : }
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