1 /*-------------------------------------------------------------------------
4 * Routines copied from PostgreSQL core distribution.
6 * src/backend/optimizer/path/joinrels.c
9 * Portions Copyright (c) 2013, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
10 * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
11 * Portions Copyright (c) 1994, Regents of the University of California
13 *-------------------------------------------------------------------------
18 * Find or create a join RelOptInfo that represents the join of
19 * the two given rels, and add to it path information for paths
20 * created with the two rels as outer and inner rel.
21 * (The join rel may already contain paths generated from other
22 * pairs of rels that add up to the same set of base rels.)
24 * NB: will return NULL if attempted join is not valid. This can happen
25 * when working with outer joins, or with IN or EXISTS clauses that have been
29 adjust_rows(double rows, RowsHint *hint)
31 double result = 0.0; /* keep compiler quiet */
33 if (hint->value_type == RVT_ABSOLUTE)
35 else if (hint->value_type == RVT_ADD)
36 result = rows + hint->rows;
37 else if (hint->value_type == RVT_SUB)
38 result = rows - hint->rows;
39 else if (hint->value_type == RVT_MULTI)
40 result = rows * hint->rows;
42 Assert(false); /* unrecognized rows value type */
44 hint->base.state = HINT_STATE_USED;
47 (errmsg("make rows estimation 1 since below 1 : %s",
48 hint->base.hint_str)));
49 result = clamp_row_est(result);
50 elog(DEBUG1, "adjusted rows %d to %d", (int) rows, (int) result);
56 make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
59 SpecialJoinInfo *sjinfo;
61 SpecialJoinInfo sjinfo_data;
65 RowsHint *rows_hint = NULL;
68 /* We should never try to join two overlapping sets of rels. */
69 Assert(!bms_overlap(rel1->relids, rel2->relids));
71 /* Construct Relids set that identifies the joinrel. */
72 joinrelids = bms_union(rel1->relids, rel2->relids);
74 /* Check validity and determine join type. */
75 if (!join_is_legal(root, rel1, rel2, joinrelids,
78 /* invalid join path */
83 /* Swap rels if needed to match the join info. */
86 RelOptInfo *trel = rel1;
93 * If it's a plain inner join, then we won't have found anything in
94 * join_info_list. Make up a SpecialJoinInfo so that selectivity
95 * estimation functions will know what's being joined.
99 sjinfo = &sjinfo_data;
100 sjinfo->type = T_SpecialJoinInfo;
101 sjinfo->min_lefthand = rel1->relids;
102 sjinfo->min_righthand = rel2->relids;
103 sjinfo->syn_lefthand = rel1->relids;
104 sjinfo->syn_righthand = rel2->relids;
105 sjinfo->jointype = JOIN_INNER;
106 /* we don't bother trying to make the remaining fields valid */
107 sjinfo->lhs_strict = false;
108 sjinfo->delay_upper_joins = false;
109 sjinfo->join_quals = NIL;
113 * Find or build the join RelOptInfo, and compute the restrictlist that
114 * goes with this particular joining.
116 joinrel = build_join_rel(root, joinrelids, rel1, rel2, sjinfo,
119 /* Apply appropriate Rows hint to the join node, if any. */
120 for (i = 0; i < current_hint->num_hints[HINT_TYPE_ROWS]; i++)
122 rows_hint = current_hint->rows_hints[i];
125 * This Rows hint specifies aliasname is error, or does not exist in
128 if (!rows_hint->joinrelids ||
129 rows_hint->base.state == HINT_STATE_ERROR)
131 if (bms_equal(joinrelids, rows_hint->joinrelids))
134 * This join RelOptInfo is exactly a Rows hint specifies, so adjust
135 * rows estimateion with the hint's content. Here we never have
136 * another hint which has same relation combination, so we can skip
139 if (rows_hint->base.state == HINT_STATE_NOTUSED)
140 joinrel->rows = adjust_rows(joinrel->rows, rows_hint);
142 else if (bms_is_subset(rows_hint->joinrelids, rel1->relids) ||
143 bms_is_subset(rows_hint->joinrelids, rel2->relids))
146 * Otherwise if the relation combination specified in thee Rows
147 * hint is subset of the set of join elements, re-estimate rows and
148 * costs again to reflect the adjustment done in down. This is
149 * necessary for the first permutation of the combination the
150 * relations, but it's difficult to determine that this is the
151 * first, so do this everytime.
153 set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
156 else if (bms_is_subset(rows_hint->joinrelids, joinrelids))
159 * If the combination specifed in the Rows hints is subset of the
160 * join relation and spreads over both children,
162 * We do adjust rows estimation only when the value type was
163 * multiplication, because other value types are meanless.
165 if (rows_hint->value_type == RVT_MULTI)
167 set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
169 joinrel->rows = adjust_rows(joinrel->rows, rows_hint);
175 * If we've already proven this join is empty, we needn't consider any
178 if (is_dummy_rel(joinrel))
180 bms_free(joinrelids);
185 * Consider paths using each rel as both outer and inner. Depending on
186 * the join type, a provably empty outer or inner rel might mean the join
187 * is provably empty too; in which case throw away any previously computed
188 * paths and mark the join as dummy. (We do it this way since it's
189 * conceivable that dummy-ness of a multi-element join might only be
190 * noticeable for certain construction paths.)
192 * Also, a provably constant-false join restriction typically means that
193 * we can skip evaluating one or both sides of the join. We do this by
194 * marking the appropriate rel as dummy. For outer joins, a
195 * constant-false restriction that is pushed down still means the whole
196 * join is dummy, while a non-pushed-down one means that no inner rows
197 * will join so we can treat the inner rel as dummy.
199 * We need only consider the jointypes that appear in join_info_list, plus
202 switch (sjinfo->jointype)
205 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
206 restriction_is_constant_false(restrictlist, false))
208 mark_dummy_rel(joinrel);
211 add_paths_to_joinrel(root, joinrel, rel1, rel2,
214 add_paths_to_joinrel(root, joinrel, rel2, rel1,
219 if (is_dummy_rel(rel1) ||
220 restriction_is_constant_false(restrictlist, true))
222 mark_dummy_rel(joinrel);
225 if (restriction_is_constant_false(restrictlist, false) &&
226 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
227 mark_dummy_rel(rel2);
228 add_paths_to_joinrel(root, joinrel, rel1, rel2,
231 add_paths_to_joinrel(root, joinrel, rel2, rel1,
236 if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
237 restriction_is_constant_false(restrictlist, true))
239 mark_dummy_rel(joinrel);
242 add_paths_to_joinrel(root, joinrel, rel1, rel2,
245 add_paths_to_joinrel(root, joinrel, rel2, rel1,
250 * If there are join quals that aren't mergeable or hashable, we
251 * may not be able to build any valid plan. Complain here so that
252 * we can give a somewhat-useful error message. (Since we have no
253 * flexibility of planning for a full join, there's no chance of
254 * succeeding later with another pair of input rels.)
256 if (joinrel->pathlist == NIL)
258 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
259 errmsg("FULL JOIN is only supported with merge-joinable or hash-joinable join conditions")));
264 * We might have a normal semijoin, or a case where we don't have
265 * enough rels to do the semijoin but can unique-ify the RHS and
266 * then do an innerjoin (see comments in join_is_legal). In the
267 * latter case we can't apply JOIN_SEMI joining.
269 if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
270 bms_is_subset(sjinfo->min_righthand, rel2->relids))
272 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
273 restriction_is_constant_false(restrictlist, false))
275 mark_dummy_rel(joinrel);
278 add_paths_to_joinrel(root, joinrel, rel1, rel2,
284 * If we know how to unique-ify the RHS and one input rel is
285 * exactly the RHS (not a superset) we can consider unique-ifying
286 * it and then doing a regular join. (The create_unique_path
287 * check here is probably redundant with what join_is_legal did,
288 * but if so the check is cheap because it's cached. So test
289 * anyway to be sure.)
291 if (bms_equal(sjinfo->syn_righthand, rel2->relids) &&
292 create_unique_path(root, rel2, rel2->cheapest_total_path,
295 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
296 restriction_is_constant_false(restrictlist, false))
298 mark_dummy_rel(joinrel);
301 add_paths_to_joinrel(root, joinrel, rel1, rel2,
302 JOIN_UNIQUE_INNER, sjinfo,
304 add_paths_to_joinrel(root, joinrel, rel2, rel1,
305 JOIN_UNIQUE_OUTER, sjinfo,
310 if (is_dummy_rel(rel1) ||
311 restriction_is_constant_false(restrictlist, true))
313 mark_dummy_rel(joinrel);
316 if (restriction_is_constant_false(restrictlist, false) &&
317 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
318 mark_dummy_rel(rel2);
319 add_paths_to_joinrel(root, joinrel, rel1, rel2,
324 /* other values not expected here */
325 elog(ERROR, "unrecognized join type: %d", (int) sjinfo->jointype);
329 bms_free(joinrelids);