make_join_rel.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * make_join_rel.c
   4  *        Routines copied from PostgreSQL core distribution with some
   5  *        modifications.
   6  *
   7  * src/backend/optimizer/path/joinrels.c
   8  *     make_join_rel()
   9  *
  10  * Portions Copyright (c) 2013-2017, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
  11  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
  12  * Portions Copyright (c) 1994, Regents of the University of California
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16
  17 static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
  18                                                                                 RelOptInfo *rel2, RelOptInfo *joinrel,
  19                                                                                 SpecialJoinInfo *sjinfo,
  20                                                                                 List *restrictlist);
  21 /*
  22  * adjust_rows: tweak estimated row numbers according to the hint.
  23  */
  24 static double
  25 adjust_rows(double rows, RowsHint *hint)
  26 {
  27         double          result = 0.0;   /* keep compiler quiet */
  28
  29         if (hint->value_type == RVT_ABSOLUTE)
  30                 result = hint->rows;
  31         else if (hint->value_type == RVT_ADD)
  32                 result = rows + hint->rows;
  33         else if (hint->value_type == RVT_SUB)
  34                 result =  rows - hint->rows;
  35         else if (hint->value_type == RVT_MULTI)
  36                 result = rows * hint->rows;
  37         else
  38                 Assert(false);  /* unrecognized rows value type */
  39
  40         hint->base.state = HINT_STATE_USED;
  41         if (result < 1.0)
  42                 ereport(WARNING,
  43                                 (errmsg("Force estimate to be at least one row, to avoid possible divide-by-zero when interpolating costs : %s",
  44                                         hint->base.hint_str)));
  45         result = clamp_row_est(result);
  46         elog(DEBUG1, "adjusted rows %d to %d", (int) rows, (int) result);
  47
  48         return result;
  49 }
  50
  51 /*
  52  * make_join_rel
  53  *         Find or create a join RelOptInfo that represents the join of
  54  *         the two given rels, and add to it path information for paths
  55  *         created with the two rels as outer and inner rel.
  56  *         (The join rel may already contain paths generated from other
  57  *         pairs of rels that add up to the same set of base rels.)
  58  *
  59  * NB: will return NULL if attempted join is not valid.  This can happen
  60  * when working with outer joins, or with IN or EXISTS clauses that have been
  61  * turned into joins.
  62  */
  63 RelOptInfo *
  64 make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
  65 {
  66         Relids          joinrelids;
  67         SpecialJoinInfo *sjinfo;
  68         bool            reversed;
  69         SpecialJoinInfo sjinfo_data;
  70         RelOptInfo *joinrel;
  71         List       *restrictlist;
  72
  73         /* We should never try to join two overlapping sets of rels. */
  74         Assert(!bms_overlap(rel1->relids, rel2->relids));
  75
  76         /* Construct Relids set that identifies the joinrel. */
  77         joinrelids = bms_union(rel1->relids, rel2->relids);
  78
  79         /* Check validity and determine join type. */
  80         if (!join_is_legal(root, rel1, rel2, joinrelids,
  81                                            &sjinfo, &reversed))
  82         {
  83                 /* invalid join path */
  84                 bms_free(joinrelids);
  85                 return NULL;
  86         }
  87
  88         /* Swap rels if needed to match the join info. */
  89         if (reversed)
  90         {
  91                 RelOptInfo *trel = rel1;
  92
  93                 rel1 = rel2;
  94                 rel2 = trel;
  95         }
  96
  97         /*
  98          * If it's a plain inner join, then we won't have found anything in
  99          * join_info_list.  Make up a SpecialJoinInfo so that selectivity
 100          * estimation functions will know what's being joined.
 101          */
 102         if (sjinfo == NULL)
 103         {
 104                 sjinfo = &sjinfo_data;
 105                 sjinfo->type = T_SpecialJoinInfo;
 106                 sjinfo->min_lefthand = rel1->relids;
 107                 sjinfo->min_righthand = rel2->relids;
 108                 sjinfo->syn_lefthand = rel1->relids;
 109                 sjinfo->syn_righthand = rel2->relids;
 110                 sjinfo->jointype = JOIN_INNER;
 111                 /* we don't bother trying to make the remaining fields valid */
 112                 sjinfo->lhs_strict = false;
 113                 sjinfo->delay_upper_joins = false;
 114                 sjinfo->semi_can_btree = false;
 115                 sjinfo->semi_can_hash = false;
 116                 sjinfo->semi_operators = NIL;
 117                 sjinfo->semi_rhs_exprs = NIL;
 118         }
 119
 120         /*
 121          * Find or build the join RelOptInfo, and compute the restrictlist that
 122          * goes with this particular joining.
 123          */
 124         joinrel = build_join_rel(root, joinrelids, rel1, rel2, sjinfo,
 125                                                          &restrictlist);
 126
 127         /* !!! START: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
 128         {
 129                 RowsHint   *rows_hint = NULL;
 130                 int                     i;
 131                 RowsHint   *justforme = NULL;
 132                 RowsHint   *domultiply = NULL;
 133
 134                 /* Search for applicable rows hint for this join node */
 135                 for (i = 0; i < current_hint_state->num_hints[HINT_TYPE_ROWS]; i++)
 136                 {
 137                         rows_hint = current_hint_state->rows_hints[i];
 138
 139                         /*
 140                          * Skip this rows_hint if it is invalid from the first or it
 141                          * doesn't target any join rels.
 142                          */
 143                         if (!rows_hint->joinrelids ||
 144                                 rows_hint->base.state == HINT_STATE_ERROR)
 145                                 continue;
 146
 147                         if (bms_equal(joinrelids, rows_hint->joinrelids))
 148                         {
 149                                 /*
 150                                  * This joinrel is just the target of this rows_hint, so tweak
 151                                  * rows estimation according to the hint.
 152                                  */
 153                                 justforme = rows_hint;
 154                         }
 155                         else if (!(bms_is_subset(rows_hint->joinrelids, rel1->relids) ||
 156                                            bms_is_subset(rows_hint->joinrelids, rel2->relids)) &&
 157                                          bms_is_subset(rows_hint->joinrelids, joinrelids) &&
 158                                          rows_hint->value_type == RVT_MULTI)
 159                         {
 160                                 /*
 161                                  * If the rows_hint's target relids is not a subset of both of
 162                                  * component rels and is a subset of this joinrel, ths hint's
 163                                  * targets spread over both component rels. This menas that
 164                                  * this hint has been never applied so far and this joinrel is
 165                                  * the first (and only) chance to fire in current join tree.
 166                                  * Only the multiplication hint has the cumulative nature so we
 167                                  * apply only RVT_MULTI in this way.
 168                                  */
 169                                 domultiply = rows_hint;
 170                         }
 171                 }
 172
 173                 if (justforme)
 174                 {
 175                         /*
 176                          * If a hint just for me is found, no other adjust method is
 177                          * useles, but this cannot be more than twice becuase this joinrel
 178                          * is already adjusted by this hint.
 179                          */
 180                         if (justforme->base.state == HINT_STATE_NOTUSED)
 181                                 joinrel->rows = adjust_rows(joinrel->rows, justforme);
 182                 }
 183                 else
 184                 {
 185                         if (domultiply)
 186                         {
 187                                 /*
 188                                  * If we have multiple routes up to this joinrel which are not
 189                                  * applicable this hint, this multiply hint will applied more
 190                                  * than twice. But there's no means to know of that,
 191                                  * re-estimate the row number of this joinrel always just
 192                                  * before applying the hint. This is a bit different from
 193                                  * normal planner behavior but it doesn't harm so much.
 194                                  */
 195                                 set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
 196                                                                                    restrictlist);
 197
 198                                 joinrel->rows = adjust_rows(joinrel->rows, domultiply);
 199                         }
 200
 201                 }
 202         }
 203         /* !!! END: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
 204
 205         /*
 206          * If we've already proven this join is empty, we needn't consider any
 207          * more paths for it.
 208          */
 209         if (is_dummy_rel(joinrel))
 210         {
 211                 bms_free(joinrelids);
 212                 return joinrel;
 213         }
 214
 215         /* Add paths to the join relation. */
 216         populate_joinrel_with_paths(root, rel1, rel2, joinrel, sjinfo,
 217                                                                 restrictlist);
 218
 219         bms_free(joinrelids);
 220
 221         return joinrel;
 222 }
 223
 224 /*
 225  * populate_joinrel_with_paths
 226  *        Add paths to the given joinrel for given pair of joining relations. The
 227  *        SpecialJoinInfo provides details about the join and the restrictlist
 228  *        contains the join clauses and the other clauses applicable for given pair
 229  *        of the joining relations.
 230  */
 231 static void
 232 populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
 233                                                         RelOptInfo *rel2, RelOptInfo *joinrel,
 234                                                         SpecialJoinInfo *sjinfo, List *restrictlist)
 235 {
 236         /*
 237          * Consider paths using each rel as both outer and inner.  Depending on
 238          * the join type, a provably empty outer or inner rel might mean the join
 239          * is provably empty too; in which case throw away any previously computed
 240          * paths and mark the join as dummy.  (We do it this way since it's
 241          * conceivable that dummy-ness of a multi-element join might only be
 242          * noticeable for certain construction paths.)
 243          *
 244          * Also, a provably constant-false join restriction typically means that
 245          * we can skip evaluating one or both sides of the join.  We do this by
 246          * marking the appropriate rel as dummy.  For outer joins, a
 247          * constant-false restriction that is pushed down still means the whole
 248          * join is dummy, while a non-pushed-down one means that no inner rows
 249          * will join so we can treat the inner rel as dummy.
 250          *
 251          * We need only consider the jointypes that appear in join_info_list, plus
 252          * JOIN_INNER.
 253          */
 254         switch (sjinfo->jointype)
 255         {
 256                 case JOIN_INNER:
 257                         if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 258                                 restriction_is_constant_false(restrictlist, false))
 259                         {
 260                                 mark_dummy_rel(joinrel);
 261                                 break;
 262                         }
 263                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 264                                                                  JOIN_INNER, sjinfo,
 265                                                                  restrictlist);
 266                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 267                                                                  JOIN_INNER, sjinfo,
 268                                                                  restrictlist);
 269                         break;
 270                 case JOIN_LEFT:
 271                         if (is_dummy_rel(rel1) ||
 272                                 restriction_is_constant_false(restrictlist, true))
 273                         {
 274                                 mark_dummy_rel(joinrel);
 275                                 break;
 276                         }
 277                         if (restriction_is_constant_false(restrictlist, false) &&
 278                                 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
 279                                 mark_dummy_rel(rel2);
 280                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 281                                                                  JOIN_LEFT, sjinfo,
 282                                                                  restrictlist);
 283                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 284                                                                  JOIN_RIGHT, sjinfo,
 285                                                                  restrictlist);
 286                         break;
 287                 case JOIN_FULL:
 288                         if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
 289                                 restriction_is_constant_false(restrictlist, true))
 290                         {
 291                                 mark_dummy_rel(joinrel);
 292                                 break;
 293                         }
 294                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 295                                                                  JOIN_FULL, sjinfo,
 296                                                                  restrictlist);
 297                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 298                                                                  JOIN_FULL, sjinfo,
 299                                                                  restrictlist);
 300
 301                         /*
 302                          * If there are join quals that aren't mergeable or hashable, we
 303                          * may not be able to build any valid plan.  Complain here so that
 304                          * we can give a somewhat-useful error message.  (Since we have no
 305                          * flexibility of planning for a full join, there's no chance of
 306                          * succeeding later with another pair of input rels.)
 307                          */
 308                         if (joinrel->pathlist == NIL)
 309                                 ereport(ERROR,
 310                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 311                                                  errmsg("FULL JOIN is only supported with merge-joinable or hash-joinable join conditions")));
 312                         break;
 313                 case JOIN_SEMI:
 314
 315                         /*
 316                          * We might have a normal semijoin, or a case where we don't have
 317                          * enough rels to do the semijoin but can unique-ify the RHS and
 318                          * then do an innerjoin (see comments in join_is_legal).  In the
 319                          * latter case we can't apply JOIN_SEMI joining.
 320                          */
 321                         if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
 322                                 bms_is_subset(sjinfo->min_righthand, rel2->relids))
 323                         {
 324                                 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 325                                         restriction_is_constant_false(restrictlist, false))
 326                                 {
 327                                         mark_dummy_rel(joinrel);
 328                                         break;
 329                                 }
 330                                 add_paths_to_joinrel(root, joinrel, rel1, rel2,
 331                                                                          JOIN_SEMI, sjinfo,
 332                                                                          restrictlist);
 333                         }
 334
 335                         /*
 336                          * If we know how to unique-ify the RHS and one input rel is
 337                          * exactly the RHS (not a superset) we can consider unique-ifying
 338                          * it and then doing a regular join.  (The create_unique_path
 339                          * check here is probably redundant with what join_is_legal did,
 340                          * but if so the check is cheap because it's cached.  So test
 341                          * anyway to be sure.)
 342                          */
 343                         if (bms_equal(sjinfo->syn_righthand, rel2->relids) &&
 344                                 create_unique_path(root, rel2, rel2->cheapest_total_path,
 345                                                                    sjinfo) != NULL)
 346                         {
 347                                 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 348                                         restriction_is_constant_false(restrictlist, false))
 349                                 {
 350                                         mark_dummy_rel(joinrel);
 351                                         break;
 352                                 }
 353                                 add_paths_to_joinrel(root, joinrel, rel1, rel2,
 354                                                                          JOIN_UNIQUE_INNER, sjinfo,
 355                                                                          restrictlist);
 356                                 add_paths_to_joinrel(root, joinrel, rel2, rel1,
 357                                                                          JOIN_UNIQUE_OUTER, sjinfo,
 358                                                                          restrictlist);
 359                         }
 360                         break;
 361                 case JOIN_ANTI:
 362                         if (is_dummy_rel(rel1) ||
 363                                 restriction_is_constant_false(restrictlist, true))
 364                         {
 365                                 mark_dummy_rel(joinrel);
 366                                 break;
 367                         }
 368                         if (restriction_is_constant_false(restrictlist, false) &&
 369                                 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
 370                                 mark_dummy_rel(rel2);
 371                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 372                                                                  JOIN_ANTI, sjinfo,
 373                                                                  restrictlist);
 374                         break;
 375                 default:
 376                         /* other values not expected here */
 377                         elog(ERROR, "unrecognized join type: %d", (int) sjinfo->jointype);
 378                         break;
 379         }
 380 }