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) 2013-2020, NIPPON TELEGRAPH AND TELEPHONE CORPORATION
  11  * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
  12  * Portions Copyright (c) 1994, Regents of the University of California
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16
  17 /*
  18  * adjust_rows: tweak estimated row numbers according to the hint.
  19  */
  20 static double
  21 adjust_rows(double rows, RowsHint *hint)
  22 {
  23         double          result = 0.0;   /* keep compiler quiet */
  24
  25         if (hint->value_type == RVT_ABSOLUTE)
  26                 result = hint->rows;
  27         else if (hint->value_type == RVT_ADD)
  28                 result = rows + hint->rows;
  29         else if (hint->value_type == RVT_SUB)
  30                 result =  rows - hint->rows;
  31         else if (hint->value_type == RVT_MULTI)
  32                 result = rows * hint->rows;
  33         else
  34                 Assert(false);  /* unrecognized rows value type */
  35
  36         hint->base.state = HINT_STATE_USED;
  37         if (result < 1.0)
  38                 ereport(WARNING,
  39                                 (errmsg("Force estimate to be at least one row, to avoid possible divide-by-zero when interpolating costs : %s",
  40                                         hint->base.hint_str)));
  41         result = clamp_row_est(result);
  42         elog(DEBUG1, "adjusted rows %d to %d", (int) rows, (int) result);
  43
  44         return result;
  45 }
  46
  47 /*
  48  * make_join_rel
  49  *         Find or create a join RelOptInfo that represents the join of
  50  *         the two given rels, and add to it path information for paths
  51  *         created with the two rels as outer and inner rel.
  52  *         (The join rel may already contain paths generated from other
  53  *         pairs of rels that add up to the same set of base rels.)
  54  *
  55  * NB: will return NULL if attempted join is not valid.  This can happen
  56  * when working with outer joins, or with IN or EXISTS clauses that have been
  57  * turned into joins.
  58  */
  59 RelOptInfo *
  60 make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
  61 {
  62         Relids          joinrelids;
  63         SpecialJoinInfo *sjinfo;
  64         bool            reversed;
  65         SpecialJoinInfo sjinfo_data;
  66         RelOptInfo *joinrel;
  67         List       *restrictlist;
  68
  69         /* We should never try to join two overlapping sets of rels. */
  70         Assert(!bms_overlap(rel1->relids, rel2->relids));
  71
  72         /* Construct Relids set that identifies the joinrel. */
  73         joinrelids = bms_union(rel1->relids, rel2->relids);
  74
  75         /* Check validity and determine join type. */
  76         if (!join_is_legal(root, rel1, rel2, joinrelids,
  77                                            &sjinfo, &reversed))
  78         {
  79                 /* invalid join path */
  80                 bms_free(joinrelids);
  81                 return NULL;
  82         }
  83
  84         /* Swap rels if needed to match the join info. */
  85         if (reversed)
  86         {
  87                 RelOptInfo *trel = rel1;
  88
  89                 rel1 = rel2;
  90                 rel2 = trel;
  91         }
  92
  93         /*
  94          * If it's a plain inner join, then we won't have found anything in
  95          * join_info_list.  Make up a SpecialJoinInfo so that selectivity
  96          * estimation functions will know what's being joined.
  97          */
  98         if (sjinfo == NULL)
  99         {
 100                 sjinfo = &sjinfo_data;
 101                 sjinfo->type = T_SpecialJoinInfo;
 102                 sjinfo->min_lefthand = rel1->relids;
 103                 sjinfo->min_righthand = rel2->relids;
 104                 sjinfo->syn_lefthand = rel1->relids;
 105                 sjinfo->syn_righthand = rel2->relids;
 106                 sjinfo->jointype = JOIN_INNER;
 107                 /* we don't bother trying to make the remaining fields valid */
 108                 sjinfo->lhs_strict = false;
 109                 sjinfo->delay_upper_joins = false;
 110                 sjinfo->semi_can_btree = false;
 111                 sjinfo->semi_can_hash = false;
 112                 sjinfo->semi_operators = NIL;
 113                 sjinfo->semi_rhs_exprs = NIL;
 114         }
 115
 116         /*
 117          * Find or build the join RelOptInfo, and compute the restrictlist that
 118          * goes with this particular joining.
 119          */
 120         joinrel = build_join_rel(root, joinrelids, rel1, rel2, sjinfo,
 121                                                          &restrictlist);
 122
 123         /* !!! START: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
 124         {
 125                 RowsHint   *rows_hint = NULL;
 126                 int                     i;
 127                 RowsHint   *justforme = NULL;
 128                 RowsHint   *domultiply = NULL;
 129
 130                 /* Search for applicable rows hint for this join node */
 131                 for (i = 0; i < current_hint_state->num_hints[HINT_TYPE_ROWS]; i++)
 132                 {
 133                         rows_hint = current_hint_state->rows_hints[i];
 134
 135                         /*
 136                          * Skip this rows_hint if it is invalid from the first or it
 137                          * doesn't target any join rels.
 138                          */
 139                         if (!rows_hint->joinrelids ||
 140                                 rows_hint->base.state == HINT_STATE_ERROR)
 141                                 continue;
 142
 143                         if (bms_equal(joinrelids, rows_hint->joinrelids))
 144                         {
 145                                 /*
 146                                  * This joinrel is just the target of this rows_hint, so tweak
 147                                  * rows estimation according to the hint.
 148                                  */
 149                                 justforme = rows_hint;
 150                         }
 151                         else if (!(bms_is_subset(rows_hint->joinrelids, rel1->relids) ||
 152                                            bms_is_subset(rows_hint->joinrelids, rel2->relids)) &&
 153                                          bms_is_subset(rows_hint->joinrelids, joinrelids) &&
 154                                          rows_hint->value_type == RVT_MULTI)
 155                         {
 156                                 /*
 157                                  * If the rows_hint's target relids is not a subset of both of
 158                                  * component rels and is a subset of this joinrel, ths hint's
 159                                  * targets spread over both component rels. This menas that
 160                                  * this hint has been never applied so far and this joinrel is
 161                                  * the first (and only) chance to fire in current join tree.
 162                                  * Only the multiplication hint has the cumulative nature so we
 163                                  * apply only RVT_MULTI in this way.
 164                                  */
 165                                 domultiply = rows_hint;
 166                         }
 167                 }
 168
 169                 if (justforme)
 170                 {
 171                         /*
 172                          * If a hint just for me is found, no other adjust method is
 173                          * useles, but this cannot be more than twice becuase this joinrel
 174                          * is already adjusted by this hint.
 175                          */
 176                         if (justforme->base.state == HINT_STATE_NOTUSED)
 177                                 joinrel->rows = adjust_rows(joinrel->rows, justforme);
 178                 }
 179                 else
 180                 {
 181                         if (domultiply)
 182                         {
 183                                 /*
 184                                  * If we have multiple routes up to this joinrel which are not
 185                                  * applicable this hint, this multiply hint will applied more
 186                                  * than twice. But there's no means to know of that,
 187                                  * re-estimate the row number of this joinrel always just
 188                                  * before applying the hint. This is a bit different from
 189                                  * normal planner behavior but it doesn't harm so much.
 190                                  */
 191                                 set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
 192                                                                                    restrictlist);
 193
 194                                 joinrel->rows = adjust_rows(joinrel->rows, domultiply);
 195                         }
 196
 197                 }
 198         }
 199         /* !!! END: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
 200
 201         /*
 202          * If we've already proven this join is empty, we needn't consider any
 203          * more paths for it.
 204          */
 205         if (is_dummy_rel(joinrel))
 206         {
 207                 bms_free(joinrelids);
 208                 return joinrel;
 209         }
 210
 211         /* Add paths to the join relation. */
 212         populate_joinrel_with_paths(root, rel1, rel2, joinrel, sjinfo,
 213                                                                 restrictlist);
 214
 215         bms_free(joinrelids);
 216
 217         return joinrel;
 218 }
 219
 220 /*
 221  * populate_joinrel_with_paths
 222  *        Add paths to the given joinrel for given pair of joining relations. The
 223  *        SpecialJoinInfo provides details about the join and the restrictlist
 224  *        contains the join clauses and the other clauses applicable for given pair
 225  *        of the joining relations.
 226  */
 227 static void
 228 populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
 229                                                         RelOptInfo *rel2, RelOptInfo *joinrel,
 230                                                         SpecialJoinInfo *sjinfo, List *restrictlist)
 231 {
 232         /*
 233          * Consider paths using each rel as both outer and inner.  Depending on
 234          * the join type, a provably empty outer or inner rel might mean the join
 235          * is provably empty too; in which case throw away any previously computed
 236          * paths and mark the join as dummy.  (We do it this way since it's
 237          * conceivable that dummy-ness of a multi-element join might only be
 238          * noticeable for certain construction paths.)
 239          *
 240          * Also, a provably constant-false join restriction typically means that
 241          * we can skip evaluating one or both sides of the join.  We do this by
 242          * marking the appropriate rel as dummy.  For outer joins, a
 243          * constant-false restriction that is pushed down still means the whole
 244          * join is dummy, while a non-pushed-down one means that no inner rows
 245          * will join so we can treat the inner rel as dummy.
 246          *
 247          * We need only consider the jointypes that appear in join_info_list, plus
 248          * JOIN_INNER.
 249          */
 250         switch (sjinfo->jointype)
 251         {
 252                 case JOIN_INNER:
 253                         if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 254                                 restriction_is_constant_false(restrictlist, joinrel, false))
 255                         {
 256                                 mark_dummy_rel(joinrel);
 257                                 break;
 258                         }
 259                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 260                                                                  JOIN_INNER, sjinfo,
 261                                                                  restrictlist);
 262                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 263                                                                  JOIN_INNER, sjinfo,
 264                                                                  restrictlist);
 265                         break;
 266                 case JOIN_LEFT:
 267                         if (is_dummy_rel(rel1) ||
 268                                 restriction_is_constant_false(restrictlist, joinrel, true))
 269                         {
 270                                 mark_dummy_rel(joinrel);
 271                                 break;
 272                         }
 273                         if (restriction_is_constant_false(restrictlist, joinrel, false) &&
 274                                 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
 275                                 mark_dummy_rel(rel2);
 276                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 277                                                                  JOIN_LEFT, sjinfo,
 278                                                                  restrictlist);
 279                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 280                                                                  JOIN_RIGHT, sjinfo,
 281                                                                  restrictlist);
 282                         break;
 283                 case JOIN_FULL:
 284                         if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
 285                                 restriction_is_constant_false(restrictlist, joinrel, true))
 286                         {
 287                                 mark_dummy_rel(joinrel);
 288                                 break;
 289                         }
 290                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 291                                                                  JOIN_FULL, sjinfo,
 292                                                                  restrictlist);
 293                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 294                                                                  JOIN_FULL, sjinfo,
 295                                                                  restrictlist);
 296
 297                         /*
 298                          * If there are join quals that aren't mergeable or hashable, we
 299                          * may not be able to build any valid plan.  Complain here so that
 300                          * we can give a somewhat-useful error message.  (Since we have no
 301                          * flexibility of planning for a full join, there's no chance of
 302                          * succeeding later with another pair of input rels.)
 303                          */
 304                         if (joinrel->pathlist == NIL)
 305                                 ereport(ERROR,
 306                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 307                                                  errmsg("FULL JOIN is only supported with merge-joinable or hash-joinable join conditions")));
 308                         break;
 309                 case JOIN_SEMI:
 310
 311                         /*
 312                          * We might have a normal semijoin, or a case where we don't have
 313                          * enough rels to do the semijoin but can unique-ify the RHS and
 314                          * then do an innerjoin (see comments in join_is_legal).  In the
 315                          * latter case we can't apply JOIN_SEMI joining.
 316                          */
 317                         if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
 318                                 bms_is_subset(sjinfo->min_righthand, rel2->relids))
 319                         {
 320                                 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 321                                         restriction_is_constant_false(restrictlist, joinrel, false))
 322                                 {
 323                                         mark_dummy_rel(joinrel);
 324                                         break;
 325                                 }
 326                                 add_paths_to_joinrel(root, joinrel, rel1, rel2,
 327                                                                          JOIN_SEMI, sjinfo,
 328                                                                          restrictlist);
 329                         }
 330
 331                         /*
 332                          * If we know how to unique-ify the RHS and one input rel is
 333                          * exactly the RHS (not a superset) we can consider unique-ifying
 334                          * it and then doing a regular join.  (The create_unique_path
 335                          * check here is probably redundant with what join_is_legal did,
 336                          * but if so the check is cheap because it's cached.  So test
 337                          * anyway to be sure.)
 338                          */
 339                         if (bms_equal(sjinfo->syn_righthand, rel2->relids) &&
 340                                 create_unique_path(root, rel2, rel2->cheapest_total_path,
 341                                                                    sjinfo) != NULL)
 342                         {
 343                                 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 344                                         restriction_is_constant_false(restrictlist, joinrel, false))
 345                                 {
 346                                         mark_dummy_rel(joinrel);
 347                                         break;
 348                                 }
 349                                 add_paths_to_joinrel(root, joinrel, rel1, rel2,
 350                                                                          JOIN_UNIQUE_INNER, sjinfo,
 351                                                                          restrictlist);
 352                                 add_paths_to_joinrel(root, joinrel, rel2, rel1,
 353                                                                          JOIN_UNIQUE_OUTER, sjinfo,
 354                                                                          restrictlist);
 355                         }
 356                         break;
 357                 case JOIN_ANTI:
 358                         if (is_dummy_rel(rel1) ||
 359                                 restriction_is_constant_false(restrictlist, joinrel, true))
 360                         {
 361                                 mark_dummy_rel(joinrel);
 362                                 break;
 363                         }
 364                         if (restriction_is_constant_false(restrictlist, joinrel, false) &&
 365                                 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
 366                                 mark_dummy_rel(rel2);
 367                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 368                                                                  JOIN_ANTI, sjinfo,
 369                                                                  restrictlist);
 370                         break;
 371                 default:
 372                         /* other values not expected here */
 373                         elog(ERROR, "unrecognized join type: %d", (int) sjinfo->jointype);
 374                         break;
 375         }
 376
 377         /* Apply partitionwise join technique, if possible. */
 378         try_partitionwise_join(root, rel1, rel2, joinrel, sjinfo, restrictlist);
 379 }