make_join_rel.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * make_join_rel.c
   4  *        Routines copied from PostgreSQL core distribution.
   5  *
   6  * src/backend/optimizer/path/joinrels.c
   7  *     make_join_rel()
   8  *
   9  * Portions Copyright (c) 2013-2014, 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
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15
  16 /*
  17  * make_join_rel
  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.)
  23  *
  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
  26  * turned into joins.
  27  */
  28 static double
  29 adjust_rows(double rows, RowsHint *hint)
  30 {
  31         double          result = 0.0;   /* keep compiler quiet */
  32
  33         if (hint->value_type == RVT_ABSOLUTE)
  34                 result = hint->rows;
  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;
  41         else
  42                 Assert(false);  /* unrecognized rows value type */
  43
  44         hint->base.state = HINT_STATE_USED;
  45         if (result < 1.0)
  46                 ereport(WARNING,
  47                                 (errmsg("Force estimate to be at least one row, to avoid possible divide-by-zero when interpolating costs : %s",
  48                                         hint->base.hint_str)));
  49         result = clamp_row_est(result);
  50         elog(DEBUG1, "adjusted rows %d to %d", (int) rows, (int) result);
  51
  52         return result;
  53 }
  54
  55 RelOptInfo *
  56 make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
  57 {
  58         Relids          joinrelids;
  59         SpecialJoinInfo *sjinfo;
  60         bool            reversed;
  61         SpecialJoinInfo sjinfo_data;
  62         RelOptInfo *joinrel;
  63         List       *restrictlist;
  64
  65         /* We should never try to join two overlapping sets of rels. */
  66         Assert(!bms_overlap(rel1->relids, rel2->relids));
  67
  68         /* Construct Relids set that identifies the joinrel. */
  69         joinrelids = bms_union(rel1->relids, rel2->relids);
  70
  71         /* Check validity and determine join type. */
  72         if (!join_is_legal(root, rel1, rel2, joinrelids,
  73                                            &sjinfo, &reversed))
  74         {
  75                 /* invalid join path */
  76                 bms_free(joinrelids);
  77                 return NULL;
  78         }
  79
  80         /* Swap rels if needed to match the join info. */
  81         if (reversed)
  82         {
  83                 RelOptInfo *trel = rel1;
  84
  85                 rel1 = rel2;
  86                 rel2 = trel;
  87         }
  88
  89         /*
  90          * If it's a plain inner join, then we won't have found anything in
  91          * join_info_list.  Make up a SpecialJoinInfo so that selectivity
  92          * estimation functions will know what's being joined.
  93          */
  94         if (sjinfo == NULL)
  95         {
  96                 sjinfo = &sjinfo_data;
  97                 sjinfo->type = T_SpecialJoinInfo;
  98                 sjinfo->min_lefthand = rel1->relids;
  99                 sjinfo->min_righthand = rel2->relids;
 100                 sjinfo->syn_lefthand = rel1->relids;
 101                 sjinfo->syn_righthand = rel2->relids;
 102                 sjinfo->jointype = JOIN_INNER;
 103                 /* we don't bother trying to make the remaining fields valid */
 104                 sjinfo->lhs_strict = false;
 105                 sjinfo->delay_upper_joins = false;
 106                 sjinfo->join_quals = NIL;
 107         }
 108
 109         /*
 110          * Find or build the join RelOptInfo, and compute the restrictlist that
 111          * goes with this particular joining.
 112          */
 113         joinrel = build_join_rel(root, joinrelids, rel1, rel2, sjinfo,
 114                                                          &restrictlist);
 115
 116         /* !!! START: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
 117         {
 118                 RowsHint   *rows_hint = NULL;
 119                 int                     i;
 120                 RowsHint   *justforme = NULL;
 121                 RowsHint   *domultiply = NULL;
 122
 123                 /* Search for applicable rows hint for this join node */
 124                 for (i = 0; i < current_hint->num_hints[HINT_TYPE_ROWS]; i++)
 125                 {
 126                         rows_hint = current_hint->rows_hints[i];
 127
 128                         /*
 129                          * Skip this rows_hint if it is invalid from the first or it
 130                          * doesn't target any join rels.
 131                          */
 132                         if (!rows_hint->joinrelids ||
 133                                 rows_hint->base.state == HINT_STATE_ERROR)
 134                                 continue;
 135
 136                         if (bms_equal(joinrelids, rows_hint->joinrelids))
 137                         {
 138                                 /*
 139                                  * This joinrel is just the target of this rows_hint, so tweak
 140                                  * rows estimation according to the hint.
 141                                  */
 142                                 justforme = rows_hint;
 143                         }
 144                         else if (!(bms_is_subset(rows_hint->joinrelids, rel1->relids) ||
 145                                            bms_is_subset(rows_hint->joinrelids, rel2->relids)) &&
 146                                          bms_is_subset(rows_hint->joinrelids, joinrelids) &&
 147                                          rows_hint->value_type == RVT_MULTI)
 148                         {
 149                                 /*
 150                                  * If the rows_hint's target relids is not a subset of both of
 151                                  * component rels and is a subset of this joinrel, ths hint's
 152                                  * targets spread over both component rels. This menas that
 153                                  * this hint has been never applied so far and this joinrel is
 154                                  * the first (and only) chance to fire in current join tree.
 155                                  * Only the multiplication hint has the cumulative nature so we
 156                                  * apply only RVT_MULTI in this way.
 157                                  */
 158                                 domultiply = rows_hint;
 159                         }
 160                 }
 161
 162                 if (justforme)
 163                 {
 164                         /*
 165                          * If a hint just for me is found, no other adjust method is
 166                          * useles, but this cannot be more than twice becuase this joinrel
 167                          * is already adjusted by this hint.
 168                          */
 169                         if (justforme->base.state == HINT_STATE_NOTUSED)
 170                                 joinrel->rows = adjust_rows(joinrel->rows, justforme);
 171                 }
 172                 else
 173                 {
 174                         if (domultiply)
 175                         {
 176                                 /*
 177                                  * If we have multiple routes up to this joinrel which are not
 178                                  * applicable this hint, this multiply hint will applied more
 179                                  * than twice. But there's no means to know of that,
 180                                  * re-estimate the row number of this joinrel always just
 181                                  * before applying the hint. This is a bit different from
 182                                  * normal planner behavior but it doesn't harm so much.
 183                                  */
 184                                 set_joinrel_size_estimates(root, joinrel, rel1, rel2, sjinfo,
 185                                                                                    restrictlist);
 186
 187                                 joinrel->rows = adjust_rows(joinrel->rows, domultiply);
 188                         }
 189
 190                 }
 191         }
 192         /* !!! END: HERE IS THE PART WHICH ADDED FOR PG_HINT_PLAN !!! */
 193
 194         /*
 195          * If we've already proven this join is empty, we needn't consider any
 196          * more paths for it.
 197          */
 198         if (is_dummy_rel(joinrel))
 199         {
 200                 bms_free(joinrelids);
 201                 return joinrel;
 202         }
 203
 204         /*
 205          * Consider paths using each rel as both outer and inner.  Depending on
 206          * the join type, a provably empty outer or inner rel might mean the join
 207          * is provably empty too; in which case throw away any previously computed
 208          * paths and mark the join as dummy.  (We do it this way since it's
 209          * conceivable that dummy-ness of a multi-element join might only be
 210          * noticeable for certain construction paths.)
 211          *
 212          * Also, a provably constant-false join restriction typically means that
 213          * we can skip evaluating one or both sides of the join.  We do this by
 214          * marking the appropriate rel as dummy.  For outer joins, a
 215          * constant-false restriction that is pushed down still means the whole
 216          * join is dummy, while a non-pushed-down one means that no inner rows
 217          * will join so we can treat the inner rel as dummy.
 218          *
 219          * We need only consider the jointypes that appear in join_info_list, plus
 220          * JOIN_INNER.
 221          */
 222         switch (sjinfo->jointype)
 223         {
 224                 case JOIN_INNER:
 225                         if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 226                                 restriction_is_constant_false(restrictlist, false))
 227                         {
 228                                 mark_dummy_rel(joinrel);
 229                                 break;
 230                         }
 231                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 232                                                                  JOIN_INNER, sjinfo,
 233                                                                  restrictlist);
 234                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 235                                                                  JOIN_INNER, sjinfo,
 236                                                                  restrictlist);
 237                         break;
 238                 case JOIN_LEFT:
 239                         if (is_dummy_rel(rel1) ||
 240                                 restriction_is_constant_false(restrictlist, true))
 241                         {
 242                                 mark_dummy_rel(joinrel);
 243                                 break;
 244                         }
 245                         if (restriction_is_constant_false(restrictlist, false) &&
 246                                 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
 247                                 mark_dummy_rel(rel2);
 248                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 249                                                                  JOIN_LEFT, sjinfo,
 250                                                                  restrictlist);
 251                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 252                                                                  JOIN_RIGHT, sjinfo,
 253                                                                  restrictlist);
 254                         break;
 255                 case JOIN_FULL:
 256                         if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
 257                                 restriction_is_constant_false(restrictlist, true))
 258                         {
 259                                 mark_dummy_rel(joinrel);
 260                                 break;
 261                         }
 262                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 263                                                                  JOIN_FULL, sjinfo,
 264                                                                  restrictlist);
 265                         add_paths_to_joinrel(root, joinrel, rel2, rel1,
 266                                                                  JOIN_FULL, sjinfo,
 267                                                                  restrictlist);
 268
 269                         /*
 270                          * If there are join quals that aren't mergeable or hashable, we
 271                          * may not be able to build any valid plan.  Complain here so that
 272                          * we can give a somewhat-useful error message.  (Since we have no
 273                          * flexibility of planning for a full join, there's no chance of
 274                          * succeeding later with another pair of input rels.)
 275                          */
 276                         if (joinrel->pathlist == NIL)
 277                                 ereport(ERROR,
 278                                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 279                                                  errmsg("FULL JOIN is only supported with merge-joinable or hash-joinable join conditions")));
 280                         break;
 281                 case JOIN_SEMI:
 282
 283                         /*
 284                          * We might have a normal semijoin, or a case where we don't have
 285                          * enough rels to do the semijoin but can unique-ify the RHS and
 286                          * then do an innerjoin (see comments in join_is_legal).  In the
 287                          * latter case we can't apply JOIN_SEMI joining.
 288                          */
 289                         if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
 290                                 bms_is_subset(sjinfo->min_righthand, rel2->relids))
 291                         {
 292                                 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 293                                         restriction_is_constant_false(restrictlist, false))
 294                                 {
 295                                         mark_dummy_rel(joinrel);
 296                                         break;
 297                                 }
 298                                 add_paths_to_joinrel(root, joinrel, rel1, rel2,
 299                                                                          JOIN_SEMI, sjinfo,
 300                                                                          restrictlist);
 301                         }
 302
 303                         /*
 304                          * If we know how to unique-ify the RHS and one input rel is
 305                          * exactly the RHS (not a superset) we can consider unique-ifying
 306                          * it and then doing a regular join.  (The create_unique_path
 307                          * check here is probably redundant with what join_is_legal did,
 308                          * but if so the check is cheap because it's cached.  So test
 309                          * anyway to be sure.)
 310                          */
 311                         if (bms_equal(sjinfo->syn_righthand, rel2->relids) &&
 312                                 create_unique_path(root, rel2, rel2->cheapest_total_path,
 313                                                                    sjinfo) != NULL)
 314                         {
 315                                 if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
 316                                         restriction_is_constant_false(restrictlist, false))
 317                                 {
 318                                         mark_dummy_rel(joinrel);
 319                                         break;
 320                                 }
 321                                 add_paths_to_joinrel(root, joinrel, rel1, rel2,
 322                                                                          JOIN_UNIQUE_INNER, sjinfo,
 323                                                                          restrictlist);
 324                                 add_paths_to_joinrel(root, joinrel, rel2, rel1,
 325                                                                          JOIN_UNIQUE_OUTER, sjinfo,
 326                                                                          restrictlist);
 327                         }
 328                         break;
 329                 case JOIN_ANTI:
 330                         if (is_dummy_rel(rel1) ||
 331                                 restriction_is_constant_false(restrictlist, true))
 332                         {
 333                                 mark_dummy_rel(joinrel);
 334                                 break;
 335                         }
 336                         if (restriction_is_constant_false(restrictlist, false) &&
 337                                 bms_is_subset(rel2->relids, sjinfo->syn_righthand))
 338                                 mark_dummy_rel(rel2);
 339                         add_paths_to_joinrel(root, joinrel, rel1, rel2,
 340                                                                  JOIN_ANTI, sjinfo,
 341                                                                  restrictlist);
 342                         break;
 343                 default:
 344                         /* other values not expected here */
 345                         elog(ERROR, "unrecognized join type: %d", (int) sjinfo->jointype);
 346                         break;
 347         }
 348
 349         bms_free(joinrelids);
 350
 351         return joinrel;
 352 }