granicus.if.org Git - postgresql/blob - src/backend/optimizer/path/equivclass.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * equivclass.c
   4  *        Routines for managing EquivalenceClasses
   5  *
   6  * See src/backend/optimizer/README for discussion of EquivalenceClasses.
   7  *
   8  *
   9  * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
  10  * Portions Copyright (c) 1994, Regents of the University of California
  11  *
  12  * IDENTIFICATION
  13  *        src/backend/optimizer/path/equivclass.c
  14  *
  15  *-------------------------------------------------------------------------
  16  */
  17 #include "postgres.h"
  18
  19 #include <limits.h>
  20
  21 #include "access/stratnum.h"
  22 #include "catalog/pg_type.h"
  23 #include "nodes/makefuncs.h"
  24 #include "nodes/nodeFuncs.h"
  25 #include "optimizer/appendinfo.h"
  26 #include "optimizer/clauses.h"
  27 #include "optimizer/optimizer.h"
  28 #include "optimizer/pathnode.h"
  29 #include "optimizer/paths.h"
  30 #include "optimizer/planmain.h"
  31 #include "optimizer/restrictinfo.h"
  32 #include "utils/lsyscache.h"
  33
  34
  35 static EquivalenceMember *add_eq_member(EquivalenceClass *ec,
  36                           Expr *expr, Relids relids, Relids nullable_relids,
  37                           bool is_child, Oid datatype);
  38 static void generate_base_implied_equalities_const(PlannerInfo *root,
  39                                                                            EquivalenceClass *ec);
  40 static void generate_base_implied_equalities_no_const(PlannerInfo *root,
  41                                                                                   EquivalenceClass *ec);
  42 static void generate_base_implied_equalities_broken(PlannerInfo *root,
  43                                                                                 EquivalenceClass *ec);
  44 static List *generate_join_implied_equalities_normal(PlannerInfo *root,
  45                                                                                 EquivalenceClass *ec,
  46                                                                                 Relids join_relids,
  47                                                                                 Relids outer_relids,
  48                                                                                 Relids inner_relids);
  49 static List *generate_join_implied_equalities_broken(PlannerInfo *root,
  50                                                                                 EquivalenceClass *ec,
  51                                                                                 Relids nominal_join_relids,
  52                                                                                 Relids outer_relids,
  53                                                                                 Relids nominal_inner_relids,
  54                                                                                 RelOptInfo *inner_rel);
  55 static Oid select_equality_operator(EquivalenceClass *ec,
  56                                                  Oid lefttype, Oid righttype);
  57 static RestrictInfo *create_join_clause(PlannerInfo *root,
  58                                    EquivalenceClass *ec, Oid opno,
  59                                    EquivalenceMember *leftem,
  60                                    EquivalenceMember *rightem,
  61                                    EquivalenceClass *parent_ec);
  62 static bool reconsider_outer_join_clause(PlannerInfo *root,
  63                                                          RestrictInfo *rinfo,
  64                                                          bool outer_on_left);
  65 static bool reconsider_full_join_clause(PlannerInfo *root,
  66                                                         RestrictInfo *rinfo);
  67
  68
  69 /*
  70  * process_equivalence
  71  *        The given clause has a mergejoinable operator and can be applied without
  72  *        any delay by an outer join, so its two sides can be considered equal
  73  *        anywhere they are both computable; moreover that equality can be
  74  *        extended transitively.  Record this knowledge in the EquivalenceClass
  75  *        data structure, if applicable.  Returns true if successful, false if not
  76  *        (in which case caller should treat the clause as ordinary, not an
  77  *        equivalence).
  78  *
  79  * In some cases, although we cannot convert a clause into EquivalenceClass
  80  * knowledge, we can still modify it to a more useful form than the original.
  81  * Then, *p_restrictinfo will be replaced by a new RestrictInfo, which is what
  82  * the caller should use for further processing.
  83  *
  84  * If below_outer_join is true, then the clause was found below the nullable
  85  * side of an outer join, so its sides might validly be both NULL rather than
  86  * strictly equal.  We can still deduce equalities in such cases, but we take
  87  * care to mark an EquivalenceClass if it came from any such clauses.  Also,
  88  * we have to check that both sides are either pseudo-constants or strict
  89  * functions of Vars, else they might not both go to NULL above the outer
  90  * join.  (This is the main reason why we need a failure return.  It's more
  91  * convenient to check this case here than at the call sites...)
  92  *
  93  * We also reject proposed equivalence clauses if they contain leaky functions
  94  * and have security_level above zero.  The EC evaluation rules require us to
  95  * apply certain tests at certain joining levels, and we can't tolerate
  96  * delaying any test on security_level grounds.  By rejecting candidate clauses
  97  * that might require security delays, we ensure it's safe to apply an EC
  98  * clause as soon as it's supposed to be applied.
  99  *
 100  * On success return, we have also initialized the clause's left_ec/right_ec
 101  * fields to point to the EquivalenceClass representing it.  This saves lookup
 102  * effort later.
 103  *
 104  * Note: constructing merged EquivalenceClasses is a standard UNION-FIND
 105  * problem, for which there exist better data structures than simple lists.
 106  * If this code ever proves to be a bottleneck then it could be sped up ---
 107  * but for now, simple is beautiful.
 108  *
 109  * Note: this is only called during planner startup, not during GEQO
 110  * exploration, so we need not worry about whether we're in the right
 111  * memory context.
 112  */
 113 bool
 114 process_equivalence(PlannerInfo *root,
 115                                         RestrictInfo **p_restrictinfo,
 116                                         bool below_outer_join)
 117 {
 118         RestrictInfo *restrictinfo = *p_restrictinfo;
 119         Expr       *clause = restrictinfo->clause;
 120         Oid                     opno,
 121                                 collation,
 122                                 item1_type,
 123                                 item2_type;
 124         Expr       *item1;
 125         Expr       *item2;
 126         Relids          item1_relids,
 127                                 item2_relids,
 128                                 item1_nullable_relids,
 129                                 item2_nullable_relids;
 130         List       *opfamilies;
 131         EquivalenceClass *ec1,
 132                            *ec2;
 133         EquivalenceMember *em1,
 134                            *em2;
 135         ListCell   *lc1;
 136
 137         /* Should not already be marked as having generated an eclass */
 138         Assert(restrictinfo->left_ec == NULL);
 139         Assert(restrictinfo->right_ec == NULL);
 140
 141         /* Reject if it is potentially postponable by security considerations */
 142         if (restrictinfo->security_level > 0 && !restrictinfo->leakproof)
 143                 return false;
 144
 145         /* Extract info from given clause */
 146         Assert(is_opclause(clause));
 147         opno = ((OpExpr *) clause)->opno;
 148         collation = ((OpExpr *) clause)->inputcollid;
 149         item1 = (Expr *) get_leftop(clause);
 150         item2 = (Expr *) get_rightop(clause);
 151         item1_relids = restrictinfo->left_relids;
 152         item2_relids = restrictinfo->right_relids;
 153
 154         /*
 155          * Ensure both input expressions expose the desired collation (their types
 156          * should be OK already); see comments for canonicalize_ec_expression.
 157          */
 158         item1 = canonicalize_ec_expression(item1,
 159                                                                            exprType((Node *) item1),
 160                                                                            collation);
 161         item2 = canonicalize_ec_expression(item2,
 162                                                                            exprType((Node *) item2),
 163                                                                            collation);
 164
 165         /*
 166          * Clauses of the form X=X cannot be translated into EquivalenceClasses.
 167          * We'd either end up with a single-entry EC, losing the knowledge that
 168          * the clause was present at all, or else make an EC with duplicate
 169          * entries, causing other issues.
 170          */
 171         if (equal(item1, item2))
 172         {
 173                 /*
 174                  * If the operator is strict, then the clause can be treated as just
 175                  * "X IS NOT NULL".  (Since we know we are considering a top-level
 176                  * qual, we can ignore the difference between FALSE and NULL results.)
 177                  * It's worth making the conversion because we'll typically get a much
 178                  * better selectivity estimate than we would for X=X.
 179                  *
 180                  * If the operator is not strict, we can't be sure what it will do
 181                  * with NULLs, so don't attempt to optimize it.
 182                  */
 183                 set_opfuncid((OpExpr *) clause);
 184                 if (func_strict(((OpExpr *) clause)->opfuncid))
 185                 {
 186                         NullTest   *ntest = makeNode(NullTest);
 187
 188                         ntest->arg = item1;
 189                         ntest->nulltesttype = IS_NOT_NULL;
 190                         ntest->argisrow = false;        /* correct even if composite arg */
 191                         ntest->location = -1;
 192
 193                         *p_restrictinfo =
 194                                 make_restrictinfo((Expr *) ntest,
 195                                                                   restrictinfo->is_pushed_down,
 196                                                                   restrictinfo->outerjoin_delayed,
 197                                                                   restrictinfo->pseudoconstant,
 198                                                                   restrictinfo->security_level,
 199                                                                   NULL,
 200                                                                   restrictinfo->outer_relids,
 201                                                                   restrictinfo->nullable_relids);
 202                 }
 203                 return false;
 204         }
 205
 206         /*
 207          * If below outer join, check for strictness, else reject.
 208          */
 209         if (below_outer_join)
 210         {
 211                 if (!bms_is_empty(item1_relids) &&
 212                         contain_nonstrict_functions((Node *) item1))
 213                         return false;           /* LHS is non-strict but not constant */
 214                 if (!bms_is_empty(item2_relids) &&
 215                         contain_nonstrict_functions((Node *) item2))
 216                         return false;           /* RHS is non-strict but not constant */
 217         }
 218
 219         /* Calculate nullable-relid sets for each side of the clause */
 220         item1_nullable_relids = bms_intersect(item1_relids,
 221                                                                                   restrictinfo->nullable_relids);
 222         item2_nullable_relids = bms_intersect(item2_relids,
 223                                                                                   restrictinfo->nullable_relids);
 224
 225         /*
 226          * We use the declared input types of the operator, not exprType() of the
 227          * inputs, as the nominal datatypes for opfamily lookup.  This presumes
 228          * that btree operators are always registered with amoplefttype and
 229          * amoprighttype equal to their declared input types.  We will need this
 230          * info anyway to build EquivalenceMember nodes, and by extracting it now
 231          * we can use type comparisons to short-circuit some equal() tests.
 232          */
 233         op_input_types(opno, &item1_type, &item2_type);
 234
 235         opfamilies = restrictinfo->mergeopfamilies;
 236
 237         /*
 238          * Sweep through the existing EquivalenceClasses looking for matches to
 239          * item1 and item2.  These are the possible outcomes:
 240          *
 241          * 1. We find both in the same EC.  The equivalence is already known, so
 242          * there's nothing to do.
 243          *
 244          * 2. We find both in different ECs.  Merge the two ECs together.
 245          *
 246          * 3. We find just one.  Add the other to its EC.
 247          *
 248          * 4. We find neither.  Make a new, two-entry EC.
 249          *
 250          * Note: since all ECs are built through this process or the similar
 251          * search in get_eclass_for_sort_expr(), it's impossible that we'd match
 252          * an item in more than one existing nonvolatile EC.  So it's okay to stop
 253          * at the first match.
 254          */
 255         ec1 = ec2 = NULL;
 256         em1 = em2 = NULL;
 257         foreach(lc1, root->eq_classes)
 258         {
 259                 EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
 260                 ListCell   *lc2;
 261
 262                 /* Never match to a volatile EC */
 263                 if (cur_ec->ec_has_volatile)
 264                         continue;
 265
 266                 /*
 267                  * The collation has to match; check this first since it's cheaper
 268                  * than the opfamily comparison.
 269                  */
 270                 if (collation != cur_ec->ec_collation)
 271                         continue;
 272
 273                 /*
 274                  * A "match" requires matching sets of btree opfamilies.  Use of
 275                  * equal() for this test has implications discussed in the comments
 276                  * for get_mergejoin_opfamilies().
 277                  */
 278                 if (!equal(opfamilies, cur_ec->ec_opfamilies))
 279                         continue;
 280
 281                 foreach(lc2, cur_ec->ec_members)
 282                 {
 283                         EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
 284
 285                         Assert(!cur_em->em_is_child);   /* no children yet */
 286
 287                         /*
 288                          * If below an outer join, don't match constants: they're not as
 289                          * constant as they look.
 290                          */
 291                         if ((below_outer_join || cur_ec->ec_below_outer_join) &&
 292                                 cur_em->em_is_const)
 293                                 continue;
 294
 295                         if (!ec1 &&
 296                                 item1_type == cur_em->em_datatype &&
 297                                 equal(item1, cur_em->em_expr))
 298                         {
 299                                 ec1 = cur_ec;
 300                                 em1 = cur_em;
 301                                 if (ec2)
 302                                         break;
 303                         }
 304
 305                         if (!ec2 &&
 306                                 item2_type == cur_em->em_datatype &&
 307                                 equal(item2, cur_em->em_expr))
 308                         {
 309                                 ec2 = cur_ec;
 310                                 em2 = cur_em;
 311                                 if (ec1)
 312                                         break;
 313                         }
 314                 }
 315
 316                 if (ec1 && ec2)
 317                         break;
 318         }
 319
 320         /* Sweep finished, what did we find? */
 321
 322         if (ec1 && ec2)
 323         {
 324                 /* If case 1, nothing to do, except add to sources */
 325                 if (ec1 == ec2)
 326                 {
 327                         ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
 328                         ec1->ec_below_outer_join |= below_outer_join;
 329                         ec1->ec_min_security = Min(ec1->ec_min_security,
 330                                                                            restrictinfo->security_level);
 331                         ec1->ec_max_security = Max(ec1->ec_max_security,
 332                                                                            restrictinfo->security_level);
 333                         /* mark the RI as associated with this eclass */
 334                         restrictinfo->left_ec = ec1;
 335                         restrictinfo->right_ec = ec1;
 336                         /* mark the RI as usable with this pair of EMs */
 337                         restrictinfo->left_em = em1;
 338                         restrictinfo->right_em = em2;
 339                         return true;
 340                 }
 341
 342                 /*
 343                  * Case 2: need to merge ec1 and ec2.  This should never happen after
 344                  * we've built any canonical pathkeys; if it did, those pathkeys might
 345                  * be rendered non-canonical by the merge.
 346                  */
 347                 if (root->canon_pathkeys != NIL)
 348                         elog(ERROR, "too late to merge equivalence classes");
 349
 350                 /*
 351                  * We add ec2's items to ec1, then set ec2's ec_merged link to point
 352                  * to ec1 and remove ec2 from the eq_classes list.  We cannot simply
 353                  * delete ec2 because that could leave dangling pointers in existing
 354                  * PathKeys.  We leave it behind with a link so that the merged EC can
 355                  * be found.
 356                  */
 357                 ec1->ec_members = list_concat(ec1->ec_members, ec2->ec_members);
 358                 ec1->ec_sources = list_concat(ec1->ec_sources, ec2->ec_sources);
 359                 ec1->ec_derives = list_concat(ec1->ec_derives, ec2->ec_derives);
 360                 ec1->ec_relids = bms_join(ec1->ec_relids, ec2->ec_relids);
 361                 ec1->ec_has_const |= ec2->ec_has_const;
 362                 /* can't need to set has_volatile */
 363                 ec1->ec_below_outer_join |= ec2->ec_below_outer_join;
 364                 ec1->ec_min_security = Min(ec1->ec_min_security,
 365                                                                    ec2->ec_min_security);
 366                 ec1->ec_max_security = Max(ec1->ec_max_security,
 367                                                                    ec2->ec_max_security);
 368                 ec2->ec_merged = ec1;
 369                 root->eq_classes = list_delete_ptr(root->eq_classes, ec2);
 370                 /* just to avoid debugging confusion w/ dangling pointers: */
 371                 ec2->ec_members = NIL;
 372                 ec2->ec_sources = NIL;
 373                 ec2->ec_derives = NIL;
 374                 ec2->ec_relids = NULL;
 375                 ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
 376                 ec1->ec_below_outer_join |= below_outer_join;
 377                 ec1->ec_min_security = Min(ec1->ec_min_security,
 378                                                                    restrictinfo->security_level);
 379                 ec1->ec_max_security = Max(ec1->ec_max_security,
 380                                                                    restrictinfo->security_level);
 381                 /* mark the RI as associated with this eclass */
 382                 restrictinfo->left_ec = ec1;
 383                 restrictinfo->right_ec = ec1;
 384                 /* mark the RI as usable with this pair of EMs */
 385                 restrictinfo->left_em = em1;
 386                 restrictinfo->right_em = em2;
 387         }
 388         else if (ec1)
 389         {
 390                 /* Case 3: add item2 to ec1 */
 391                 em2 = add_eq_member(ec1, item2, item2_relids, item2_nullable_relids,
 392                                                         false, item2_type);
 393                 ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
 394                 ec1->ec_below_outer_join |= below_outer_join;
 395                 ec1->ec_min_security = Min(ec1->ec_min_security,
 396                                                                    restrictinfo->security_level);
 397                 ec1->ec_max_security = Max(ec1->ec_max_security,
 398                                                                    restrictinfo->security_level);
 399                 /* mark the RI as associated with this eclass */
 400                 restrictinfo->left_ec = ec1;
 401                 restrictinfo->right_ec = ec1;
 402                 /* mark the RI as usable with this pair of EMs */
 403                 restrictinfo->left_em = em1;
 404                 restrictinfo->right_em = em2;
 405         }
 406         else if (ec2)
 407         {
 408                 /* Case 3: add item1 to ec2 */
 409                 em1 = add_eq_member(ec2, item1, item1_relids, item1_nullable_relids,
 410                                                         false, item1_type);
 411                 ec2->ec_sources = lappend(ec2->ec_sources, restrictinfo);
 412                 ec2->ec_below_outer_join |= below_outer_join;
 413                 ec2->ec_min_security = Min(ec2->ec_min_security,
 414                                                                    restrictinfo->security_level);
 415                 ec2->ec_max_security = Max(ec2->ec_max_security,
 416                                                                    restrictinfo->security_level);
 417                 /* mark the RI as associated with this eclass */
 418                 restrictinfo->left_ec = ec2;
 419                 restrictinfo->right_ec = ec2;
 420                 /* mark the RI as usable with this pair of EMs */
 421                 restrictinfo->left_em = em1;
 422                 restrictinfo->right_em = em2;
 423         }
 424         else
 425         {
 426                 /* Case 4: make a new, two-entry EC */
 427                 EquivalenceClass *ec = makeNode(EquivalenceClass);
 428
 429                 ec->ec_opfamilies = opfamilies;
 430                 ec->ec_collation = collation;
 431                 ec->ec_members = NIL;
 432                 ec->ec_sources = list_make1(restrictinfo);
 433                 ec->ec_derives = NIL;
 434                 ec->ec_relids = NULL;
 435                 ec->ec_has_const = false;
 436                 ec->ec_has_volatile = false;
 437                 ec->ec_below_outer_join = below_outer_join;
 438                 ec->ec_broken = false;
 439                 ec->ec_sortref = 0;
 440                 ec->ec_min_security = restrictinfo->security_level;
 441                 ec->ec_max_security = restrictinfo->security_level;
 442                 ec->ec_merged = NULL;
 443                 em1 = add_eq_member(ec, item1, item1_relids, item1_nullable_relids,
 444                                                         false, item1_type);
 445                 em2 = add_eq_member(ec, item2, item2_relids, item2_nullable_relids,
 446                                                         false, item2_type);
 447
 448                 root->eq_classes = lappend(root->eq_classes, ec);
 449
 450                 /* mark the RI as associated with this eclass */
 451                 restrictinfo->left_ec = ec;
 452                 restrictinfo->right_ec = ec;
 453                 /* mark the RI as usable with this pair of EMs */
 454                 restrictinfo->left_em = em1;
 455                 restrictinfo->right_em = em2;
 456         }
 457
 458         return true;
 459 }
 460
 461 /*
 462  * canonicalize_ec_expression
 463  *
 464  * This function ensures that the expression exposes the expected type and
 465  * collation, so that it will be equal() to other equivalence-class expressions
 466  * that it ought to be equal() to.
 467  *
 468  * The rule for datatypes is that the exposed type should match what it would
 469  * be for an input to an operator of the EC's opfamilies; which is usually
 470  * the declared input type of the operator, but in the case of polymorphic
 471  * operators no relabeling is wanted (compare the behavior of parse_coerce.c).
 472  * Expressions coming in from quals will generally have the right type
 473  * already, but expressions coming from indexkeys may not (because they are
 474  * represented without any explicit relabel in pg_index), and the same problem
 475  * occurs for sort expressions (because the parser is likewise cavalier about
 476  * putting relabels on them).  Such cases will be binary-compatible with the
 477  * real operators, so adding a RelabelType is sufficient.
 478  *
 479  * Also, the expression's exposed collation must match the EC's collation.
 480  * This is important because in comparisons like "foo < bar COLLATE baz",
 481  * only one of the expressions has the correct exposed collation as we receive
 482  * it from the parser.  Forcing both of them to have it ensures that all
 483  * variant spellings of such a construct behave the same.  Again, we can
 484  * stick on a RelabelType to force the right exposed collation.  (It might
 485  * work to not label the collation at all in EC members, but this is risky
 486  * since some parts of the system expect exprCollation() to deliver the
 487  * right answer for a sort key.)
 488  *
 489  * Note this code assumes that the expression has already been through
 490  * eval_const_expressions, so there are no CollateExprs and no redundant
 491  * RelabelTypes.
 492  */
 493 Expr *
 494 canonicalize_ec_expression(Expr *expr, Oid req_type, Oid req_collation)
 495 {
 496         Oid                     expr_type = exprType((Node *) expr);
 497
 498         /*
 499          * For a polymorphic-input-type opclass, just keep the same exposed type.
 500          * RECORD opclasses work like polymorphic-type ones for this purpose.
 501          */
 502         if (IsPolymorphicType(req_type) || req_type == RECORDOID)
 503                 req_type = expr_type;
 504
 505         /*
 506          * No work if the expression exposes the right type/collation already.
 507          */
 508         if (expr_type != req_type ||
 509                 exprCollation((Node *) expr) != req_collation)
 510         {
 511                 /*
 512                  * Strip any existing RelabelType, then add a new one if needed. This
 513                  * is to preserve the invariant of no redundant RelabelTypes.
 514                  *
 515                  * If we have to change the exposed type of the stripped expression,
 516                  * set typmod to -1 (since the new type may not have the same typmod
 517                  * interpretation).  If we only have to change collation, preserve the
 518                  * exposed typmod.
 519                  */
 520                 while (expr && IsA(expr, RelabelType))
 521                         expr = (Expr *) ((RelabelType *) expr)->arg;
 522
 523                 if (exprType((Node *) expr) != req_type)
 524                         expr = (Expr *) makeRelabelType(expr,
 525                                                                                         req_type,
 526                                                                                         -1,
 527                                                                                         req_collation,
 528                                                                                         COERCE_IMPLICIT_CAST);
 529                 else if (exprCollation((Node *) expr) != req_collation)
 530                         expr = (Expr *) makeRelabelType(expr,
 531                                                                                         req_type,
 532                                                                                         exprTypmod((Node *) expr),
 533                                                                                         req_collation,
 534                                                                                         COERCE_IMPLICIT_CAST);
 535         }
 536
 537         return expr;
 538 }
 539
 540 /*
 541  * add_eq_member - build a new EquivalenceMember and add it to an EC
 542  */
 543 static EquivalenceMember *
 544 add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
 545                           Relids nullable_relids, bool is_child, Oid datatype)
 546 {
 547         EquivalenceMember *em = makeNode(EquivalenceMember);
 548
 549         em->em_expr = expr;
 550         em->em_relids = relids;
 551         em->em_nullable_relids = nullable_relids;
 552         em->em_is_const = false;
 553         em->em_is_child = is_child;
 554         em->em_datatype = datatype;
 555
 556         if (bms_is_empty(relids))
 557         {
 558                 /*
 559                  * No Vars, assume it's a pseudoconstant.  This is correct for entries
 560                  * generated from process_equivalence(), because a WHERE clause can't
 561                  * contain aggregates or SRFs, and non-volatility was checked before
 562                  * process_equivalence() ever got called.  But
 563                  * get_eclass_for_sort_expr() has to work harder.  We put the tests
 564                  * there not here to save cycles in the equivalence case.
 565                  */
 566                 Assert(!is_child);
 567                 em->em_is_const = true;
 568                 ec->ec_has_const = true;
 569                 /* it can't affect ec_relids */
 570         }
 571         else if (!is_child)                     /* child members don't add to ec_relids */
 572         {
 573                 ec->ec_relids = bms_add_members(ec->ec_relids, relids);
 574         }
 575         ec->ec_members = lappend(ec->ec_members, em);
 576
 577         return em;
 578 }
 579
 580
 581 /*
 582  * get_eclass_for_sort_expr
 583  *        Given an expression and opfamily/collation info, find an existing
 584  *        equivalence class it is a member of; if none, optionally build a new
 585  *        single-member EquivalenceClass for it.
 586  *
 587  * expr is the expression, and nullable_relids is the set of base relids
 588  * that are potentially nullable below it.  We actually only care about
 589  * the set of such relids that are used in the expression; but for caller
 590  * convenience, we perform that intersection step here.  The caller need
 591  * only be sure that nullable_relids doesn't omit any nullable rels that
 592  * might appear in the expr.
 593  *
 594  * sortref is the SortGroupRef of the originating SortGroupClause, if any,
 595  * or zero if not.  (It should never be zero if the expression is volatile!)
 596  *
 597  * If rel is not NULL, it identifies a specific relation we're considering
 598  * a path for, and indicates that child EC members for that relation can be
 599  * considered.  Otherwise child members are ignored.  (Note: since child EC
 600  * members aren't guaranteed unique, a non-NULL value means that there could
 601  * be more than one EC that matches the expression; if so it's order-dependent
 602  * which one you get.  This is annoying but it only happens in corner cases,
 603  * so for now we live with just reporting the first match.  See also
 604  * generate_implied_equalities_for_column and match_pathkeys_to_index.)
 605  *
 606  * If create_it is true, we'll build a new EquivalenceClass when there is no
 607  * match.  If create_it is false, we just return NULL when no match.
 608  *
 609  * This can be used safely both before and after EquivalenceClass merging;
 610  * since it never causes merging it does not invalidate any existing ECs
 611  * or PathKeys.  However, ECs added after path generation has begun are
 612  * of limited usefulness, so usually it's best to create them beforehand.
 613  *
 614  * Note: opfamilies must be chosen consistently with the way
 615  * process_equivalence() would do; that is, generated from a mergejoinable
 616  * equality operator.  Else we might fail to detect valid equivalences,
 617  * generating poor (but not incorrect) plans.
 618  */
 619 EquivalenceClass *
 620 get_eclass_for_sort_expr(PlannerInfo *root,
 621                                                  Expr *expr,
 622                                                  Relids nullable_relids,
 623                                                  List *opfamilies,
 624                                                  Oid opcintype,
 625                                                  Oid collation,
 626                                                  Index sortref,
 627                                                  Relids rel,
 628                                                  bool create_it)
 629 {
 630         Relids          expr_relids;
 631         EquivalenceClass *newec;
 632         EquivalenceMember *newem;
 633         ListCell   *lc1;
 634         MemoryContext oldcontext;
 635
 636         /*
 637          * Ensure the expression exposes the correct type and collation.
 638          */
 639         expr = canonicalize_ec_expression(expr, opcintype, collation);
 640
 641         /*
 642          * Get the precise set of nullable relids appearing in the expression.
 643          */
 644         expr_relids = pull_varnos((Node *) expr);
 645         nullable_relids = bms_intersect(nullable_relids, expr_relids);
 646
 647         /*
 648          * Scan through the existing EquivalenceClasses for a match
 649          */
 650         foreach(lc1, root->eq_classes)
 651         {
 652                 EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
 653                 ListCell   *lc2;
 654
 655                 /*
 656                  * Never match to a volatile EC, except when we are looking at another
 657                  * reference to the same volatile SortGroupClause.
 658                  */
 659                 if (cur_ec->ec_has_volatile &&
 660                         (sortref == 0 || sortref != cur_ec->ec_sortref))
 661                         continue;
 662
 663                 if (collation != cur_ec->ec_collation)
 664                         continue;
 665                 if (!equal(opfamilies, cur_ec->ec_opfamilies))
 666                         continue;
 667
 668                 foreach(lc2, cur_ec->ec_members)
 669                 {
 670                         EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
 671
 672                         /*
 673                          * Ignore child members unless they match the request.
 674                          */
 675                         if (cur_em->em_is_child &&
 676                                 !bms_equal(cur_em->em_relids, rel))
 677                                 continue;
 678
 679                         /*
 680                          * If below an outer join, don't match constants: they're not as
 681                          * constant as they look.
 682                          */
 683                         if (cur_ec->ec_below_outer_join &&
 684                                 cur_em->em_is_const)
 685                                 continue;
 686
 687                         if (opcintype == cur_em->em_datatype &&
 688                                 equal(expr, cur_em->em_expr))
 689                                 return cur_ec;  /* Match! */
 690                 }
 691         }
 692
 693         /* No match; does caller want a NULL result? */
 694         if (!create_it)
 695                 return NULL;
 696
 697         /*
 698          * OK, build a new single-member EC
 699          *
 700          * Here, we must be sure that we construct the EC in the right context.
 701          */
 702         oldcontext = MemoryContextSwitchTo(root->planner_cxt);
 703
 704         newec = makeNode(EquivalenceClass);
 705         newec->ec_opfamilies = list_copy(opfamilies);
 706         newec->ec_collation = collation;
 707         newec->ec_members = NIL;
 708         newec->ec_sources = NIL;
 709         newec->ec_derives = NIL;
 710         newec->ec_relids = NULL;
 711         newec->ec_has_const = false;
 712         newec->ec_has_volatile = contain_volatile_functions((Node *) expr);
 713         newec->ec_below_outer_join = false;
 714         newec->ec_broken = false;
 715         newec->ec_sortref = sortref;
 716         newec->ec_min_security = UINT_MAX;
 717         newec->ec_max_security = 0;
 718         newec->ec_merged = NULL;
 719
 720         if (newec->ec_has_volatile && sortref == 0) /* should not happen */
 721                 elog(ERROR, "volatile EquivalenceClass has no sortref");
 722
 723         newem = add_eq_member(newec, copyObject(expr), expr_relids,
 724                                                   nullable_relids, false, opcintype);
 725
 726         /*
 727          * add_eq_member doesn't check for volatile functions, set-returning
 728          * functions, aggregates, or window functions, but such could appear in
 729          * sort expressions; so we have to check whether its const-marking was
 730          * correct.
 731          */
 732         if (newec->ec_has_const)
 733         {
 734                 if (newec->ec_has_volatile ||
 735                         expression_returns_set((Node *) expr) ||
 736                         contain_agg_clause((Node *) expr) ||
 737                         contain_window_function((Node *) expr))
 738                 {
 739                         newec->ec_has_const = false;
 740                         newem->em_is_const = false;
 741                 }
 742         }
 743
 744         root->eq_classes = lappend(root->eq_classes, newec);
 745
 746         MemoryContextSwitchTo(oldcontext);
 747
 748         return newec;
 749 }
 750
 751
 752 /*
 753  * generate_base_implied_equalities
 754  *        Generate any restriction clauses that we can deduce from equivalence
 755  *        classes.
 756  *
 757  * When an EC contains pseudoconstants, our strategy is to generate
 758  * "member = const1" clauses where const1 is the first constant member, for
 759  * every other member (including other constants).  If we are able to do this
 760  * then we don't need any "var = var" comparisons because we've successfully
 761  * constrained all the vars at their points of creation.  If we fail to
 762  * generate any of these clauses due to lack of cross-type operators, we fall
 763  * back to the "ec_broken" strategy described below.  (XXX if there are
 764  * multiple constants of different types, it's possible that we might succeed
 765  * in forming all the required clauses if we started from a different const
 766  * member; but this seems a sufficiently hokey corner case to not be worth
 767  * spending lots of cycles on.)
 768  *
 769  * For ECs that contain no pseudoconstants, we generate derived clauses
 770  * "member1 = member2" for each pair of members belonging to the same base
 771  * relation (actually, if there are more than two for the same base relation,
 772  * we only need enough clauses to link each to each other).  This provides
 773  * the base case for the recursion: each row emitted by a base relation scan
 774  * will constrain all computable members of the EC to be equal.  As each
 775  * join path is formed, we'll add additional derived clauses on-the-fly
 776  * to maintain this invariant (see generate_join_implied_equalities).
 777  *
 778  * If the opfamilies used by the EC do not provide complete sets of cross-type
 779  * equality operators, it is possible that we will fail to generate a clause
 780  * that must be generated to maintain the invariant.  (An example: given
 781  * "WHERE a.x = b.y AND b.y = a.z", the scheme breaks down if we cannot
 782  * generate "a.x = a.z" as a restriction clause for A.)  In this case we mark
 783  * the EC "ec_broken" and fall back to regurgitating its original source
 784  * RestrictInfos at appropriate times.  We do not try to retract any derived
 785  * clauses already generated from the broken EC, so the resulting plan could
 786  * be poor due to bad selectivity estimates caused by redundant clauses.  But
 787  * the correct solution to that is to fix the opfamilies ...
 788  *
 789  * Equality clauses derived by this function are passed off to
 790  * process_implied_equality (in plan/initsplan.c) to be inserted into the
 791  * restrictinfo datastructures.  Note that this must be called after initial
 792  * scanning of the quals and before Path construction begins.
 793  *
 794  * We make no attempt to avoid generating duplicate RestrictInfos here: we
 795  * don't search ec_sources for matches, nor put the created RestrictInfos
 796  * into ec_derives.  Doing so would require some slightly ugly changes in
 797  * initsplan.c's API, and there's no real advantage, because the clauses
 798  * generated here can't duplicate anything we will generate for joins anyway.
 799  */
 800 void
 801 generate_base_implied_equalities(PlannerInfo *root)
 802 {
 803         ListCell   *lc;
 804         Index           rti;
 805
 806         foreach(lc, root->eq_classes)
 807         {
 808                 EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
 809
 810                 Assert(ec->ec_merged == NULL);  /* else shouldn't be in list */
 811                 Assert(!ec->ec_broken); /* not yet anyway... */
 812
 813                 /* Single-member ECs won't generate any deductions */
 814                 if (list_length(ec->ec_members) <= 1)
 815                         continue;
 816
 817                 if (ec->ec_has_const)
 818                         generate_base_implied_equalities_const(root, ec);
 819                 else
 820                         generate_base_implied_equalities_no_const(root, ec);
 821
 822                 /* Recover if we failed to generate required derived clauses */
 823                 if (ec->ec_broken)
 824                         generate_base_implied_equalities_broken(root, ec);
 825         }
 826
 827         /*
 828          * This is also a handy place to mark base rels (which should all exist by
 829          * now) with flags showing whether they have pending eclass joins.
 830          */
 831         for (rti = 1; rti < root->simple_rel_array_size; rti++)
 832         {
 833                 RelOptInfo *brel = root->simple_rel_array[rti];
 834
 835                 if (brel == NULL)
 836                         continue;
 837
 838                 brel->has_eclass_joins = has_relevant_eclass_joinclause(root, brel);
 839         }
 840 }
 841
 842 /*
 843  * generate_base_implied_equalities when EC contains pseudoconstant(s)
 844  */
 845 static void
 846 generate_base_implied_equalities_const(PlannerInfo *root,
 847                                                                            EquivalenceClass *ec)
 848 {
 849         EquivalenceMember *const_em = NULL;
 850         ListCell   *lc;
 851
 852         /*
 853          * In the trivial case where we just had one "var = const" clause, push
 854          * the original clause back into the main planner machinery.  There is
 855          * nothing to be gained by doing it differently, and we save the effort to
 856          * re-build and re-analyze an equality clause that will be exactly
 857          * equivalent to the old one.
 858          */
 859         if (list_length(ec->ec_members) == 2 &&
 860                 list_length(ec->ec_sources) == 1)
 861         {
 862                 RestrictInfo *restrictinfo = (RestrictInfo *) linitial(ec->ec_sources);
 863
 864                 if (bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
 865                 {
 866                         distribute_restrictinfo_to_rels(root, restrictinfo);
 867                         return;
 868                 }
 869         }
 870
 871         /*
 872          * Find the constant member to use.  We prefer an actual constant to
 873          * pseudo-constants (such as Params), because the constraint exclusion
 874          * machinery might be able to exclude relations on the basis of generated
 875          * "var = const" equalities, but "var = param" won't work for that.
 876          */
 877         foreach(lc, ec->ec_members)
 878         {
 879                 EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
 880
 881                 if (cur_em->em_is_const)
 882                 {
 883                         const_em = cur_em;
 884                         if (IsA(cur_em->em_expr, Const))
 885                                 break;
 886                 }
 887         }
 888         Assert(const_em != NULL);
 889
 890         /* Generate a derived equality against each other member */
 891         foreach(lc, ec->ec_members)
 892         {
 893                 EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
 894                 Oid                     eq_op;
 895
 896                 Assert(!cur_em->em_is_child);   /* no children yet */
 897                 if (cur_em == const_em)
 898                         continue;
 899                 eq_op = select_equality_operator(ec,
 900                                                                                  cur_em->em_datatype,
 901                                                                                  const_em->em_datatype);
 902                 if (!OidIsValid(eq_op))
 903                 {
 904                         /* failed... */
 905                         ec->ec_broken = true;
 906                         break;
 907                 }
 908                 process_implied_equality(root, eq_op, ec->ec_collation,
 909                                                                  cur_em->em_expr, const_em->em_expr,
 910                                                                  bms_copy(ec->ec_relids),
 911                                                                  bms_union(cur_em->em_nullable_relids,
 912                                                                                    const_em->em_nullable_relids),
 913                                                                  ec->ec_min_security,
 914                                                                  ec->ec_below_outer_join,
 915                                                                  cur_em->em_is_const);
 916         }
 917 }
 918
 919 /*
 920  * generate_base_implied_equalities when EC contains no pseudoconstants
 921  */
 922 static void
 923 generate_base_implied_equalities_no_const(PlannerInfo *root,
 924                                                                                   EquivalenceClass *ec)
 925 {
 926         EquivalenceMember **prev_ems;
 927         ListCell   *lc;
 928
 929         /*
 930          * We scan the EC members once and track the last-seen member for each
 931          * base relation.  When we see another member of the same base relation,
 932          * we generate "prev_mem = cur_mem".  This results in the minimum number
 933          * of derived clauses, but it's possible that it will fail when a
 934          * different ordering would succeed.  XXX FIXME: use a UNION-FIND
 935          * algorithm similar to the way we build merged ECs.  (Use a list-of-lists
 936          * for each rel.)
 937          */
 938         prev_ems = (EquivalenceMember **)
 939                 palloc0(root->simple_rel_array_size * sizeof(EquivalenceMember *));
 940
 941         foreach(lc, ec->ec_members)
 942         {
 943                 EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
 944                 int                     relid;
 945
 946                 Assert(!cur_em->em_is_child);   /* no children yet */
 947                 if (!bms_get_singleton_member(cur_em->em_relids, &relid))
 948                         continue;
 949                 Assert(relid < root->simple_rel_array_size);
 950
 951                 if (prev_ems[relid] != NULL)
 952                 {
 953                         EquivalenceMember *prev_em = prev_ems[relid];
 954                         Oid                     eq_op;
 955
 956                         eq_op = select_equality_operator(ec,
 957                                                                                          prev_em->em_datatype,
 958                                                                                          cur_em->em_datatype);
 959                         if (!OidIsValid(eq_op))
 960                         {
 961                                 /* failed... */
 962                                 ec->ec_broken = true;
 963                                 break;
 964                         }
 965                         process_implied_equality(root, eq_op, ec->ec_collation,
 966                                                                          prev_em->em_expr, cur_em->em_expr,
 967                                                                          bms_copy(ec->ec_relids),
 968                                                                          bms_union(prev_em->em_nullable_relids,
 969                                                                                            cur_em->em_nullable_relids),
 970                                                                          ec->ec_min_security,
 971                                                                          ec->ec_below_outer_join,
 972                                                                          false);
 973                 }
 974                 prev_ems[relid] = cur_em;
 975         }
 976
 977         pfree(prev_ems);
 978
 979         /*
 980          * We also have to make sure that all the Vars used in the member clauses
 981          * will be available at any join node we might try to reference them at.
 982          * For the moment we force all the Vars to be available at all join nodes
 983          * for this eclass.  Perhaps this could be improved by doing some
 984          * pre-analysis of which members we prefer to join, but it's no worse than
 985          * what happened in the pre-8.3 code.
 986          */
 987         foreach(lc, ec->ec_members)
 988         {
 989                 EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
 990                 List       *vars = pull_var_clause((Node *) cur_em->em_expr,
 991                                                                                    PVC_RECURSE_AGGREGATES |
 992                                                                                    PVC_RECURSE_WINDOWFUNCS |
 993                                                                                    PVC_INCLUDE_PLACEHOLDERS);
 994
 995                 add_vars_to_targetlist(root, vars, ec->ec_relids, false);
 996                 list_free(vars);
 997         }
 998 }
 999
1000 /*
1001  * generate_base_implied_equalities cleanup after failure
1002  *
1003  * What we must do here is push any zero- or one-relation source RestrictInfos
1004  * of the EC back into the main restrictinfo datastructures.  Multi-relation
1005  * clauses will be regurgitated later by generate_join_implied_equalities().
1006  * (We do it this way to maintain continuity with the case that ec_broken
1007  * becomes set only after we've gone up a join level or two.)  However, for
1008  * an EC that contains constants, we can adopt a simpler strategy and just
1009  * throw back all the source RestrictInfos immediately; that works because
1010  * we know that such an EC can't become broken later.  (This rule justifies
1011  * ignoring ec_has_const ECs in generate_join_implied_equalities, even when
1012  * they are broken.)
1013  */
1014 static void
1015 generate_base_implied_equalities_broken(PlannerInfo *root,
1016                                                                                 EquivalenceClass *ec)
1017 {
1018         ListCell   *lc;
1019
1020         foreach(lc, ec->ec_sources)
1021         {
1022                 RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
1023
1024                 if (ec->ec_has_const ||
1025                         bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
1026                         distribute_restrictinfo_to_rels(root, restrictinfo);
1027         }
1028 }
1029
1030
1031 /*
1032  * generate_join_implied_equalities
1033  *        Generate any join clauses that we can deduce from equivalence classes.
1034  *
1035  * At a join node, we must enforce restriction clauses sufficient to ensure
1036  * that all equivalence-class members computable at that node are equal.
1037  * Since the set of clauses to enforce can vary depending on which subset
1038  * relations are the inputs, we have to compute this afresh for each join
1039  * relation pair.  Hence a fresh List of RestrictInfo nodes is built and
1040  * passed back on each call.
1041  *
1042  * In addition to its use at join nodes, this can be applied to generate
1043  * eclass-based join clauses for use in a parameterized scan of a base rel.
1044  * The reason for the asymmetry of specifying the inner rel as a RelOptInfo
1045  * and the outer rel by Relids is that this usage occurs before we have
1046  * built any join RelOptInfos.
1047  *
1048  * An annoying special case for parameterized scans is that the inner rel can
1049  * be an appendrel child (an "other rel").  In this case we must generate
1050  * appropriate clauses using child EC members.  add_child_rel_equivalences
1051  * must already have been done for the child rel.
1052  *
1053  * The results are sufficient for use in merge, hash, and plain nestloop join
1054  * methods.  We do not worry here about selecting clauses that are optimal
1055  * for use in a parameterized indexscan.  indxpath.c makes its own selections
1056  * of clauses to use, and if the ones we pick here are redundant with those,
1057  * the extras will be eliminated at createplan time, using the parent_ec
1058  * markers that we provide (see is_redundant_derived_clause()).
1059  *
1060  * Because the same join clauses are likely to be needed multiple times as
1061  * we consider different join paths, we avoid generating multiple copies:
1062  * whenever we select a particular pair of EquivalenceMembers to join,
1063  * we check to see if the pair matches any original clause (in ec_sources)
1064  * or previously-built clause (in ec_derives).  This saves memory and allows
1065  * re-use of information cached in RestrictInfos.
1066  *
1067  * join_relids should always equal bms_union(outer_relids, inner_rel->relids).
1068  * We could simplify this function's API by computing it internally, but in
1069  * most current uses, the caller has the value at hand anyway.
1070  */
1071 List *
1072 generate_join_implied_equalities(PlannerInfo *root,
1073                                                                  Relids join_relids,
1074                                                                  Relids outer_relids,
1075                                                                  RelOptInfo *inner_rel)
1076 {
1077         return generate_join_implied_equalities_for_ecs(root,
1078                                                                                                         root->eq_classes,
1079                                                                                                         join_relids,
1080                                                                                                         outer_relids,
1081                                                                                                         inner_rel);
1082 }
1083
1084 /*
1085  * generate_join_implied_equalities_for_ecs
1086  *        As above, but consider only the listed ECs.
1087  */
1088 List *
1089 generate_join_implied_equalities_for_ecs(PlannerInfo *root,
1090                                                                                  List *eclasses,
1091                                                                                  Relids join_relids,
1092                                                                                  Relids outer_relids,
1093                                                                                  RelOptInfo *inner_rel)
1094 {
1095         List       *result = NIL;
1096         Relids          inner_relids = inner_rel->relids;
1097         Relids          nominal_inner_relids;
1098         Relids          nominal_join_relids;
1099         ListCell   *lc;
1100
1101         /* If inner rel is a child, extra setup work is needed */
1102         if (IS_OTHER_REL(inner_rel))
1103         {
1104                 Assert(!bms_is_empty(inner_rel->top_parent_relids));
1105
1106                 /* Fetch relid set for the topmost parent rel */
1107                 nominal_inner_relids = inner_rel->top_parent_relids;
1108                 /* ECs will be marked with the parent's relid, not the child's */
1109                 nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
1110         }
1111         else
1112         {
1113                 nominal_inner_relids = inner_relids;
1114                 nominal_join_relids = join_relids;
1115         }
1116
1117         foreach(lc, eclasses)
1118         {
1119                 EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
1120                 List       *sublist = NIL;
1121
1122                 /* ECs containing consts do not need any further enforcement */
1123                 if (ec->ec_has_const)
1124                         continue;
1125
1126                 /* Single-member ECs won't generate any deductions */
1127                 if (list_length(ec->ec_members) <= 1)
1128                         continue;
1129
1130                 /* We can quickly ignore any that don't overlap the join, too */
1131                 if (!bms_overlap(ec->ec_relids, nominal_join_relids))
1132                         continue;
1133
1134                 if (!ec->ec_broken)
1135                         sublist = generate_join_implied_equalities_normal(root,
1136                                                                                                                           ec,
1137                                                                                                                           join_relids,
1138                                                                                                                           outer_relids,
1139                                                                                                                           inner_relids);
1140
1141                 /* Recover if we failed to generate required derived clauses */
1142                 if (ec->ec_broken)
1143                         sublist = generate_join_implied_equalities_broken(root,
1144                                                                                                                           ec,
1145                                                                                                                           nominal_join_relids,
1146                                                                                                                           outer_relids,
1147                                                                                                                           nominal_inner_relids,
1148                                                                                                                           inner_rel);
1149
1150                 result = list_concat(result, sublist);
1151         }
1152
1153         return result;
1154 }
1155
1156 /*
1157  * generate_join_implied_equalities for a still-valid EC
1158  */
1159 static List *
1160 generate_join_implied_equalities_normal(PlannerInfo *root,
1161                                                                                 EquivalenceClass *ec,
1162                                                                                 Relids join_relids,
1163                                                                                 Relids outer_relids,
1164                                                                                 Relids inner_relids)
1165 {
1166         List       *result = NIL;
1167         List       *new_members = NIL;
1168         List       *outer_members = NIL;
1169         List       *inner_members = NIL;
1170         ListCell   *lc1;
1171
1172         /*
1173          * First, scan the EC to identify member values that are computable at the
1174          * outer rel, at the inner rel, or at this relation but not in either
1175          * input rel.  The outer-rel members should already be enforced equal,
1176          * likewise for the inner-rel members.  We'll need to create clauses to
1177          * enforce that any newly computable members are all equal to each other
1178          * as well as to at least one input member, plus enforce at least one
1179          * outer-rel member equal to at least one inner-rel member.
1180          */
1181         foreach(lc1, ec->ec_members)
1182         {
1183                 EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
1184
1185                 /*
1186                  * We don't need to check explicitly for child EC members.  This test
1187                  * against join_relids will cause them to be ignored except when
1188                  * considering a child inner rel, which is what we want.
1189                  */
1190                 if (!bms_is_subset(cur_em->em_relids, join_relids))
1191                         continue;                       /* not computable yet, or wrong child */
1192
1193                 if (bms_is_subset(cur_em->em_relids, outer_relids))
1194                         outer_members = lappend(outer_members, cur_em);
1195                 else if (bms_is_subset(cur_em->em_relids, inner_relids))
1196                         inner_members = lappend(inner_members, cur_em);
1197                 else
1198                         new_members = lappend(new_members, cur_em);
1199         }
1200
1201         /*
1202          * First, select the joinclause if needed.  We can equate any one outer
1203          * member to any one inner member, but we have to find a datatype
1204          * combination for which an opfamily member operator exists.  If we have
1205          * choices, we prefer simple Var members (possibly with RelabelType) since
1206          * these are (a) cheapest to compute at runtime and (b) most likely to
1207          * have useful statistics. Also, prefer operators that are also
1208          * hashjoinable.
1209          */
1210         if (outer_members && inner_members)
1211         {
1212                 EquivalenceMember *best_outer_em = NULL;
1213                 EquivalenceMember *best_inner_em = NULL;
1214                 Oid                     best_eq_op = InvalidOid;
1215                 int                     best_score = -1;
1216                 RestrictInfo *rinfo;
1217
1218                 foreach(lc1, outer_members)
1219                 {
1220                         EquivalenceMember *outer_em = (EquivalenceMember *) lfirst(lc1);
1221                         ListCell   *lc2;
1222
1223                         foreach(lc2, inner_members)
1224                         {
1225                                 EquivalenceMember *inner_em = (EquivalenceMember *) lfirst(lc2);
1226                                 Oid                     eq_op;
1227                                 int                     score;
1228
1229                                 eq_op = select_equality_operator(ec,
1230                                                                                                  outer_em->em_datatype,
1231                                                                                                  inner_em->em_datatype);
1232                                 if (!OidIsValid(eq_op))
1233                                         continue;
1234                                 score = 0;
1235                                 if (IsA(outer_em->em_expr, Var) ||
1236                                         (IsA(outer_em->em_expr, RelabelType) &&
1237                                          IsA(((RelabelType *) outer_em->em_expr)->arg, Var)))
1238                                         score++;
1239                                 if (IsA(inner_em->em_expr, Var) ||
1240                                         (IsA(inner_em->em_expr, RelabelType) &&
1241                                          IsA(((RelabelType *) inner_em->em_expr)->arg, Var)))
1242                                         score++;
1243                                 if (op_hashjoinable(eq_op,
1244                                                                         exprType((Node *) outer_em->em_expr)))
1245                                         score++;
1246                                 if (score > best_score)
1247                                 {
1248                                         best_outer_em = outer_em;
1249                                         best_inner_em = inner_em;
1250                                         best_eq_op = eq_op;
1251                                         best_score = score;
1252                                         if (best_score == 3)
1253                                                 break;  /* no need to look further */
1254                                 }
1255                         }
1256                         if (best_score == 3)
1257                                 break;                  /* no need to look further */
1258                 }
1259                 if (best_score < 0)
1260                 {
1261                         /* failed... */
1262                         ec->ec_broken = true;
1263                         return NIL;
1264                 }
1265
1266                 /*
1267                  * Create clause, setting parent_ec to mark it as redundant with other
1268                  * joinclauses
1269                  */
1270                 rinfo = create_join_clause(root, ec, best_eq_op,
1271                                                                    best_outer_em, best_inner_em,
1272                                                                    ec);
1273
1274                 result = lappend(result, rinfo);
1275         }
1276
1277         /*
1278          * Now deal with building restrictions for any expressions that involve
1279          * Vars from both sides of the join.  We have to equate all of these to
1280          * each other as well as to at least one old member (if any).
1281          *
1282          * XXX as in generate_base_implied_equalities_no_const, we could be a lot
1283          * smarter here to avoid unnecessary failures in cross-type situations.
1284          * For now, use the same left-to-right method used there.
1285          */
1286         if (new_members)
1287         {
1288                 List       *old_members = list_concat(outer_members, inner_members);
1289                 EquivalenceMember *prev_em = NULL;
1290                 RestrictInfo *rinfo;
1291
1292                 /* For now, arbitrarily take the first old_member as the one to use */
1293                 if (old_members)
1294                         new_members = lappend(new_members, linitial(old_members));
1295
1296                 foreach(lc1, new_members)
1297                 {
1298                         EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
1299
1300                         if (prev_em != NULL)
1301                         {
1302                                 Oid                     eq_op;
1303
1304                                 eq_op = select_equality_operator(ec,
1305                                                                                                  prev_em->em_datatype,
1306                                                                                                  cur_em->em_datatype);
1307                                 if (!OidIsValid(eq_op))
1308                                 {
1309                                         /* failed... */
1310                                         ec->ec_broken = true;
1311                                         return NIL;
1312                                 }
1313                                 /* do NOT set parent_ec, this qual is not redundant! */
1314                                 rinfo = create_join_clause(root, ec, eq_op,
1315                                                                                    prev_em, cur_em,
1316                                                                                    NULL);
1317
1318                                 result = lappend(result, rinfo);
1319                         }
1320                         prev_em = cur_em;
1321                 }
1322         }
1323
1324         return result;
1325 }
1326
1327 /*
1328  * generate_join_implied_equalities cleanup after failure
1329  *
1330  * Return any original RestrictInfos that are enforceable at this join.
1331  *
1332  * In the case of a child inner relation, we have to translate the
1333  * original RestrictInfos from parent to child Vars.
1334  */
1335 static List *
1336 generate_join_implied_equalities_broken(PlannerInfo *root,
1337                                                                                 EquivalenceClass *ec,
1338                                                                                 Relids nominal_join_relids,
1339                                                                                 Relids outer_relids,
1340                                                                                 Relids nominal_inner_relids,
1341                                                                                 RelOptInfo *inner_rel)
1342 {
1343         List       *result = NIL;
1344         ListCell   *lc;
1345
1346         foreach(lc, ec->ec_sources)
1347         {
1348                 RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
1349                 Relids          clause_relids = restrictinfo->required_relids;
1350
1351                 if (bms_is_subset(clause_relids, nominal_join_relids) &&
1352                         !bms_is_subset(clause_relids, outer_relids) &&
1353                         !bms_is_subset(clause_relids, nominal_inner_relids))
1354                         result = lappend(result, restrictinfo);
1355         }
1356
1357         /*
1358          * If we have to translate, just brute-force apply adjust_appendrel_attrs
1359          * to all the RestrictInfos at once.  This will result in returning
1360          * RestrictInfos that are not listed in ec_derives, but there shouldn't be
1361          * any duplication, and it's a sufficiently narrow corner case that we
1362          * shouldn't sweat too much over it anyway.
1363          *
1364          * Since inner_rel might be an indirect descendant of the baserel
1365          * mentioned in the ec_sources clauses, we have to be prepared to apply
1366          * multiple levels of Var translation.
1367          */
1368         if (IS_OTHER_REL(inner_rel) && result != NIL)
1369                 result = (List *) adjust_appendrel_attrs_multilevel(root,
1370                                                                                                                         (Node *) result,
1371                                                                                                                         inner_rel->relids,
1372                                                                                                                         inner_rel->top_parent_relids);
1373
1374         return result;
1375 }
1376
1377
1378 /*
1379  * select_equality_operator
1380  *        Select a suitable equality operator for comparing two EC members
1381  *
1382  * Returns InvalidOid if no operator can be found for this datatype combination
1383  */
1384 static Oid
1385 select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype)
1386 {
1387         ListCell   *lc;
1388
1389         foreach(lc, ec->ec_opfamilies)
1390         {
1391                 Oid                     opfamily = lfirst_oid(lc);
1392                 Oid                     opno;
1393
1394                 opno = get_opfamily_member(opfamily, lefttype, righttype,
1395                                                                    BTEqualStrategyNumber);
1396                 if (!OidIsValid(opno))
1397                         continue;
1398                 /* If no barrier quals in query, don't worry about leaky operators */
1399                 if (ec->ec_max_security == 0)
1400                         return opno;
1401                 /* Otherwise, insist that selected operators be leakproof */
1402                 if (get_func_leakproof(get_opcode(opno)))
1403                         return opno;
1404         }
1405         return InvalidOid;
1406 }
1407
1408
1409 /*
1410  * create_join_clause
1411  *        Find or make a RestrictInfo comparing the two given EC members
1412  *        with the given operator.
1413  *
1414  * parent_ec is either equal to ec (if the clause is a potentially-redundant
1415  * join clause) or NULL (if not).  We have to treat this as part of the
1416  * match requirements --- it's possible that a clause comparing the same two
1417  * EMs is a join clause in one join path and a restriction clause in another.
1418  */
1419 static RestrictInfo *
1420 create_join_clause(PlannerInfo *root,
1421                                    EquivalenceClass *ec, Oid opno,
1422                                    EquivalenceMember *leftem,
1423                                    EquivalenceMember *rightem,
1424                                    EquivalenceClass *parent_ec)
1425 {
1426         RestrictInfo *rinfo;
1427         ListCell   *lc;
1428         MemoryContext oldcontext;
1429
1430         /*
1431          * Search to see if we already built a RestrictInfo for this pair of
1432          * EquivalenceMembers.  We can use either original source clauses or
1433          * previously-derived clauses.  The check on opno is probably redundant,
1434          * but be safe ...
1435          */
1436         foreach(lc, ec->ec_sources)
1437         {
1438                 rinfo = (RestrictInfo *) lfirst(lc);
1439                 if (rinfo->left_em == leftem &&
1440                         rinfo->right_em == rightem &&
1441                         rinfo->parent_ec == parent_ec &&
1442                         opno == ((OpExpr *) rinfo->clause)->opno)
1443                         return rinfo;
1444         }
1445
1446         foreach(lc, ec->ec_derives)
1447         {
1448                 rinfo = (RestrictInfo *) lfirst(lc);
1449                 if (rinfo->left_em == leftem &&
1450                         rinfo->right_em == rightem &&
1451                         rinfo->parent_ec == parent_ec &&
1452                         opno == ((OpExpr *) rinfo->clause)->opno)
1453                         return rinfo;
1454         }
1455
1456         /*
1457          * Not there, so build it, in planner context so we can re-use it. (Not
1458          * important in normal planning, but definitely so in GEQO.)
1459          */
1460         oldcontext = MemoryContextSwitchTo(root->planner_cxt);
1461
1462         rinfo = build_implied_join_equality(opno,
1463                                                                                 ec->ec_collation,
1464                                                                                 leftem->em_expr,
1465                                                                                 rightem->em_expr,
1466                                                                                 bms_union(leftem->em_relids,
1467                                                                                                   rightem->em_relids),
1468                                                                                 bms_union(leftem->em_nullable_relids,
1469                                                                                                   rightem->em_nullable_relids),
1470                                                                                 ec->ec_min_security);
1471
1472         /* Mark the clause as redundant, or not */
1473         rinfo->parent_ec = parent_ec;
1474
1475         /*
1476          * We know the correct values for left_ec/right_ec, ie this particular EC,
1477          * so we can just set them directly instead of forcing another lookup.
1478          */
1479         rinfo->left_ec = ec;
1480         rinfo->right_ec = ec;
1481
1482         /* Mark it as usable with these EMs */
1483         rinfo->left_em = leftem;
1484         rinfo->right_em = rightem;
1485         /* and save it for possible re-use */
1486         ec->ec_derives = lappend(ec->ec_derives, rinfo);
1487
1488         MemoryContextSwitchTo(oldcontext);
1489
1490         return rinfo;
1491 }
1492
1493
1494 /*
1495  * reconsider_outer_join_clauses
1496  *        Re-examine any outer-join clauses that were set aside by
1497  *        distribute_qual_to_rels(), and see if we can derive any
1498  *        EquivalenceClasses from them.  Then, if they were not made
1499  *        redundant, push them out into the regular join-clause lists.
1500  *
1501  * When we have mergejoinable clauses A = B that are outer-join clauses,
1502  * we can't blindly combine them with other clauses A = C to deduce B = C,
1503  * since in fact the "equality" A = B won't necessarily hold above the
1504  * outer join (one of the variables might be NULL instead).  Nonetheless
1505  * there are cases where we can add qual clauses using transitivity.
1506  *
1507  * One case that we look for here is an outer-join clause OUTERVAR = INNERVAR
1508  * for which there is also an equivalence clause OUTERVAR = CONSTANT.
1509  * It is safe and useful to push a clause INNERVAR = CONSTANT into the
1510  * evaluation of the inner (nullable) relation, because any inner rows not
1511  * meeting this condition will not contribute to the outer-join result anyway.
1512  * (Any outer rows they could join to will be eliminated by the pushed-down
1513  * equivalence clause.)
1514  *
1515  * Note that the above rule does not work for full outer joins; nor is it
1516  * very interesting to consider cases where the generated equivalence clause
1517  * would involve relations outside the outer join, since such clauses couldn't
1518  * be pushed into the inner side's scan anyway.  So the restriction to
1519  * outervar = pseudoconstant is not really giving up anything.
1520  *
1521  * For full-join cases, we can only do something useful if it's a FULL JOIN
1522  * USING and a merged column has an equivalence MERGEDVAR = CONSTANT.
1523  * By the time it gets here, the merged column will look like
1524  *              COALESCE(LEFTVAR, RIGHTVAR)
1525  * and we will have a full-join clause LEFTVAR = RIGHTVAR that we can match
1526  * the COALESCE expression to. In this situation we can push LEFTVAR = CONSTANT
1527  * and RIGHTVAR = CONSTANT into the input relations, since any rows not
1528  * meeting these conditions cannot contribute to the join result.
1529  *
1530  * Again, there isn't any traction to be gained by trying to deal with
1531  * clauses comparing a mergedvar to a non-pseudoconstant.  So we can make
1532  * use of the EquivalenceClasses to search for matching variables that were
1533  * equivalenced to constants.  The interesting outer-join clauses were
1534  * accumulated for us by distribute_qual_to_rels.
1535  *
1536  * When we find one of these cases, we implement the changes we want by
1537  * generating a new equivalence clause INNERVAR = CONSTANT (or LEFTVAR, etc)
1538  * and pushing it into the EquivalenceClass structures.  This is because we
1539  * may already know that INNERVAR is equivalenced to some other var(s), and
1540  * we'd like the constant to propagate to them too.  Note that it would be
1541  * unsafe to merge any existing EC for INNERVAR with the OUTERVAR's EC ---
1542  * that could result in propagating constant restrictions from
1543  * INNERVAR to OUTERVAR, which would be very wrong.
1544  *
1545  * It's possible that the INNERVAR is also an OUTERVAR for some other
1546  * outer-join clause, in which case the process can be repeated.  So we repeat
1547  * looping over the lists of clauses until no further deductions can be made.
1548  * Whenever we do make a deduction, we remove the generating clause from the
1549  * lists, since we don't want to make the same deduction twice.
1550  *
1551  * If we don't find any match for a set-aside outer join clause, we must
1552  * throw it back into the regular joinclause processing by passing it to
1553  * distribute_restrictinfo_to_rels().  If we do generate a derived clause,
1554  * however, the outer-join clause is redundant.  We still throw it back,
1555  * because otherwise the join will be seen as a clauseless join and avoided
1556  * during join order searching; but we mark it as redundant to keep from
1557  * messing up the joinrel's size estimate.  (This behavior means that the
1558  * API for this routine is uselessly complex: we could have just put all
1559  * the clauses into the regular processing initially.  We keep it because
1560  * someday we might want to do something else, such as inserting "dummy"
1561  * joinclauses instead of real ones.)
1562  *
1563  * Outer join clauses that are marked outerjoin_delayed are special: this
1564  * condition means that one or both VARs might go to null due to a lower
1565  * outer join.  We can still push a constant through the clause, but only
1566  * if its operator is strict; and we *have to* throw the clause back into
1567  * regular joinclause processing.  By keeping the strict join clause,
1568  * we ensure that any null-extended rows that are mistakenly generated due
1569  * to suppressing rows not matching the constant will be rejected at the
1570  * upper outer join.  (This doesn't work for full-join clauses.)
1571  */
1572 void
1573 reconsider_outer_join_clauses(PlannerInfo *root)
1574 {
1575         bool            found;
1576         ListCell   *cell;
1577         ListCell   *prev;
1578         ListCell   *next;
1579
1580         /* Outer loop repeats until we find no more deductions */
1581         do
1582         {
1583                 found = false;
1584
1585                 /* Process the LEFT JOIN clauses */
1586                 prev = NULL;
1587                 for (cell = list_head(root->left_join_clauses); cell; cell = next)
1588                 {
1589                         RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
1590
1591                         next = lnext(cell);
1592                         if (reconsider_outer_join_clause(root, rinfo, true))
1593                         {
1594                                 found = true;
1595                                 /* remove it from the list */
1596                                 root->left_join_clauses =
1597                                         list_delete_cell(root->left_join_clauses, cell, prev);
1598                                 /* we throw it back anyway (see notes above) */
1599                                 /* but the thrown-back clause has no extra selectivity */
1600                                 rinfo->norm_selec = 2.0;
1601                                 rinfo->outer_selec = 1.0;
1602                                 distribute_restrictinfo_to_rels(root, rinfo);
1603                         }
1604                         else
1605                                 prev = cell;
1606                 }
1607
1608                 /* Process the RIGHT JOIN clauses */
1609                 prev = NULL;
1610                 for (cell = list_head(root->right_join_clauses); cell; cell = next)
1611                 {
1612                         RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
1613
1614                         next = lnext(cell);
1615                         if (reconsider_outer_join_clause(root, rinfo, false))
1616                         {
1617                                 found = true;
1618                                 /* remove it from the list */
1619                                 root->right_join_clauses =
1620                                         list_delete_cell(root->right_join_clauses, cell, prev);
1621                                 /* we throw it back anyway (see notes above) */
1622                                 /* but the thrown-back clause has no extra selectivity */
1623                                 rinfo->norm_selec = 2.0;
1624                                 rinfo->outer_selec = 1.0;
1625                                 distribute_restrictinfo_to_rels(root, rinfo);
1626                         }
1627                         else
1628                                 prev = cell;
1629                 }
1630
1631                 /* Process the FULL JOIN clauses */
1632                 prev = NULL;
1633                 for (cell = list_head(root->full_join_clauses); cell; cell = next)
1634                 {
1635                         RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
1636
1637                         next = lnext(cell);
1638                         if (reconsider_full_join_clause(root, rinfo))
1639                         {
1640                                 found = true;
1641                                 /* remove it from the list */
1642                                 root->full_join_clauses =
1643                                         list_delete_cell(root->full_join_clauses, cell, prev);
1644                                 /* we throw it back anyway (see notes above) */
1645                                 /* but the thrown-back clause has no extra selectivity */
1646                                 rinfo->norm_selec = 2.0;
1647                                 rinfo->outer_selec = 1.0;
1648                                 distribute_restrictinfo_to_rels(root, rinfo);
1649                         }
1650                         else
1651                                 prev = cell;
1652                 }
1653         } while (found);
1654
1655         /* Now, any remaining clauses have to be thrown back */
1656         foreach(cell, root->left_join_clauses)
1657         {
1658                 RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
1659
1660                 distribute_restrictinfo_to_rels(root, rinfo);
1661         }
1662         foreach(cell, root->right_join_clauses)
1663         {
1664                 RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
1665
1666                 distribute_restrictinfo_to_rels(root, rinfo);
1667         }
1668         foreach(cell, root->full_join_clauses)
1669         {
1670                 RestrictInfo *rinfo = (RestrictInfo *) lfirst(cell);
1671
1672                 distribute_restrictinfo_to_rels(root, rinfo);
1673         }
1674 }
1675
1676 /*
1677  * reconsider_outer_join_clauses for a single LEFT/RIGHT JOIN clause
1678  *
1679  * Returns true if we were able to propagate a constant through the clause.
1680  */
1681 static bool
1682 reconsider_outer_join_clause(PlannerInfo *root, RestrictInfo *rinfo,
1683                                                          bool outer_on_left)
1684 {
1685         Expr       *outervar,
1686                            *innervar;
1687         Oid                     opno,
1688                                 collation,
1689                                 left_type,
1690                                 right_type,
1691                                 inner_datatype;
1692         Relids          inner_relids,
1693                                 inner_nullable_relids;
1694         ListCell   *lc1;
1695
1696         Assert(is_opclause(rinfo->clause));
1697         opno = ((OpExpr *) rinfo->clause)->opno;
1698         collation = ((OpExpr *) rinfo->clause)->inputcollid;
1699
1700         /* If clause is outerjoin_delayed, operator must be strict */
1701         if (rinfo->outerjoin_delayed && !op_strict(opno))
1702                 return false;
1703
1704         /* Extract needed info from the clause */
1705         op_input_types(opno, &left_type, &right_type);
1706         if (outer_on_left)
1707         {
1708                 outervar = (Expr *) get_leftop(rinfo->clause);
1709                 innervar = (Expr *) get_rightop(rinfo->clause);
1710                 inner_datatype = right_type;
1711                 inner_relids = rinfo->right_relids;
1712         }
1713         else
1714         {
1715                 outervar = (Expr *) get_rightop(rinfo->clause);
1716                 innervar = (Expr *) get_leftop(rinfo->clause);
1717                 inner_datatype = left_type;
1718                 inner_relids = rinfo->left_relids;
1719         }
1720         inner_nullable_relids = bms_intersect(inner_relids,
1721                                                                                   rinfo->nullable_relids);
1722
1723         /* Scan EquivalenceClasses for a match to outervar */
1724         foreach(lc1, root->eq_classes)
1725         {
1726                 EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
1727                 bool            match;
1728                 ListCell   *lc2;
1729
1730                 /* Ignore EC unless it contains pseudoconstants */
1731                 if (!cur_ec->ec_has_const)
1732                         continue;
1733                 /* Never match to a volatile EC */
1734                 if (cur_ec->ec_has_volatile)
1735                         continue;
1736                 /* It has to match the outer-join clause as to semantics, too */
1737                 if (collation != cur_ec->ec_collation)
1738                         continue;
1739                 if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
1740                         continue;
1741                 /* Does it contain a match to outervar? */
1742                 match = false;
1743                 foreach(lc2, cur_ec->ec_members)
1744                 {
1745                         EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
1746
1747                         Assert(!cur_em->em_is_child);   /* no children yet */
1748                         if (equal(outervar, cur_em->em_expr))
1749                         {
1750                                 match = true;
1751                                 break;
1752                         }
1753                 }
1754                 if (!match)
1755                         continue;                       /* no match, so ignore this EC */
1756
1757                 /*
1758                  * Yes it does!  Try to generate a clause INNERVAR = CONSTANT for each
1759                  * CONSTANT in the EC.  Note that we must succeed with at least one
1760                  * constant before we can decide to throw away the outer-join clause.
1761                  */
1762                 match = false;
1763                 foreach(lc2, cur_ec->ec_members)
1764                 {
1765                         EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
1766                         Oid                     eq_op;
1767                         RestrictInfo *newrinfo;
1768
1769                         if (!cur_em->em_is_const)
1770                                 continue;               /* ignore non-const members */
1771                         eq_op = select_equality_operator(cur_ec,
1772                                                                                          inner_datatype,
1773                                                                                          cur_em->em_datatype);
1774                         if (!OidIsValid(eq_op))
1775                                 continue;               /* can't generate equality */
1776                         newrinfo = build_implied_join_equality(eq_op,
1777                                                                                                    cur_ec->ec_collation,
1778                                                                                                    innervar,
1779                                                                                                    cur_em->em_expr,
1780                                                                                                    bms_copy(inner_relids),
1781                                                                                                    bms_copy(inner_nullable_relids),
1782                                                                                                    cur_ec->ec_min_security);
1783                         if (process_equivalence(root, &newrinfo, true))
1784                                 match = true;
1785                 }
1786
1787                 /*
1788                  * If we were able to equate INNERVAR to any constant, report success.
1789                  * Otherwise, fall out of the search loop, since we know the OUTERVAR
1790                  * appears in at most one EC.
1791                  */
1792                 if (match)
1793                         return true;
1794                 else
1795                         break;
1796         }
1797
1798         return false;                           /* failed to make any deduction */
1799 }
1800
1801 /*
1802  * reconsider_outer_join_clauses for a single FULL JOIN clause
1803  *
1804  * Returns true if we were able to propagate a constant through the clause.
1805  */
1806 static bool
1807 reconsider_full_join_clause(PlannerInfo *root, RestrictInfo *rinfo)
1808 {
1809         Expr       *leftvar;
1810         Expr       *rightvar;
1811         Oid                     opno,
1812                                 collation,
1813                                 left_type,
1814                                 right_type;
1815         Relids          left_relids,
1816                                 right_relids,
1817                                 left_nullable_relids,
1818                                 right_nullable_relids;
1819         ListCell   *lc1;
1820
1821         /* Can't use an outerjoin_delayed clause here */
1822         if (rinfo->outerjoin_delayed)
1823                 return false;
1824
1825         /* Extract needed info from the clause */
1826         Assert(is_opclause(rinfo->clause));
1827         opno = ((OpExpr *) rinfo->clause)->opno;
1828         collation = ((OpExpr *) rinfo->clause)->inputcollid;
1829         op_input_types(opno, &left_type, &right_type);
1830         leftvar = (Expr *) get_leftop(rinfo->clause);
1831         rightvar = (Expr *) get_rightop(rinfo->clause);
1832         left_relids = rinfo->left_relids;
1833         right_relids = rinfo->right_relids;
1834         left_nullable_relids = bms_intersect(left_relids,
1835                                                                                  rinfo->nullable_relids);
1836         right_nullable_relids = bms_intersect(right_relids,
1837                                                                                   rinfo->nullable_relids);
1838
1839         foreach(lc1, root->eq_classes)
1840         {
1841                 EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
1842                 EquivalenceMember *coal_em = NULL;
1843                 bool            match;
1844                 bool            matchleft;
1845                 bool            matchright;
1846                 ListCell   *lc2;
1847
1848                 /* Ignore EC unless it contains pseudoconstants */
1849                 if (!cur_ec->ec_has_const)
1850                         continue;
1851                 /* Never match to a volatile EC */
1852                 if (cur_ec->ec_has_volatile)
1853                         continue;
1854                 /* It has to match the outer-join clause as to semantics, too */
1855                 if (collation != cur_ec->ec_collation)
1856                         continue;
1857                 if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
1858                         continue;
1859
1860                 /*
1861                  * Does it contain a COALESCE(leftvar, rightvar) construct?
1862                  *
1863                  * We can assume the COALESCE() inputs are in the same order as the
1864                  * join clause, since both were automatically generated in the cases
1865                  * we care about.
1866                  *
1867                  * XXX currently this may fail to match in cross-type cases because
1868                  * the COALESCE will contain typecast operations while the join clause
1869                  * may not (if there is a cross-type mergejoin operator available for
1870                  * the two column types). Is it OK to strip implicit coercions from
1871                  * the COALESCE arguments?
1872                  */
1873                 match = false;
1874                 foreach(lc2, cur_ec->ec_members)
1875                 {
1876                         coal_em = (EquivalenceMember *) lfirst(lc2);
1877                         Assert(!coal_em->em_is_child);  /* no children yet */
1878                         if (IsA(coal_em->em_expr, CoalesceExpr))
1879                         {
1880                                 CoalesceExpr *cexpr = (CoalesceExpr *) coal_em->em_expr;
1881                                 Node       *cfirst;
1882                                 Node       *csecond;
1883
1884                                 if (list_length(cexpr->args) != 2)
1885                                         continue;
1886                                 cfirst = (Node *) linitial(cexpr->args);
1887                                 csecond = (Node *) lsecond(cexpr->args);
1888
1889                                 if (equal(leftvar, cfirst) && equal(rightvar, csecond))
1890                                 {
1891                                         match = true;
1892                                         break;
1893                                 }
1894                         }
1895                 }
1896                 if (!match)
1897                         continue;                       /* no match, so ignore this EC */
1898
1899                 /*
1900                  * Yes it does!  Try to generate clauses LEFTVAR = CONSTANT and
1901                  * RIGHTVAR = CONSTANT for each CONSTANT in the EC.  Note that we must
1902                  * succeed with at least one constant for each var before we can
1903                  * decide to throw away the outer-join clause.
1904                  */
1905                 matchleft = matchright = false;
1906                 foreach(lc2, cur_ec->ec_members)
1907                 {
1908                         EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
1909                         Oid                     eq_op;
1910                         RestrictInfo *newrinfo;
1911
1912                         if (!cur_em->em_is_const)
1913                                 continue;               /* ignore non-const members */
1914                         eq_op = select_equality_operator(cur_ec,
1915                                                                                          left_type,
1916                                                                                          cur_em->em_datatype);
1917                         if (OidIsValid(eq_op))
1918                         {
1919                                 newrinfo = build_implied_join_equality(eq_op,
1920                                                                                                            cur_ec->ec_collation,
1921                                                                                                            leftvar,
1922                                                                                                            cur_em->em_expr,
1923                                                                                                            bms_copy(left_relids),
1924                                                                                                            bms_copy(left_nullable_relids),
1925                                                                                                            cur_ec->ec_min_security);
1926                                 if (process_equivalence(root, &newrinfo, true))
1927                                         matchleft = true;
1928                         }
1929                         eq_op = select_equality_operator(cur_ec,
1930                                                                                          right_type,
1931                                                                                          cur_em->em_datatype);
1932                         if (OidIsValid(eq_op))
1933                         {
1934                                 newrinfo = build_implied_join_equality(eq_op,
1935                                                                                                            cur_ec->ec_collation,
1936                                                                                                            rightvar,
1937                                                                                                            cur_em->em_expr,
1938                                                                                                            bms_copy(right_relids),
1939                                                                                                            bms_copy(right_nullable_relids),
1940                                                                                                            cur_ec->ec_min_security);
1941                                 if (process_equivalence(root, &newrinfo, true))
1942                                         matchright = true;
1943                         }
1944                 }
1945
1946                 /*
1947                  * If we were able to equate both vars to constants, we're done, and
1948                  * we can throw away the full-join clause as redundant.  Moreover, we
1949                  * can remove the COALESCE entry from the EC, since the added
1950                  * restrictions ensure it will always have the expected value. (We
1951                  * don't bother trying to update ec_relids or ec_sources.)
1952                  */
1953                 if (matchleft && matchright)
1954                 {
1955                         cur_ec->ec_members = list_delete_ptr(cur_ec->ec_members, coal_em);
1956                         return true;
1957                 }
1958
1959                 /*
1960                  * Otherwise, fall out of the search loop, since we know the COALESCE
1961                  * appears in at most one EC (XXX might stop being true if we allow
1962                  * stripping of coercions above?)
1963                  */
1964                 break;
1965         }
1966
1967         return false;                           /* failed to make any deduction */
1968 }
1969
1970
1971 /*
1972  * exprs_known_equal
1973  *        Detect whether two expressions are known equal due to equivalence
1974  *        relationships.
1975  *
1976  * Actually, this only shows that the expressions are equal according
1977  * to some opfamily's notion of equality --- but we only use it for
1978  * selectivity estimation, so a fuzzy idea of equality is OK.
1979  *
1980  * Note: does not bother to check for "equal(item1, item2)"; caller must
1981  * check that case if it's possible to pass identical items.
1982  */
1983 bool
1984 exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2)
1985 {
1986         ListCell   *lc1;
1987
1988         foreach(lc1, root->eq_classes)
1989         {
1990                 EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
1991                 bool            item1member = false;
1992                 bool            item2member = false;
1993                 ListCell   *lc2;
1994
1995                 /* Never match to a volatile EC */
1996                 if (ec->ec_has_volatile)
1997                         continue;
1998
1999                 foreach(lc2, ec->ec_members)
2000                 {
2001                         EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
2002
2003                         if (em->em_is_child)
2004                                 continue;               /* ignore children here */
2005                         if (equal(item1, em->em_expr))
2006                                 item1member = true;
2007                         else if (equal(item2, em->em_expr))
2008                                 item2member = true;
2009                         /* Exit as soon as equality is proven */
2010                         if (item1member && item2member)
2011                                 return true;
2012                 }
2013         }
2014         return false;
2015 }
2016
2017
2018 /*
2019  * match_eclasses_to_foreign_key_col
2020  *        See whether a foreign key column match is proven by any eclass.
2021  *
2022  * If the referenced and referencing Vars of the fkey's colno'th column are
2023  * known equal due to any eclass, return that eclass; otherwise return NULL.
2024  * (In principle there might be more than one matching eclass if multiple
2025  * collations are involved, but since collation doesn't matter for equality,
2026  * we ignore that fine point here.)  This is much like exprs_known_equal,
2027  * except that we insist on the comparison operator matching the eclass, so
2028  * that the result is definite not approximate.
2029  */
2030 EquivalenceClass *
2031 match_eclasses_to_foreign_key_col(PlannerInfo *root,
2032                                                                   ForeignKeyOptInfo *fkinfo,
2033                                                                   int colno)
2034 {
2035         Index           var1varno = fkinfo->con_relid;
2036         AttrNumber      var1attno = fkinfo->conkey[colno];
2037         Index           var2varno = fkinfo->ref_relid;
2038         AttrNumber      var2attno = fkinfo->confkey[colno];
2039         Oid                     eqop = fkinfo->conpfeqop[colno];
2040         List       *opfamilies = NIL;   /* compute only if needed */
2041         ListCell   *lc1;
2042
2043         foreach(lc1, root->eq_classes)
2044         {
2045                 EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
2046                 bool            item1member = false;
2047                 bool            item2member = false;
2048                 ListCell   *lc2;
2049
2050                 /* Never match to a volatile EC */
2051                 if (ec->ec_has_volatile)
2052                         continue;
2053                 /* Note: it seems okay to match to "broken" eclasses here */
2054
2055                 foreach(lc2, ec->ec_members)
2056                 {
2057                         EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
2058                         Var                *var;
2059
2060                         if (em->em_is_child)
2061                                 continue;               /* ignore children here */
2062
2063                         /* EM must be a Var, possibly with RelabelType */
2064                         var = (Var *) em->em_expr;
2065                         while (var && IsA(var, RelabelType))
2066                                 var = (Var *) ((RelabelType *) var)->arg;
2067                         if (!(var && IsA(var, Var)))
2068                                 continue;
2069
2070                         /* Match? */
2071                         if (var->varno == var1varno && var->varattno == var1attno)
2072                                 item1member = true;
2073                         else if (var->varno == var2varno && var->varattno == var2attno)
2074                                 item2member = true;
2075
2076                         /* Have we found both PK and FK column in this EC? */
2077                         if (item1member && item2member)
2078                         {
2079                                 /*
2080                                  * Succeed if eqop matches EC's opfamilies.  We could test
2081                                  * this before scanning the members, but it's probably cheaper
2082                                  * to test for member matches first.
2083                                  */
2084                                 if (opfamilies == NIL)  /* compute if we didn't already */
2085                                         opfamilies = get_mergejoin_opfamilies(eqop);
2086                                 if (equal(opfamilies, ec->ec_opfamilies))
2087                                         return ec;
2088                                 /* Otherwise, done with this EC, move on to the next */
2089                                 break;
2090                         }
2091                 }
2092         }
2093         return NULL;
2094 }
2095
2096
2097 /*
2098  * add_child_rel_equivalences
2099  *        Search for EC members that reference the parent_rel, and
2100  *        add transformed members referencing the child_rel.
2101  *
2102  * Note that this function won't be called at all unless we have at least some
2103  * reason to believe that the EC members it generates will be useful.
2104  *
2105  * parent_rel and child_rel could be derived from appinfo, but since the
2106  * caller has already computed them, we might as well just pass them in.
2107  */
2108 void
2109 add_child_rel_equivalences(PlannerInfo *root,
2110                                                    AppendRelInfo *appinfo,
2111                                                    RelOptInfo *parent_rel,
2112                                                    RelOptInfo *child_rel)
2113 {
2114         ListCell   *lc1;
2115
2116         foreach(lc1, root->eq_classes)
2117         {
2118                 EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
2119                 ListCell   *lc2;
2120
2121                 /*
2122                  * If this EC contains a volatile expression, then generating child
2123                  * EMs would be downright dangerous, so skip it.  We rely on a
2124                  * volatile EC having only one EM.
2125                  */
2126                 if (cur_ec->ec_has_volatile)
2127                         continue;
2128
2129                 /*
2130                  * No point in searching if parent rel not mentioned in eclass; but we
2131                  * can't tell that for sure if parent rel is itself a child.
2132                  */
2133                 if (parent_rel->reloptkind == RELOPT_BASEREL &&
2134                         !bms_is_subset(parent_rel->relids, cur_ec->ec_relids))
2135                         continue;
2136
2137                 foreach(lc2, cur_ec->ec_members)
2138                 {
2139                         EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
2140
2141                         if (cur_em->em_is_const)
2142                                 continue;               /* ignore consts here */
2143
2144                         /* Does it reference parent_rel? */
2145                         if (bms_overlap(cur_em->em_relids, parent_rel->relids))
2146                         {
2147                                 /* Yes, generate transformed child version */
2148                                 Expr       *child_expr;
2149                                 Relids          new_relids;
2150                                 Relids          new_nullable_relids;
2151
2152                                 child_expr = (Expr *)
2153                                         adjust_appendrel_attrs(root,
2154                                                                                    (Node *) cur_em->em_expr,
2155                                                                                    1, &appinfo);
2156
2157                                 /*
2158                                  * Transform em_relids to match.  Note we do *not* do
2159                                  * pull_varnos(child_expr) here, as for example the
2160                                  * transformation might have substituted a constant, but we
2161                                  * don't want the child member to be marked as constant.
2162                                  */
2163                                 new_relids = bms_difference(cur_em->em_relids,
2164                                                                                         parent_rel->relids);
2165                                 new_relids = bms_add_members(new_relids, child_rel->relids);
2166
2167                                 /*
2168                                  * And likewise for nullable_relids.  Note this code assumes
2169                                  * parent and child relids are singletons.
2170                                  */
2171                                 new_nullable_relids = cur_em->em_nullable_relids;
2172                                 if (bms_overlap(new_nullable_relids, parent_rel->relids))
2173                                 {
2174                                         new_nullable_relids = bms_difference(new_nullable_relids,
2175                                                                                                                  parent_rel->relids);
2176                                         new_nullable_relids = bms_add_members(new_nullable_relids,
2177                                                                                                                   child_rel->relids);
2178                                 }
2179
2180                                 (void) add_eq_member(cur_ec, child_expr,
2181                                                                          new_relids, new_nullable_relids,
2182                                                                          true, cur_em->em_datatype);
2183                         }
2184                 }
2185         }
2186 }
2187
2188
2189 /*
2190  * generate_implied_equalities_for_column
2191  *        Create EC-derived joinclauses usable with a specific column.
2192  *
2193  * This is used by indxpath.c to extract potentially indexable joinclauses
2194  * from ECs, and can be used by foreign data wrappers for similar purposes.
2195  * We assume that only expressions in Vars of a single table are of interest,
2196  * but the caller provides a callback function to identify exactly which
2197  * such expressions it would like to know about.
2198  *
2199  * We assume that any given table/index column could appear in only one EC.
2200  * (This should be true in all but the most pathological cases, and if it
2201  * isn't, we stop on the first match anyway.)  Therefore, what we return
2202  * is a redundant list of clauses equating the table/index column to each of
2203  * the other-relation values it is known to be equal to.  Any one of
2204  * these clauses can be used to create a parameterized path, and there
2205  * is no value in using more than one.  (But it *is* worthwhile to create
2206  * a separate parameterized path for each one, since that leads to different
2207  * join orders.)
2208  *
2209  * The caller can pass a Relids set of rels we aren't interested in joining
2210  * to, so as to save the work of creating useless clauses.
2211  */
2212 List *
2213 generate_implied_equalities_for_column(PlannerInfo *root,
2214                                                                            RelOptInfo *rel,
2215                                                                            ec_matches_callback_type callback,
2216                                                                            void *callback_arg,
2217                                                                            Relids prohibited_rels)
2218 {
2219         List       *result = NIL;
2220         bool            is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
2221         Relids          parent_relids;
2222         ListCell   *lc1;
2223
2224         /* Indexes are available only on base or "other" member relations. */
2225         Assert(IS_SIMPLE_REL(rel));
2226
2227         /* If it's a child rel, we'll need to know what its parent(s) are */
2228         if (is_child_rel)
2229                 parent_relids = find_childrel_parents(root, rel);
2230         else
2231                 parent_relids = NULL;   /* not used, but keep compiler quiet */
2232
2233         foreach(lc1, root->eq_classes)
2234         {
2235                 EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
2236                 EquivalenceMember *cur_em;
2237                 ListCell   *lc2;
2238
2239                 /*
2240                  * Won't generate joinclauses if const or single-member (the latter
2241                  * test covers the volatile case too)
2242                  */
2243                 if (cur_ec->ec_has_const || list_length(cur_ec->ec_members) <= 1)
2244                         continue;
2245
2246                 /*
2247                  * No point in searching if rel not mentioned in eclass (but we can't
2248                  * tell that for a child rel).
2249                  */
2250                 if (!is_child_rel &&
2251                         !bms_is_subset(rel->relids, cur_ec->ec_relids))
2252                         continue;
2253
2254                 /*
2255                  * Scan members, looking for a match to the target column.  Note that
2256                  * child EC members are considered, but only when they belong to the
2257                  * target relation.  (Unlike regular members, the same expression
2258                  * could be a child member of more than one EC.  Therefore, it's
2259                  * potentially order-dependent which EC a child relation's target
2260                  * column gets matched to.  This is annoying but it only happens in
2261                  * corner cases, so for now we live with just reporting the first
2262                  * match.  See also get_eclass_for_sort_expr.)
2263                  */
2264                 cur_em = NULL;
2265                 foreach(lc2, cur_ec->ec_members)
2266                 {
2267                         cur_em = (EquivalenceMember *) lfirst(lc2);
2268                         if (bms_equal(cur_em->em_relids, rel->relids) &&
2269                                 callback(root, rel, cur_ec, cur_em, callback_arg))
2270                                 break;
2271                         cur_em = NULL;
2272                 }
2273
2274                 if (!cur_em)
2275                         continue;
2276
2277                 /*
2278                  * Found our match.  Scan the other EC members and attempt to generate
2279                  * joinclauses.
2280                  */
2281                 foreach(lc2, cur_ec->ec_members)
2282                 {
2283                         EquivalenceMember *other_em = (EquivalenceMember *) lfirst(lc2);
2284                         Oid                     eq_op;
2285                         RestrictInfo *rinfo;
2286
2287                         if (other_em->em_is_child)
2288                                 continue;               /* ignore children here */
2289
2290                         /* Make sure it'll be a join to a different rel */
2291                         if (other_em == cur_em ||
2292                                 bms_overlap(other_em->em_relids, rel->relids))
2293                                 continue;
2294
2295                         /* Forget it if caller doesn't want joins to this rel */
2296                         if (bms_overlap(other_em->em_relids, prohibited_rels))
2297                                 continue;
2298
2299                         /*
2300                          * Also, if this is a child rel, avoid generating a useless join
2301                          * to its parent rel(s).
2302                          */
2303                         if (is_child_rel &&
2304                                 bms_overlap(parent_relids, other_em->em_relids))
2305                                 continue;
2306
2307                         eq_op = select_equality_operator(cur_ec,
2308                                                                                          cur_em->em_datatype,
2309                                                                                          other_em->em_datatype);
2310                         if (!OidIsValid(eq_op))
2311                                 continue;
2312
2313                         /* set parent_ec to mark as redundant with other joinclauses */
2314                         rinfo = create_join_clause(root, cur_ec, eq_op,
2315                                                                            cur_em, other_em,
2316                                                                            cur_ec);
2317
2318                         result = lappend(result, rinfo);
2319                 }
2320
2321                 /*
2322                  * If somehow we failed to create any join clauses, we might as well
2323                  * keep scanning the ECs for another match.  But if we did make any,
2324                  * we're done, because we don't want to return non-redundant clauses.
2325                  */
2326                 if (result)
2327                         break;
2328         }
2329
2330         return result;
2331 }
2332
2333 /*
2334  * have_relevant_eclass_joinclause
2335  *              Detect whether there is an EquivalenceClass that could produce
2336  *              a joinclause involving the two given relations.
2337  *
2338  * This is essentially a very cut-down version of
2339  * generate_join_implied_equalities().  Note it's OK to occasionally say "yes"
2340  * incorrectly.  Hence we don't bother with details like whether the lack of a
2341  * cross-type operator might prevent the clause from actually being generated.
2342  */
2343 bool
2344 have_relevant_eclass_joinclause(PlannerInfo *root,
2345                                                                 RelOptInfo *rel1, RelOptInfo *rel2)
2346 {
2347         ListCell   *lc1;
2348
2349         foreach(lc1, root->eq_classes)
2350         {
2351                 EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
2352
2353                 /*
2354                  * Won't generate joinclauses if single-member (this test covers the
2355                  * volatile case too)
2356                  */
2357                 if (list_length(ec->ec_members) <= 1)
2358                         continue;
2359
2360                 /*
2361                  * We do not need to examine the individual members of the EC, because
2362                  * all that we care about is whether each rel overlaps the relids of
2363                  * at least one member, and a test on ec_relids is sufficient to prove
2364                  * that.  (As with have_relevant_joinclause(), it is not necessary
2365                  * that the EC be able to form a joinclause relating exactly the two
2366                  * given rels, only that it be able to form a joinclause mentioning
2367                  * both, and this will surely be true if both of them overlap
2368                  * ec_relids.)
2369                  *
2370                  * Note we don't test ec_broken; if we did, we'd need a separate code
2371                  * path to look through ec_sources.  Checking the membership anyway is
2372                  * OK as a possibly-overoptimistic heuristic.
2373                  *
2374                  * We don't test ec_has_const either, even though a const eclass won't
2375                  * generate real join clauses.  This is because if we had "WHERE a.x =
2376                  * b.y and a.x = 42", it is worth considering a join between a and b,
2377                  * since the join result is likely to be small even though it'll end
2378                  * up being an unqualified nestloop.
2379                  */
2380                 if (bms_overlap(rel1->relids, ec->ec_relids) &&
2381                         bms_overlap(rel2->relids, ec->ec_relids))
2382                         return true;
2383         }
2384
2385         return false;
2386 }
2387
2388
2389 /*
2390  * has_relevant_eclass_joinclause
2391  *              Detect whether there is an EquivalenceClass that could produce
2392  *              a joinclause involving the given relation and anything else.
2393  *
2394  * This is the same as have_relevant_eclass_joinclause with the other rel
2395  * implicitly defined as "everything else in the query".
2396  */
2397 bool
2398 has_relevant_eclass_joinclause(PlannerInfo *root, RelOptInfo *rel1)
2399 {
2400         ListCell   *lc1;
2401
2402         foreach(lc1, root->eq_classes)
2403         {
2404                 EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
2405
2406                 /*
2407                  * Won't generate joinclauses if single-member (this test covers the
2408                  * volatile case too)
2409                  */
2410                 if (list_length(ec->ec_members) <= 1)
2411                         continue;
2412
2413                 /*
2414                  * Per the comment in have_relevant_eclass_joinclause, it's sufficient
2415                  * to find an EC that mentions both this rel and some other rel.
2416                  */
2417                 if (bms_overlap(rel1->relids, ec->ec_relids) &&
2418                         !bms_is_subset(ec->ec_relids, rel1->relids))
2419                         return true;
2420         }
2421
2422         return false;
2423 }
2424
2425
2426 /*
2427  * eclass_useful_for_merging
2428  *        Detect whether the EC could produce any mergejoinable join clauses
2429  *        against the specified relation.
2430  *
2431  * This is just a heuristic test and doesn't have to be exact; it's better
2432  * to say "yes" incorrectly than "no".  Hence we don't bother with details
2433  * like whether the lack of a cross-type operator might prevent the clause
2434  * from actually being generated.
2435  */
2436 bool
2437 eclass_useful_for_merging(PlannerInfo *root,
2438                                                   EquivalenceClass *eclass,
2439                                                   RelOptInfo *rel)
2440 {
2441         Relids          relids;
2442         ListCell   *lc;
2443
2444         Assert(!eclass->ec_merged);
2445
2446         /*
2447          * Won't generate joinclauses if const or single-member (the latter test
2448          * covers the volatile case too)
2449          */
2450         if (eclass->ec_has_const || list_length(eclass->ec_members) <= 1)
2451                 return false;
2452
2453         /*
2454          * Note we don't test ec_broken; if we did, we'd need a separate code path
2455          * to look through ec_sources.  Checking the members anyway is OK as a
2456          * possibly-overoptimistic heuristic.
2457          */
2458
2459         /* If specified rel is a child, we must consider the topmost parent rel */
2460         if (IS_OTHER_REL(rel))
2461         {
2462                 Assert(!bms_is_empty(rel->top_parent_relids));
2463                 relids = rel->top_parent_relids;
2464         }
2465         else
2466                 relids = rel->relids;
2467
2468         /* If rel already includes all members of eclass, no point in searching */
2469         if (bms_is_subset(eclass->ec_relids, relids))
2470                 return false;
2471
2472         /* To join, we need a member not in the given rel */
2473         foreach(lc, eclass->ec_members)
2474         {
2475                 EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
2476
2477                 if (cur_em->em_is_child)
2478                         continue;                       /* ignore children here */
2479
2480                 if (!bms_overlap(cur_em->em_relids, relids))
2481                         return true;
2482         }
2483
2484         return false;
2485 }
2486
2487
2488 /*
2489  * is_redundant_derived_clause
2490  *              Test whether rinfo is derived from same EC as any clause in clauselist;
2491  *              if so, it can be presumed to represent a condition that's redundant
2492  *              with that member of the list.
2493  */
2494 bool
2495 is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist)
2496 {
2497         EquivalenceClass *parent_ec = rinfo->parent_ec;
2498         ListCell   *lc;
2499
2500         /* Fail if it's not a potentially-redundant clause from some EC */
2501         if (parent_ec == NULL)
2502                 return false;
2503
2504         foreach(lc, clauselist)
2505         {
2506                 RestrictInfo *otherrinfo = (RestrictInfo *) lfirst(lc);
2507
2508                 if (otherrinfo->parent_ec == parent_ec)
2509                         return true;
2510         }
2511
2512         return false;
2513 }