LCOV - code coverage report
Current view: top level - src/backend/optimizer/path - pathkeys.c (source / functions) Hit Total Coverage
Test: PostgreSQL 14devel Lines: 446 474 94.1 %
Date: 2020-11-27 12:05:55 Functions: 30 30 100.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * pathkeys.c
       4             :  *    Utilities for matching and building path keys
       5             :  *
       6             :  * See src/backend/optimizer/README for a great deal of information about
       7             :  * the nature and use of path keys.
       8             :  *
       9             :  *
      10             :  * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
      11             :  * Portions Copyright (c) 1994, Regents of the University of California
      12             :  *
      13             :  * IDENTIFICATION
      14             :  *    src/backend/optimizer/path/pathkeys.c
      15             :  *
      16             :  *-------------------------------------------------------------------------
      17             :  */
      18             : #include "postgres.h"
      19             : 
      20             : #include "access/stratnum.h"
      21             : #include "catalog/pg_opfamily.h"
      22             : #include "nodes/makefuncs.h"
      23             : #include "nodes/nodeFuncs.h"
      24             : #include "nodes/plannodes.h"
      25             : #include "optimizer/optimizer.h"
      26             : #include "optimizer/pathnode.h"
      27             : #include "optimizer/paths.h"
      28             : #include "partitioning/partbounds.h"
      29             : #include "utils/lsyscache.h"
      30             : 
      31             : 
      32             : static bool pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys);
      33             : static bool matches_boolean_partition_clause(RestrictInfo *rinfo,
      34             :                                              RelOptInfo *partrel,
      35             :                                              int partkeycol);
      36             : static Var *find_var_for_subquery_tle(RelOptInfo *rel, TargetEntry *tle);
      37             : static bool right_merge_direction(PlannerInfo *root, PathKey *pathkey);
      38             : 
      39             : 
      40             : /****************************************************************************
      41             :  *      PATHKEY CONSTRUCTION AND REDUNDANCY TESTING
      42             :  ****************************************************************************/
      43             : 
      44             : /*
      45             :  * make_canonical_pathkey
      46             :  *    Given the parameters for a PathKey, find any pre-existing matching
      47             :  *    pathkey in the query's list of "canonical" pathkeys.  Make a new
      48             :  *    entry if there's not one already.
      49             :  *
      50             :  * Note that this function must not be used until after we have completed
      51             :  * merging EquivalenceClasses.
      52             :  */
      53             : PathKey *
      54     1027744 : make_canonical_pathkey(PlannerInfo *root,
      55             :                        EquivalenceClass *eclass, Oid opfamily,
      56             :                        int strategy, bool nulls_first)
      57             : {
      58             :     PathKey    *pk;
      59             :     ListCell   *lc;
      60             :     MemoryContext oldcontext;
      61             : 
      62             :     /* Can't make canonical pathkeys if the set of ECs might still change */
      63     1027744 :     if (!root->ec_merging_done)
      64           0 :         elog(ERROR, "too soon to build canonical pathkeys");
      65             : 
      66             :     /* The passed eclass might be non-canonical, so chase up to the top */
      67     1027744 :     while (eclass->ec_merged)
      68           0 :         eclass = eclass->ec_merged;
      69             : 
      70     4809836 :     foreach(lc, root->canon_pathkeys)
      71             :     {
      72     4496868 :         pk = (PathKey *) lfirst(lc);
      73     4496868 :         if (eclass == pk->pk_eclass &&
      74      976662 :             opfamily == pk->pk_opfamily &&
      75      976662 :             strategy == pk->pk_strategy &&
      76      714836 :             nulls_first == pk->pk_nulls_first)
      77      714776 :             return pk;
      78             :     }
      79             : 
      80             :     /*
      81             :      * Be sure canonical pathkeys are allocated in the main planning context.
      82             :      * Not an issue in normal planning, but it is for GEQO.
      83             :      */
      84      312968 :     oldcontext = MemoryContextSwitchTo(root->planner_cxt);
      85             : 
      86      312968 :     pk = makeNode(PathKey);
      87      312968 :     pk->pk_eclass = eclass;
      88      312968 :     pk->pk_opfamily = opfamily;
      89      312968 :     pk->pk_strategy = strategy;
      90      312968 :     pk->pk_nulls_first = nulls_first;
      91             : 
      92      312968 :     root->canon_pathkeys = lappend(root->canon_pathkeys, pk);
      93             : 
      94      312968 :     MemoryContextSwitchTo(oldcontext);
      95             : 
      96      312968 :     return pk;
      97             : }
      98             : 
      99             : /*
     100             :  * pathkey_is_redundant
     101             :  *     Is a pathkey redundant with one already in the given list?
     102             :  *
     103             :  * We detect two cases:
     104             :  *
     105             :  * 1. If the new pathkey's equivalence class contains a constant, and isn't
     106             :  * below an outer join, then we can disregard it as a sort key.  An example:
     107             :  *          SELECT ... WHERE x = 42 ORDER BY x, y;
     108             :  * We may as well just sort by y.  Note that because of opfamily matching,
     109             :  * this is semantically correct: we know that the equality constraint is one
     110             :  * that actually binds the variable to a single value in the terms of any
     111             :  * ordering operator that might go with the eclass.  This rule not only lets
     112             :  * us simplify (or even skip) explicit sorts, but also allows matching index
     113             :  * sort orders to a query when there are don't-care index columns.
     114             :  *
     115             :  * 2. If the new pathkey's equivalence class is the same as that of any
     116             :  * existing member of the pathkey list, then it is redundant.  Some examples:
     117             :  *          SELECT ... ORDER BY x, x;
     118             :  *          SELECT ... ORDER BY x, x DESC;
     119             :  *          SELECT ... WHERE x = y ORDER BY x, y;
     120             :  * In all these cases the second sort key cannot distinguish values that are
     121             :  * considered equal by the first, and so there's no point in using it.
     122             :  * Note in particular that we need not compare opfamily (all the opfamilies
     123             :  * of the EC have the same notion of equality) nor sort direction.
     124             :  *
     125             :  * Both the given pathkey and the list members must be canonical for this
     126             :  * to work properly, but that's okay since we no longer ever construct any
     127             :  * non-canonical pathkeys.  (Note: the notion of a pathkey *list* being
     128             :  * canonical includes the additional requirement of no redundant entries,
     129             :  * which is exactly what we are checking for here.)
     130             :  *
     131             :  * Because the equivclass.c machinery forms only one copy of any EC per query,
     132             :  * pointer comparison is enough to decide whether canonical ECs are the same.
     133             :  */
     134             : static bool
     135     1066354 : pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys)
     136             : {
     137     1066354 :     EquivalenceClass *new_ec = new_pathkey->pk_eclass;
     138             :     ListCell   *lc;
     139             : 
     140             :     /* Check for EC containing a constant --- unconditionally redundant */
     141     1066354 :     if (EC_MUST_BE_REDUNDANT(new_ec))
     142      143182 :         return true;
     143             : 
     144             :     /* If same EC already used in list, then redundant */
     145     1038294 :     foreach(lc, pathkeys)
     146             :     {
     147      115552 :         PathKey    *old_pathkey = (PathKey *) lfirst(lc);
     148             : 
     149      115552 :         if (new_ec == old_pathkey->pk_eclass)
     150         430 :             return true;
     151             :     }
     152             : 
     153      922742 :     return false;
     154             : }
     155             : 
     156             : /*
     157             :  * make_pathkey_from_sortinfo
     158             :  *    Given an expression and sort-order information, create a PathKey.
     159             :  *    The result is always a "canonical" PathKey, but it might be redundant.
     160             :  *
     161             :  * expr is the expression, and nullable_relids is the set of base relids
     162             :  * that are potentially nullable below it.
     163             :  *
     164             :  * If the PathKey is being generated from a SortGroupClause, sortref should be
     165             :  * the SortGroupClause's SortGroupRef; otherwise zero.
     166             :  *
     167             :  * If rel is not NULL, it identifies a specific relation we're considering
     168             :  * a path for, and indicates that child EC members for that relation can be
     169             :  * considered.  Otherwise child members are ignored.  (See the comments for
     170             :  * get_eclass_for_sort_expr.)
     171             :  *
     172             :  * create_it is true if we should create any missing EquivalenceClass
     173             :  * needed to represent the sort key.  If it's false, we return NULL if the
     174             :  * sort key isn't already present in any EquivalenceClass.
     175             :  */
     176             : static PathKey *
     177      873342 : make_pathkey_from_sortinfo(PlannerInfo *root,
     178             :                            Expr *expr,
     179             :                            Relids nullable_relids,
     180             :                            Oid opfamily,
     181             :                            Oid opcintype,
     182             :                            Oid collation,
     183             :                            bool reverse_sort,
     184             :                            bool nulls_first,
     185             :                            Index sortref,
     186             :                            Relids rel,
     187             :                            bool create_it)
     188             : {
     189             :     int16       strategy;
     190             :     Oid         equality_op;
     191             :     List       *opfamilies;
     192             :     EquivalenceClass *eclass;
     193             : 
     194      873342 :     strategy = reverse_sort ? BTGreaterStrategyNumber : BTLessStrategyNumber;
     195             : 
     196             :     /*
     197             :      * EquivalenceClasses need to contain opfamily lists based on the family
     198             :      * membership of mergejoinable equality operators, which could belong to
     199             :      * more than one opfamily.  So we have to look up the opfamily's equality
     200             :      * operator and get its membership.
     201             :      */
     202      873342 :     equality_op = get_opfamily_member(opfamily,
     203             :                                       opcintype,
     204             :                                       opcintype,
     205             :                                       BTEqualStrategyNumber);
     206      873342 :     if (!OidIsValid(equality_op))   /* shouldn't happen */
     207           0 :         elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
     208             :              BTEqualStrategyNumber, opcintype, opcintype, opfamily);
     209      873342 :     opfamilies = get_mergejoin_opfamilies(equality_op);
     210      873342 :     if (!opfamilies)            /* certainly should find some */
     211           0 :         elog(ERROR, "could not find opfamilies for equality operator %u",
     212             :              equality_op);
     213             : 
     214             :     /* Now find or (optionally) create a matching EquivalenceClass */
     215      873342 :     eclass = get_eclass_for_sort_expr(root, expr, nullable_relids,
     216             :                                       opfamilies, opcintype, collation,
     217             :                                       sortref, rel, create_it);
     218             : 
     219             :     /* Fail if no EC and !create_it */
     220      873342 :     if (!eclass)
     221      291918 :         return NULL;
     222             : 
     223             :     /* And finally we can find or create a PathKey node */
     224      581424 :     return make_canonical_pathkey(root, eclass, opfamily,
     225             :                                   strategy, nulls_first);
     226             : }
     227             : 
     228             : /*
     229             :  * make_pathkey_from_sortop
     230             :  *    Like make_pathkey_from_sortinfo, but work from a sort operator.
     231             :  *
     232             :  * This should eventually go away, but we need to restructure SortGroupClause
     233             :  * first.
     234             :  */
     235             : static PathKey *
     236       57996 : make_pathkey_from_sortop(PlannerInfo *root,
     237             :                          Expr *expr,
     238             :                          Relids nullable_relids,
     239             :                          Oid ordering_op,
     240             :                          bool nulls_first,
     241             :                          Index sortref,
     242             :                          bool create_it)
     243             : {
     244             :     Oid         opfamily,
     245             :                 opcintype,
     246             :                 collation;
     247             :     int16       strategy;
     248             : 
     249             :     /* Find the operator in pg_amop --- failure shouldn't happen */
     250       57996 :     if (!get_ordering_op_properties(ordering_op,
     251             :                                     &opfamily, &opcintype, &strategy))
     252           0 :         elog(ERROR, "operator %u is not a valid ordering operator",
     253             :              ordering_op);
     254             : 
     255             :     /* Because SortGroupClause doesn't carry collation, consult the expr */
     256       57996 :     collation = exprCollation((Node *) expr);
     257             : 
     258       57996 :     return make_pathkey_from_sortinfo(root,
     259             :                                       expr,
     260             :                                       nullable_relids,
     261             :                                       opfamily,
     262             :                                       opcintype,
     263             :                                       collation,
     264             :                                       (strategy == BTGreaterStrategyNumber),
     265             :                                       nulls_first,
     266             :                                       sortref,
     267             :                                       NULL,
     268             :                                       create_it);
     269             : }
     270             : 
     271             : 
     272             : /****************************************************************************
     273             :  *      PATHKEY COMPARISONS
     274             :  ****************************************************************************/
     275             : 
     276             : /*
     277             :  * compare_pathkeys
     278             :  *    Compare two pathkeys to see if they are equivalent, and if not whether
     279             :  *    one is "better" than the other.
     280             :  *
     281             :  *    We assume the pathkeys are canonical, and so they can be checked for
     282             :  *    equality by simple pointer comparison.
     283             :  */
     284             : PathKeysComparison
     285     5252908 : compare_pathkeys(List *keys1, List *keys2)
     286             : {
     287             :     ListCell   *key1,
     288             :                *key2;
     289             : 
     290             :     /*
     291             :      * Fall out quickly if we are passed two identical lists.  This mostly
     292             :      * catches the case where both are NIL, but that's common enough to
     293             :      * warrant the test.
     294             :      */
     295     5252908 :     if (keys1 == keys2)
     296     2008460 :         return PATHKEYS_EQUAL;
     297             : 
     298     4019638 :     forboth(key1, keys1, key2, keys2)
     299             :     {
     300     1115294 :         PathKey    *pathkey1 = (PathKey *) lfirst(key1);
     301     1115294 :         PathKey    *pathkey2 = (PathKey *) lfirst(key2);
     302             : 
     303     1115294 :         if (pathkey1 != pathkey2)
     304      340104 :             return PATHKEYS_DIFFERENT;  /* no need to keep looking */
     305             :     }
     306             : 
     307             :     /*
     308             :      * If we reached the end of only one list, the other is longer and
     309             :      * therefore not a subset.
     310             :      */
     311     2904344 :     if (key1 != NULL)
     312     1903010 :         return PATHKEYS_BETTER1;    /* key1 is longer */
     313     1001334 :     if (key2 != NULL)
     314      293852 :         return PATHKEYS_BETTER2;    /* key2 is longer */
     315      707482 :     return PATHKEYS_EQUAL;
     316             : }
     317             : 
     318             : /*
     319             :  * pathkeys_contained_in
     320             :  *    Common special case of compare_pathkeys: we just want to know
     321             :  *    if keys2 are at least as well sorted as keys1.
     322             :  */
     323             : bool
     324     1905706 : pathkeys_contained_in(List *keys1, List *keys2)
     325             : {
     326     1905706 :     switch (compare_pathkeys(keys1, keys2))
     327             :     {
     328      497968 :         case PATHKEYS_EQUAL:
     329             :         case PATHKEYS_BETTER2:
     330      497968 :             return true;
     331     1407738 :         default:
     332     1407738 :             break;
     333             :     }
     334     1407738 :     return false;
     335             : }
     336             : 
     337             : /*
     338             :  * pathkeys_count_contained_in
     339             :  *    Same as pathkeys_contained_in, but also sets length of longest
     340             :  *    common prefix of keys1 and keys2.
     341             :  */
     342             : bool
     343      555536 : pathkeys_count_contained_in(List *keys1, List *keys2, int *n_common)
     344             : {
     345      555536 :     int         n = 0;
     346             :     ListCell   *key1,
     347             :                *key2;
     348             : 
     349             :     /*
     350             :      * See if we can avoiding looping through both lists. This optimization
     351             :      * gains us several percent in planning time in a worst-case test.
     352             :      */
     353      555536 :     if (keys1 == keys2)
     354             :     {
     355       30018 :         *n_common = list_length(keys1);
     356       30018 :         return true;
     357             :     }
     358      525518 :     else if (keys1 == NIL)
     359             :     {
     360          20 :         *n_common = 0;
     361          20 :         return true;
     362             :     }
     363      525498 :     else if (keys2 == NIL)
     364             :     {
     365       36620 :         *n_common = 0;
     366       36620 :         return false;
     367             :     }
     368             : 
     369             :     /*
     370             :      * If both lists are non-empty, iterate through both to find out how many
     371             :      * items are shared.
     372             :      */
     373      612982 :     forboth(key1, keys1, key2, keys2)
     374             :     {
     375      491958 :         PathKey    *pathkey1 = (PathKey *) lfirst(key1);
     376      491958 :         PathKey    *pathkey2 = (PathKey *) lfirst(key2);
     377             : 
     378      491958 :         if (pathkey1 != pathkey2)
     379             :         {
     380      367854 :             *n_common = n;
     381      367854 :             return false;
     382             :         }
     383      124104 :         n++;
     384             :     }
     385             : 
     386             :     /* If we ended with a null value, then we've processed the whole list. */
     387      121024 :     *n_common = n;
     388      121024 :     return (key1 == NULL);
     389             : }
     390             : 
     391             : /*
     392             :  * get_cheapest_path_for_pathkeys
     393             :  *    Find the cheapest path (according to the specified criterion) that
     394             :  *    satisfies the given pathkeys and parameterization.
     395             :  *    Return NULL if no such path.
     396             :  *
     397             :  * 'paths' is a list of possible paths that all generate the same relation
     398             :  * 'pathkeys' represents a required ordering (in canonical form!)
     399             :  * 'required_outer' denotes allowable outer relations for parameterized paths
     400             :  * 'cost_criterion' is STARTUP_COST or TOTAL_COST
     401             :  * 'require_parallel_safe' causes us to consider only parallel-safe paths
     402             :  */
     403             : Path *
     404      413080 : get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
     405             :                                Relids required_outer,
     406             :                                CostSelector cost_criterion,
     407             :                                bool require_parallel_safe)
     408             : {
     409      413080 :     Path       *matched_path = NULL;
     410             :     ListCell   *l;
     411             : 
     412     1448096 :     foreach(l, paths)
     413             :     {
     414     1035016 :         Path       *path = (Path *) lfirst(l);
     415             : 
     416             :         /*
     417             :          * Since cost comparison is a lot cheaper than pathkey comparison, do
     418             :          * that first.  (XXX is that still true?)
     419             :          */
     420     1094668 :         if (matched_path != NULL &&
     421       59652 :             compare_path_costs(matched_path, path, cost_criterion) <= 0)
     422       51936 :             continue;
     423             : 
     424      983080 :         if (require_parallel_safe && !path->parallel_safe)
     425           0 :             continue;
     426             : 
     427     1441454 :         if (pathkeys_contained_in(pathkeys, path->pathkeys) &&
     428      458374 :             bms_is_subset(PATH_REQ_OUTER(path), required_outer))
     429      286638 :             matched_path = path;
     430             :     }
     431      413080 :     return matched_path;
     432             : }
     433             : 
     434             : /*
     435             :  * get_cheapest_fractional_path_for_pathkeys
     436             :  *    Find the cheapest path (for retrieving a specified fraction of all
     437             :  *    the tuples) that satisfies the given pathkeys and parameterization.
     438             :  *    Return NULL if no such path.
     439             :  *
     440             :  * See compare_fractional_path_costs() for the interpretation of the fraction
     441             :  * parameter.
     442             :  *
     443             :  * 'paths' is a list of possible paths that all generate the same relation
     444             :  * 'pathkeys' represents a required ordering (in canonical form!)
     445             :  * 'required_outer' denotes allowable outer relations for parameterized paths
     446             :  * 'fraction' is the fraction of the total tuples expected to be retrieved
     447             :  */
     448             : Path *
     449         810 : get_cheapest_fractional_path_for_pathkeys(List *paths,
     450             :                                           List *pathkeys,
     451             :                                           Relids required_outer,
     452             :                                           double fraction)
     453             : {
     454         810 :     Path       *matched_path = NULL;
     455             :     ListCell   *l;
     456             : 
     457        2030 :     foreach(l, paths)
     458             :     {
     459        1220 :         Path       *path = (Path *) lfirst(l);
     460             : 
     461             :         /*
     462             :          * Since cost comparison is a lot cheaper than pathkey comparison, do
     463             :          * that first.  (XXX is that still true?)
     464             :          */
     465        1360 :         if (matched_path != NULL &&
     466         140 :             compare_fractional_path_costs(matched_path, path, fraction) <= 0)
     467          40 :             continue;
     468             : 
     469        1610 :         if (pathkeys_contained_in(pathkeys, path->pathkeys) &&
     470         430 :             bms_is_subset(PATH_REQ_OUTER(path), required_outer))
     471         430 :             matched_path = path;
     472             :     }
     473         810 :     return matched_path;
     474             : }
     475             : 
     476             : 
     477             : /*
     478             :  * get_cheapest_parallel_safe_total_inner
     479             :  *    Find the unparameterized parallel-safe path with the least total cost.
     480             :  */
     481             : Path *
     482       33074 : get_cheapest_parallel_safe_total_inner(List *paths)
     483             : {
     484             :     ListCell   *l;
     485             : 
     486       37118 :     foreach(l, paths)
     487             :     {
     488       36430 :         Path       *innerpath = (Path *) lfirst(l);
     489             : 
     490       71596 :         if (innerpath->parallel_safe &&
     491       35166 :             bms_is_empty(PATH_REQ_OUTER(innerpath)))
     492       32386 :             return innerpath;
     493             :     }
     494             : 
     495         688 :     return NULL;
     496             : }
     497             : 
     498             : /****************************************************************************
     499             :  *      NEW PATHKEY FORMATION
     500             :  ****************************************************************************/
     501             : 
     502             : /*
     503             :  * build_index_pathkeys
     504             :  *    Build a pathkeys list that describes the ordering induced by an index
     505             :  *    scan using the given index.  (Note that an unordered index doesn't
     506             :  *    induce any ordering, so we return NIL.)
     507             :  *
     508             :  * If 'scandir' is BackwardScanDirection, build pathkeys representing a
     509             :  * backwards scan of the index.
     510             :  *
     511             :  * We iterate only key columns of covering indexes, since non-key columns
     512             :  * don't influence index ordering.  The result is canonical, meaning that
     513             :  * redundant pathkeys are removed; it may therefore have fewer entries than
     514             :  * there are key columns in the index.
     515             :  *
     516             :  * Another reason for stopping early is that we may be able to tell that
     517             :  * an index column's sort order is uninteresting for this query.  However,
     518             :  * that test is just based on the existence of an EquivalenceClass and not
     519             :  * on position in pathkey lists, so it's not complete.  Caller should call
     520             :  * truncate_useless_pathkeys() to possibly remove more pathkeys.
     521             :  */
     522             : List *
     523      590304 : build_index_pathkeys(PlannerInfo *root,
     524             :                      IndexOptInfo *index,
     525             :                      ScanDirection scandir)
     526             : {
     527      590304 :     List       *retval = NIL;
     528             :     ListCell   *lc;
     529             :     int         i;
     530             : 
     531      590304 :     if (index->sortopfamily == NULL)
     532           0 :         return NIL;             /* non-orderable index */
     533             : 
     534      590304 :     i = 0;
     535     1093832 :     foreach(lc, index->indextlist)
     536             :     {
     537      782760 :         TargetEntry *indextle = (TargetEntry *) lfirst(lc);
     538             :         Expr       *indexkey;
     539             :         bool        reverse_sort;
     540             :         bool        nulls_first;
     541             :         PathKey    *cpathkey;
     542             : 
     543             :         /*
     544             :          * INCLUDE columns are stored in index unordered, so they don't
     545             :          * support ordered index scan.
     546             :          */
     547      782760 :         if (i >= index->nkeycolumns)
     548           0 :             break;
     549             : 
     550             :         /* We assume we don't need to make a copy of the tlist item */
     551      782760 :         indexkey = indextle->expr;
     552             : 
     553      782760 :         if (ScanDirectionIsBackward(scandir))
     554             :         {
     555      391380 :             reverse_sort = !index->reverse_sort[i];
     556      391380 :             nulls_first = !index->nulls_first[i];
     557             :         }
     558             :         else
     559             :         {
     560      391380 :             reverse_sort = index->reverse_sort[i];
     561      391380 :             nulls_first = index->nulls_first[i];
     562             :         }
     563             : 
     564             :         /*
     565             :          * OK, try to make a canonical pathkey for this sort key.  Note we're
     566             :          * underneath any outer joins, so nullable_relids should be NULL.
     567             :          */
     568     3131040 :         cpathkey = make_pathkey_from_sortinfo(root,
     569             :                                               indexkey,
     570             :                                               NULL,
     571      782760 :                                               index->sortopfamily[i],
     572      782760 :                                               index->opcintype[i],
     573      782760 :                                               index->indexcollations[i],
     574             :                                               reverse_sort,
     575             :                                               nulls_first,
     576             :                                               0,
     577      782760 :                                               index->rel->relids,
     578             :                                               false);
     579             : 
     580      782760 :         if (cpathkey)
     581             :         {
     582             :             /*
     583             :              * We found the sort key in an EquivalenceClass, so it's relevant
     584             :              * for this query.  Add it to list, unless it's redundant.
     585             :              */
     586      503456 :             if (!pathkey_is_redundant(cpathkey, retval))
     587      375440 :                 retval = lappend(retval, cpathkey);
     588             :         }
     589             :         else
     590             :         {
     591             :             /*
     592             :              * Boolean index keys might be redundant even if they do not
     593             :              * appear in an EquivalenceClass, because of our special treatment
     594             :              * of boolean equality conditions --- see the comment for
     595             :              * indexcol_is_bool_constant_for_query().  If that applies, we can
     596             :              * continue to examine lower-order index columns.  Otherwise, the
     597             :              * sort key is not an interesting sort order for this query, so we
     598             :              * should stop considering index columns; any lower-order sort
     599             :              * keys won't be useful either.
     600             :              */
     601      279304 :             if (!indexcol_is_bool_constant_for_query(index, i))
     602      279232 :                 break;
     603             :         }
     604             : 
     605      503528 :         i++;
     606             :     }
     607             : 
     608      590304 :     return retval;
     609             : }
     610             : 
     611             : /*
     612             :  * partkey_is_bool_constant_for_query
     613             :  *
     614             :  * If a partition key column is constrained to have a constant value by the
     615             :  * query's WHERE conditions, then it's irrelevant for sort-order
     616             :  * considerations.  Usually that means we have a restriction clause
     617             :  * WHERE partkeycol = constant, which gets turned into an EquivalenceClass
     618             :  * containing a constant, which is recognized as redundant by
     619             :  * build_partition_pathkeys().  But if the partition key column is a
     620             :  * boolean variable (or expression), then we are not going to see such a
     621             :  * WHERE clause, because expression preprocessing will have simplified it
     622             :  * to "WHERE partkeycol" or "WHERE NOT partkeycol".  So we are not going
     623             :  * to have a matching EquivalenceClass (unless the query also contains
     624             :  * "ORDER BY partkeycol").  To allow such cases to work the same as they would
     625             :  * for non-boolean values, this function is provided to detect whether the
     626             :  * specified partition key column matches a boolean restriction clause.
     627             :  */
     628             : static bool
     629        6532 : partkey_is_bool_constant_for_query(RelOptInfo *partrel, int partkeycol)
     630             : {
     631        6532 :     PartitionScheme partscheme = partrel->part_scheme;
     632             :     ListCell   *lc;
     633             : 
     634             :     /* If the partkey isn't boolean, we can't possibly get a match */
     635        6532 :     if (!IsBooleanOpfamily(partscheme->partopfamily[partkeycol]))
     636        6468 :         return false;
     637             : 
     638             :     /* Check each restriction clause for the partitioned rel */
     639          80 :     foreach(lc, partrel->baserestrictinfo)
     640             :     {
     641          80 :         RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
     642             : 
     643             :         /* Ignore pseudoconstant quals, they won't match */
     644          80 :         if (rinfo->pseudoconstant)
     645           0 :             continue;
     646             : 
     647             :         /* See if we can match the clause's expression to the partkey column */
     648          80 :         if (matches_boolean_partition_clause(rinfo, partrel, partkeycol))
     649          64 :             return true;
     650             :     }
     651             : 
     652           0 :     return false;
     653             : }
     654             : 
     655             : /*
     656             :  * matches_boolean_partition_clause
     657             :  *      Determine if the boolean clause described by rinfo matches
     658             :  *      partrel's partkeycol-th partition key column.
     659             :  *
     660             :  * "Matches" can be either an exact match (equivalent to partkey = true),
     661             :  * or a NOT above an exact match (equivalent to partkey = false).
     662             :  */
     663             : static bool
     664          80 : matches_boolean_partition_clause(RestrictInfo *rinfo,
     665             :                                  RelOptInfo *partrel, int partkeycol)
     666             : {
     667          80 :     Node       *clause = (Node *) rinfo->clause;
     668          80 :     Node       *partexpr = (Node *) linitial(partrel->partexprs[partkeycol]);
     669             : 
     670             :     /* Direct match? */
     671          80 :     if (equal(partexpr, clause))
     672          16 :         return true;
     673             :     /* NOT clause? */
     674          64 :     else if (is_notclause(clause))
     675             :     {
     676          64 :         Node       *arg = (Node *) get_notclausearg((Expr *) clause);
     677             : 
     678          64 :         if (equal(partexpr, arg))
     679          48 :             return true;
     680             :     }
     681             : 
     682          16 :     return false;
     683             : }
     684             : 
     685             : /*
     686             :  * build_partition_pathkeys
     687             :  *    Build a pathkeys list that describes the ordering induced by the
     688             :  *    partitions of partrel, under either forward or backward scan
     689             :  *    as per scandir.
     690             :  *
     691             :  * Caller must have checked that the partitions are properly ordered,
     692             :  * as detected by partitions_are_ordered().
     693             :  *
     694             :  * Sets *partialkeys to true if pathkeys were only built for a prefix of the
     695             :  * partition key, or false if the pathkeys include all columns of the
     696             :  * partition key.
     697             :  */
     698             : List *
     699       25460 : build_partition_pathkeys(PlannerInfo *root, RelOptInfo *partrel,
     700             :                          ScanDirection scandir, bool *partialkeys)
     701             : {
     702       25460 :     List       *retval = NIL;
     703       25460 :     PartitionScheme partscheme = partrel->part_scheme;
     704             :     int         i;
     705             : 
     706             :     Assert(partscheme != NULL);
     707             :     Assert(partitions_are_ordered(partrel->boundinfo, partrel->nparts));
     708             :     /* For now, we can only cope with baserels */
     709             :     Assert(IS_SIMPLE_REL(partrel));
     710             : 
     711       45468 :     for (i = 0; i < partscheme->partnatts; i++)
     712             :     {
     713             :         PathKey    *cpathkey;
     714       26476 :         Expr       *keyCol = (Expr *) linitial(partrel->partexprs[i]);
     715             : 
     716             :         /*
     717             :          * Try to make a canonical pathkey for this partkey.
     718             :          *
     719             :          * We're considering a baserel scan, so nullable_relids should be
     720             :          * NULL.  Also, we assume the PartitionDesc lists any NULL partition
     721             :          * last, so we treat the scan like a NULLS LAST index: we have
     722             :          * nulls_first for backwards scan only.
     723             :          */
     724      105904 :         cpathkey = make_pathkey_from_sortinfo(root,
     725             :                                               keyCol,
     726             :                                               NULL,
     727       26476 :                                               partscheme->partopfamily[i],
     728       26476 :                                               partscheme->partopcintype[i],
     729       26476 :                                               partscheme->partcollation[i],
     730             :                                               ScanDirectionIsBackward(scandir),
     731             :                                               ScanDirectionIsBackward(scandir),
     732             :                                               0,
     733             :                                               partrel->relids,
     734             :                                               false);
     735             : 
     736             : 
     737       26476 :         if (cpathkey)
     738             :         {
     739             :             /*
     740             :              * We found the sort key in an EquivalenceClass, so it's relevant
     741             :              * for this query.  Add it to list, unless it's redundant.
     742             :              */
     743       19944 :             if (!pathkey_is_redundant(cpathkey, retval))
     744        5344 :                 retval = lappend(retval, cpathkey);
     745             :         }
     746             :         else
     747             :         {
     748             :             /*
     749             :              * Boolean partition keys might be redundant even if they do not
     750             :              * appear in an EquivalenceClass, because of our special treatment
     751             :              * of boolean equality conditions --- see the comment for
     752             :              * partkey_is_bool_constant_for_query().  If that applies, we can
     753             :              * continue to examine lower-order partition keys.  Otherwise, the
     754             :              * sort key is not an interesting sort order for this query, so we
     755             :              * should stop considering partition columns; any lower-order sort
     756             :              * keys won't be useful either.
     757             :              */
     758        6532 :             if (!partkey_is_bool_constant_for_query(partrel, i))
     759             :             {
     760        6468 :                 *partialkeys = true;
     761        6468 :                 return retval;
     762             :             }
     763             :         }
     764             :     }
     765             : 
     766       18992 :     *partialkeys = false;
     767       18992 :     return retval;
     768             : }
     769             : 
     770             : /*
     771             :  * build_expression_pathkey
     772             :  *    Build a pathkeys list that describes an ordering by a single expression
     773             :  *    using the given sort operator.
     774             :  *
     775             :  * expr, nullable_relids, and rel are as for make_pathkey_from_sortinfo.
     776             :  * We induce the other arguments assuming default sort order for the operator.
     777             :  *
     778             :  * Similarly to make_pathkey_from_sortinfo, the result is NIL if create_it
     779             :  * is false and the expression isn't already in some EquivalenceClass.
     780             :  */
     781             : List *
     782        6110 : build_expression_pathkey(PlannerInfo *root,
     783             :                          Expr *expr,
     784             :                          Relids nullable_relids,
     785             :                          Oid opno,
     786             :                          Relids rel,
     787             :                          bool create_it)
     788             : {
     789             :     List       *pathkeys;
     790             :     Oid         opfamily,
     791             :                 opcintype;
     792             :     int16       strategy;
     793             :     PathKey    *cpathkey;
     794             : 
     795             :     /* Find the operator in pg_amop --- failure shouldn't happen */
     796        6110 :     if (!get_ordering_op_properties(opno,
     797             :                                     &opfamily, &opcintype, &strategy))
     798           0 :         elog(ERROR, "operator %u is not a valid ordering operator",
     799             :              opno);
     800             : 
     801        6110 :     cpathkey = make_pathkey_from_sortinfo(root,
     802             :                                           expr,
     803             :                                           nullable_relids,
     804             :                                           opfamily,
     805             :                                           opcintype,
     806             :                                           exprCollation((Node *) expr),
     807             :                                           (strategy == BTGreaterStrategyNumber),
     808             :                                           (strategy == BTGreaterStrategyNumber),
     809             :                                           0,
     810             :                                           rel,
     811             :                                           create_it);
     812             : 
     813        6110 :     if (cpathkey)
     814          28 :         pathkeys = list_make1(cpathkey);
     815             :     else
     816        6082 :         pathkeys = NIL;
     817             : 
     818        6110 :     return pathkeys;
     819             : }
     820             : 
     821             : /*
     822             :  * convert_subquery_pathkeys
     823             :  *    Build a pathkeys list that describes the ordering of a subquery's
     824             :  *    result, in the terms of the outer query.  This is essentially a
     825             :  *    task of conversion.
     826             :  *
     827             :  * 'rel': outer query's RelOptInfo for the subquery relation.
     828             :  * 'subquery_pathkeys': the subquery's output pathkeys, in its terms.
     829             :  * 'subquery_tlist': the subquery's output targetlist, in its terms.
     830             :  *
     831             :  * We intentionally don't do truncate_useless_pathkeys() here, because there
     832             :  * are situations where seeing the raw ordering of the subquery is helpful.
     833             :  * For example, if it returns ORDER BY x DESC, that may prompt us to
     834             :  * construct a mergejoin using DESC order rather than ASC order; but the
     835             :  * right_merge_direction heuristic would have us throw the knowledge away.
     836             :  */
     837             : List *
     838        6700 : convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
     839             :                           List *subquery_pathkeys,
     840             :                           List *subquery_tlist)
     841             : {
     842        6700 :     List       *retval = NIL;
     843        6700 :     int         retvallen = 0;
     844        6700 :     int         outer_query_keys = list_length(root->query_pathkeys);
     845             :     ListCell   *i;
     846             : 
     847        7144 :     foreach(i, subquery_pathkeys)
     848             :     {
     849        1346 :         PathKey    *sub_pathkey = (PathKey *) lfirst(i);
     850        1346 :         EquivalenceClass *sub_eclass = sub_pathkey->pk_eclass;
     851        1346 :         PathKey    *best_pathkey = NULL;
     852             : 
     853        1346 :         if (sub_eclass->ec_has_volatile)
     854             :         {
     855             :             /*
     856             :              * If the sub_pathkey's EquivalenceClass is volatile, then it must
     857             :              * have come from an ORDER BY clause, and we have to match it to
     858             :              * that same targetlist entry.
     859             :              */
     860             :             TargetEntry *tle;
     861             :             Var        *outer_var;
     862             : 
     863           8 :             if (sub_eclass->ec_sortref == 0) /* can't happen */
     864           0 :                 elog(ERROR, "volatile EquivalenceClass has no sortref");
     865           8 :             tle = get_sortgroupref_tle(sub_eclass->ec_sortref, subquery_tlist);
     866             :             Assert(tle);
     867             :             /* Is TLE actually available to the outer query? */
     868           8 :             outer_var = find_var_for_subquery_tle(rel, tle);
     869           8 :             if (outer_var)
     870             :             {
     871             :                 /* We can represent this sub_pathkey */
     872             :                 EquivalenceMember *sub_member;
     873             :                 EquivalenceClass *outer_ec;
     874             : 
     875             :                 Assert(list_length(sub_eclass->ec_members) == 1);
     876           0 :                 sub_member = (EquivalenceMember *) linitial(sub_eclass->ec_members);
     877             : 
     878             :                 /*
     879             :                  * Note: it might look funny to be setting sortref = 0 for a
     880             :                  * reference to a volatile sub_eclass.  However, the
     881             :                  * expression is *not* volatile in the outer query: it's just
     882             :                  * a Var referencing whatever the subquery emitted. (IOW, the
     883             :                  * outer query isn't going to re-execute the volatile
     884             :                  * expression itself.)  So this is okay.  Likewise, it's
     885             :                  * correct to pass nullable_relids = NULL, because we're
     886             :                  * underneath any outer joins appearing in the outer query.
     887             :                  */
     888             :                 outer_ec =
     889           0 :                     get_eclass_for_sort_expr(root,
     890             :                                              (Expr *) outer_var,
     891             :                                              NULL,
     892             :                                              sub_eclass->ec_opfamilies,
     893             :                                              sub_member->em_datatype,
     894             :                                              sub_eclass->ec_collation,
     895             :                                              0,
     896             :                                              rel->relids,
     897             :                                              false);
     898             : 
     899             :                 /*
     900             :                  * If we don't find a matching EC, sub-pathkey isn't
     901             :                  * interesting to the outer query
     902             :                  */
     903           0 :                 if (outer_ec)
     904             :                     best_pathkey =
     905           0 :                         make_canonical_pathkey(root,
     906             :                                                outer_ec,
     907             :                                                sub_pathkey->pk_opfamily,
     908             :                                                sub_pathkey->pk_strategy,
     909           0 :                                                sub_pathkey->pk_nulls_first);
     910             :             }
     911             :         }
     912             :         else
     913             :         {
     914             :             /*
     915             :              * Otherwise, the sub_pathkey's EquivalenceClass could contain
     916             :              * multiple elements (representing knowledge that multiple items
     917             :              * are effectively equal).  Each element might match none, one, or
     918             :              * more of the output columns that are visible to the outer query.
     919             :              * This means we may have multiple possible representations of the
     920             :              * sub_pathkey in the context of the outer query.  Ideally we
     921             :              * would generate them all and put them all into an EC of the
     922             :              * outer query, thereby propagating equality knowledge up to the
     923             :              * outer query.  Right now we cannot do so, because the outer
     924             :              * query's EquivalenceClasses are already frozen when this is
     925             :              * called. Instead we prefer the one that has the highest "score"
     926             :              * (number of EC peers, plus one if it matches the outer
     927             :              * query_pathkeys). This is the most likely to be useful in the
     928             :              * outer query.
     929             :              */
     930        1338 :             int         best_score = -1;
     931             :             ListCell   *j;
     932             : 
     933        2800 :             foreach(j, sub_eclass->ec_members)
     934             :             {
     935        1462 :                 EquivalenceMember *sub_member = (EquivalenceMember *) lfirst(j);
     936        1462 :                 Expr       *sub_expr = sub_member->em_expr;
     937        1462 :                 Oid         sub_expr_type = sub_member->em_datatype;
     938        1462 :                 Oid         sub_expr_coll = sub_eclass->ec_collation;
     939             :                 ListCell   *k;
     940             : 
     941        1462 :                 if (sub_member->em_is_child)
     942          96 :                     continue;   /* ignore children here */
     943             : 
     944        9592 :                 foreach(k, subquery_tlist)
     945             :                 {
     946        8226 :                     TargetEntry *tle = (TargetEntry *) lfirst(k);
     947             :                     Var        *outer_var;
     948             :                     Expr       *tle_expr;
     949             :                     EquivalenceClass *outer_ec;
     950             :                     PathKey    *outer_pk;
     951             :                     int         score;
     952             : 
     953             :                     /* Is TLE actually available to the outer query? */
     954        8226 :                     outer_var = find_var_for_subquery_tle(rel, tle);
     955        8226 :                     if (!outer_var)
     956        5550 :                         continue;
     957             : 
     958             :                     /*
     959             :                      * The targetlist entry is considered to match if it
     960             :                      * matches after sort-key canonicalization.  That is
     961             :                      * needed since the sub_expr has been through the same
     962             :                      * process.
     963             :                      */
     964        2676 :                     tle_expr = canonicalize_ec_expression(tle->expr,
     965             :                                                           sub_expr_type,
     966             :                                                           sub_expr_coll);
     967        2676 :                     if (!equal(tle_expr, sub_expr))
     968        2034 :                         continue;
     969             : 
     970             :                     /* See if we have a matching EC for the TLE */
     971         642 :                     outer_ec = get_eclass_for_sort_expr(root,
     972             :                                                         (Expr *) outer_var,
     973             :                                                         NULL,
     974             :                                                         sub_eclass->ec_opfamilies,
     975             :                                                         sub_expr_type,
     976             :                                                         sub_expr_coll,
     977             :                                                         0,
     978             :                                                         rel->relids,
     979             :                                                         false);
     980             : 
     981             :                     /*
     982             :                      * If we don't find a matching EC, this sub-pathkey isn't
     983             :                      * interesting to the outer query
     984             :                      */
     985         642 :                     if (!outer_ec)
     986         198 :                         continue;
     987             : 
     988         444 :                     outer_pk = make_canonical_pathkey(root,
     989             :                                                       outer_ec,
     990             :                                                       sub_pathkey->pk_opfamily,
     991             :                                                       sub_pathkey->pk_strategy,
     992         444 :                                                       sub_pathkey->pk_nulls_first);
     993             :                     /* score = # of equivalence peers */
     994         444 :                     score = list_length(outer_ec->ec_members) - 1;
     995             :                     /* +1 if it matches the proper query_pathkeys item */
     996         784 :                     if (retvallen < outer_query_keys &&
     997         340 :                         list_nth(root->query_pathkeys, retvallen) == outer_pk)
     998         288 :                         score++;
     999         444 :                     if (score > best_score)
    1000             :                     {
    1001         444 :                         best_pathkey = outer_pk;
    1002         444 :                         best_score = score;
    1003             :                     }
    1004             :                 }
    1005             :             }
    1006             :         }
    1007             : 
    1008             :         /*
    1009             :          * If we couldn't find a representation of this sub_pathkey, we're
    1010             :          * done (we can't use the ones to its right, either).
    1011             :          */
    1012        1346 :         if (!best_pathkey)
    1013         902 :             break;
    1014             : 
    1015             :         /*
    1016             :          * Eliminate redundant ordering info; could happen if outer query
    1017             :          * equivalences subquery keys...
    1018             :          */
    1019         444 :         if (!pathkey_is_redundant(best_pathkey, retval))
    1020             :         {
    1021         444 :             retval = lappend(retval, best_pathkey);
    1022         444 :             retvallen++;
    1023             :         }
    1024             :     }
    1025             : 
    1026        6700 :     return retval;
    1027             : }
    1028             : 
    1029             : /*
    1030             :  * find_var_for_subquery_tle
    1031             :  *
    1032             :  * If the given subquery tlist entry is due to be emitted by the subquery's
    1033             :  * scan node, return a Var for it, else return NULL.
    1034             :  *
    1035             :  * We need this to ensure that we don't return pathkeys describing values
    1036             :  * that are unavailable above the level of the subquery scan.
    1037             :  */
    1038             : static Var *
    1039        8234 : find_var_for_subquery_tle(RelOptInfo *rel, TargetEntry *tle)
    1040             : {
    1041             :     ListCell   *lc;
    1042             : 
    1043             :     /* If the TLE is resjunk, it's certainly not visible to the outer query */
    1044        8234 :     if (tle->resjunk)
    1045           0 :         return NULL;
    1046             : 
    1047             :     /* Search the rel's targetlist to see what it will return */
    1048       23780 :     foreach(lc, rel->reltarget->exprs)
    1049             :     {
    1050       18222 :         Var        *var = (Var *) lfirst(lc);
    1051             : 
    1052             :         /* Ignore placeholders */
    1053       18222 :         if (!IsA(var, Var))
    1054          16 :             continue;
    1055             :         Assert(var->varno == rel->relid);
    1056             : 
    1057             :         /* If we find a Var referencing this TLE, we're good */
    1058       18206 :         if (var->varattno == tle->resno)
    1059        2676 :             return copyObject(var); /* Make a copy for safety */
    1060             :     }
    1061        5558 :     return NULL;
    1062             : }
    1063             : 
    1064             : /*
    1065             :  * build_join_pathkeys
    1066             :  *    Build the path keys for a join relation constructed by mergejoin or
    1067             :  *    nestloop join.  This is normally the same as the outer path's keys.
    1068             :  *
    1069             :  *    EXCEPTION: in a FULL or RIGHT join, we cannot treat the result as
    1070             :  *    having the outer path's path keys, because null lefthand rows may be
    1071             :  *    inserted at random points.  It must be treated as unsorted.
    1072             :  *
    1073             :  *    We truncate away any pathkeys that are uninteresting for higher joins.
    1074             :  *
    1075             :  * 'joinrel' is the join relation that paths are being formed for
    1076             :  * 'jointype' is the join type (inner, left, full, etc)
    1077             :  * 'outer_pathkeys' is the list of the current outer path's path keys
    1078             :  *
    1079             :  * Returns the list of new path keys.
    1080             :  */
    1081             : List *
    1082      841588 : build_join_pathkeys(PlannerInfo *root,
    1083             :                     RelOptInfo *joinrel,
    1084             :                     JoinType jointype,
    1085             :                     List *outer_pathkeys)
    1086             : {
    1087      841588 :     if (jointype == JOIN_FULL || jointype == JOIN_RIGHT)
    1088      122432 :         return NIL;
    1089             : 
    1090             :     /*
    1091             :      * This used to be quite a complex bit of code, but now that all pathkey
    1092             :      * sublists start out life canonicalized, we don't have to do a darn thing
    1093             :      * here!
    1094             :      *
    1095             :      * We do, however, need to truncate the pathkeys list, since it may
    1096             :      * contain pathkeys that were useful for forming this joinrel but are
    1097             :      * uninteresting to higher levels.
    1098             :      */
    1099      719156 :     return truncate_useless_pathkeys(root, joinrel, outer_pathkeys);
    1100             : }
    1101             : 
    1102             : /****************************************************************************
    1103             :  *      PATHKEYS AND SORT CLAUSES
    1104             :  ****************************************************************************/
    1105             : 
    1106             : /*
    1107             :  * make_pathkeys_for_sortclauses
    1108             :  *      Generate a pathkeys list that represents the sort order specified
    1109             :  *      by a list of SortGroupClauses
    1110             :  *
    1111             :  * The resulting PathKeys are always in canonical form.  (Actually, there
    1112             :  * is no longer any code anywhere that creates non-canonical PathKeys.)
    1113             :  *
    1114             :  * We assume that root->nullable_baserels is the set of base relids that could
    1115             :  * have gone to NULL below the SortGroupClause expressions.  This is okay if
    1116             :  * the expressions came from the query's top level (ORDER BY, DISTINCT, etc)
    1117             :  * and if this function is only invoked after deconstruct_jointree.  In the
    1118             :  * future we might have to make callers pass in the appropriate
    1119             :  * nullable-relids set, but for now it seems unnecessary.
    1120             :  *
    1121             :  * 'sortclauses' is a list of SortGroupClause nodes
    1122             :  * 'tlist' is the targetlist to find the referenced tlist entries in
    1123             :  */
    1124             : List *
    1125      337592 : make_pathkeys_for_sortclauses(PlannerInfo *root,
    1126             :                               List *sortclauses,
    1127             :                               List *tlist)
    1128             : {
    1129      337592 :     List       *pathkeys = NIL;
    1130             :     ListCell   *l;
    1131             : 
    1132      395588 :     foreach(l, sortclauses)
    1133             :     {
    1134       57996 :         SortGroupClause *sortcl = (SortGroupClause *) lfirst(l);
    1135             :         Expr       *sortkey;
    1136             :         PathKey    *pathkey;
    1137             : 
    1138       57996 :         sortkey = (Expr *) get_sortgroupclause_expr(sortcl, tlist);
    1139             :         Assert(OidIsValid(sortcl->sortop));
    1140      115992 :         pathkey = make_pathkey_from_sortop(root,
    1141             :                                            sortkey,
    1142             :                                            root->nullable_baserels,
    1143             :                                            sortcl->sortop,
    1144       57996 :                                            sortcl->nulls_first,
    1145             :                                            sortcl->tleSortGroupRef,
    1146             :                                            true);
    1147             : 
    1148             :         /* Canonical form eliminates redundant ordering keys */
    1149       57996 :         if (!pathkey_is_redundant(pathkey, pathkeys))
    1150       57116 :             pathkeys = lappend(pathkeys, pathkey);
    1151             :     }
    1152      337592 :     return pathkeys;
    1153             : }
    1154             : 
    1155             : /****************************************************************************
    1156             :  *      PATHKEYS AND MERGECLAUSES
    1157             :  ****************************************************************************/
    1158             : 
    1159             : /*
    1160             :  * initialize_mergeclause_eclasses
    1161             :  *      Set the EquivalenceClass links in a mergeclause restrictinfo.
    1162             :  *
    1163             :  * RestrictInfo contains fields in which we may cache pointers to
    1164             :  * EquivalenceClasses for the left and right inputs of the mergeclause.
    1165             :  * (If the mergeclause is a true equivalence clause these will be the
    1166             :  * same EquivalenceClass, otherwise not.)  If the mergeclause is either
    1167             :  * used to generate an EquivalenceClass, or derived from an EquivalenceClass,
    1168             :  * then it's easy to set up the left_ec and right_ec members --- otherwise,
    1169             :  * this function should be called to set them up.  We will generate new
    1170             :  * EquivalenceClauses if necessary to represent the mergeclause's left and
    1171             :  * right sides.
    1172             :  *
    1173             :  * Note this is called before EC merging is complete, so the links won't
    1174             :  * necessarily point to canonical ECs.  Before they are actually used for
    1175             :  * anything, update_mergeclause_eclasses must be called to ensure that
    1176             :  * they've been updated to point to canonical ECs.
    1177             :  */
    1178             : void
    1179       41646 : initialize_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
    1180             : {
    1181       41646 :     Expr       *clause = restrictinfo->clause;
    1182             :     Oid         lefttype,
    1183             :                 righttype;
    1184             : 
    1185             :     /* Should be a mergeclause ... */
    1186             :     Assert(restrictinfo->mergeopfamilies != NIL);
    1187             :     /* ... with links not yet set */
    1188             :     Assert(restrictinfo->left_ec == NULL);
    1189             :     Assert(restrictinfo->right_ec == NULL);
    1190             : 
    1191             :     /* Need the declared input types of the operator */
    1192       41646 :     op_input_types(((OpExpr *) clause)->opno, &lefttype, &righttype);
    1193             : 
    1194             :     /* Find or create a matching EquivalenceClass for each side */
    1195       41646 :     restrictinfo->left_ec =
    1196       41646 :         get_eclass_for_sort_expr(root,
    1197       41646 :                                  (Expr *) get_leftop(clause),
    1198             :                                  restrictinfo->nullable_relids,
    1199             :                                  restrictinfo->mergeopfamilies,
    1200             :                                  lefttype,
    1201             :                                  ((OpExpr *) clause)->inputcollid,
    1202             :                                  0,
    1203             :                                  NULL,
    1204             :                                  true);
    1205       41646 :     restrictinfo->right_ec =
    1206       41646 :         get_eclass_for_sort_expr(root,
    1207       41646 :                                  (Expr *) get_rightop(clause),
    1208             :                                  restrictinfo->nullable_relids,
    1209             :                                  restrictinfo->mergeopfamilies,
    1210             :                                  righttype,
    1211             :                                  ((OpExpr *) clause)->inputcollid,
    1212             :                                  0,
    1213             :                                  NULL,
    1214             :                                  true);
    1215       41646 : }
    1216             : 
    1217             : /*
    1218             :  * update_mergeclause_eclasses
    1219             :  *      Make the cached EquivalenceClass links valid in a mergeclause
    1220             :  *      restrictinfo.
    1221             :  *
    1222             :  * These pointers should have been set by process_equivalence or
    1223             :  * initialize_mergeclause_eclasses, but they might have been set to
    1224             :  * non-canonical ECs that got merged later.  Chase up to the canonical
    1225             :  * merged parent if so.
    1226             :  */
    1227             : void
    1228     2194864 : update_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
    1229             : {
    1230             :     /* Should be a merge clause ... */
    1231             :     Assert(restrictinfo->mergeopfamilies != NIL);
    1232             :     /* ... with pointers already set */
    1233             :     Assert(restrictinfo->left_ec != NULL);
    1234             :     Assert(restrictinfo->right_ec != NULL);
    1235             : 
    1236             :     /* Chase up to the top as needed */
    1237     2194864 :     while (restrictinfo->left_ec->ec_merged)
    1238           0 :         restrictinfo->left_ec = restrictinfo->left_ec->ec_merged;
    1239     2195284 :     while (restrictinfo->right_ec->ec_merged)
    1240         420 :         restrictinfo->right_ec = restrictinfo->right_ec->ec_merged;
    1241     2194864 : }
    1242             : 
    1243             : /*
    1244             :  * find_mergeclauses_for_outer_pathkeys
    1245             :  *    This routine attempts to find a list of mergeclauses that can be
    1246             :  *    used with a specified ordering for the join's outer relation.
    1247             :  *    If successful, it returns a list of mergeclauses.
    1248             :  *
    1249             :  * 'pathkeys' is a pathkeys list showing the ordering of an outer-rel path.
    1250             :  * 'restrictinfos' is a list of mergejoinable restriction clauses for the
    1251             :  *          join relation being formed, in no particular order.
    1252             :  *
    1253             :  * The restrictinfos must be marked (via outer_is_left) to show which side
    1254             :  * of each clause is associated with the current outer path.  (See
    1255             :  * select_mergejoin_clauses())
    1256             :  *
    1257             :  * The result is NIL if no merge can be done, else a maximal list of
    1258             :  * usable mergeclauses (represented as a list of their restrictinfo nodes).
    1259             :  * The list is ordered to match the pathkeys, as required for execution.
    1260             :  */
    1261             : List *
    1262      829304 : find_mergeclauses_for_outer_pathkeys(PlannerInfo *root,
    1263             :                                      List *pathkeys,
    1264             :                                      List *restrictinfos)
    1265             : {
    1266      829304 :     List       *mergeclauses = NIL;
    1267             :     ListCell   *i;
    1268             : 
    1269             :     /* make sure we have eclasses cached in the clauses */
    1270     1647668 :     foreach(i, restrictinfos)
    1271             :     {
    1272      818364 :         RestrictInfo *rinfo = (RestrictInfo *) lfirst(i);
    1273             : 
    1274      818364 :         update_mergeclause_eclasses(root, rinfo);
    1275             :     }
    1276             : 
    1277     1311440 :     foreach(i, pathkeys)
    1278             :     {
    1279      581504 :         PathKey    *pathkey = (PathKey *) lfirst(i);
    1280      581504 :         EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
    1281      581504 :         List       *matched_restrictinfos = NIL;
    1282             :         ListCell   *j;
    1283             : 
    1284             :         /*----------
    1285             :          * A mergejoin clause matches a pathkey if it has the same EC.
    1286             :          * If there are multiple matching clauses, take them all.  In plain
    1287             :          * inner-join scenarios we expect only one match, because
    1288             :          * equivalence-class processing will have removed any redundant
    1289             :          * mergeclauses.  However, in outer-join scenarios there might be
    1290             :          * multiple matches.  An example is
    1291             :          *
    1292             :          *  select * from a full join b
    1293             :          *      on a.v1 = b.v1 and a.v2 = b.v2 and a.v1 = b.v2;
    1294             :          *
    1295             :          * Given the pathkeys ({a.v1}, {a.v2}) it is okay to return all three
    1296             :          * clauses (in the order a.v1=b.v1, a.v1=b.v2, a.v2=b.v2) and indeed
    1297             :          * we *must* do so or we will be unable to form a valid plan.
    1298             :          *
    1299             :          * We expect that the given pathkeys list is canonical, which means
    1300             :          * no two members have the same EC, so it's not possible for this
    1301             :          * code to enter the same mergeclause into the result list twice.
    1302             :          *
    1303             :          * It's possible that multiple matching clauses might have different
    1304             :          * ECs on the other side, in which case the order we put them into our
    1305             :          * result makes a difference in the pathkeys required for the inner
    1306             :          * input rel.  However this routine hasn't got any info about which
    1307             :          * order would be best, so we don't worry about that.
    1308             :          *
    1309             :          * It's also possible that the selected mergejoin clauses produce
    1310             :          * a noncanonical ordering of pathkeys for the inner side, ie, we
    1311             :          * might select clauses that reference b.v1, b.v2, b.v1 in that
    1312             :          * order.  This is not harmful in itself, though it suggests that
    1313             :          * the clauses are partially redundant.  Since the alternative is
    1314             :          * to omit mergejoin clauses and thereby possibly fail to generate a
    1315             :          * plan altogether, we live with it.  make_inner_pathkeys_for_merge()
    1316             :          * has to delete duplicates when it constructs the inner pathkeys
    1317             :          * list, and we also have to deal with such cases specially in
    1318             :          * create_mergejoin_plan().
    1319             :          *----------
    1320             :          */
    1321     1244034 :         foreach(j, restrictinfos)
    1322             :         {
    1323      662530 :             RestrictInfo *rinfo = (RestrictInfo *) lfirst(j);
    1324             :             EquivalenceClass *clause_ec;
    1325             : 
    1326     1325060 :             clause_ec = rinfo->outer_is_left ?
    1327      662530 :                 rinfo->left_ec : rinfo->right_ec;
    1328      662530 :             if (clause_ec == pathkey_ec)
    1329      484876 :                 matched_restrictinfos = lappend(matched_restrictinfos, rinfo);
    1330             :         }
    1331             : 
    1332             :         /*
    1333             :          * If we didn't find a mergeclause, we're done --- any additional
    1334             :          * sort-key positions in the pathkeys are useless.  (But we can still
    1335             :          * mergejoin if we found at least one mergeclause.)
    1336             :          */
    1337      581504 :         if (matched_restrictinfos == NIL)
    1338       99368 :             break;
    1339             : 
    1340             :         /*
    1341             :          * If we did find usable mergeclause(s) for this sort-key position,
    1342             :          * add them to result list.
    1343             :          */
    1344      482136 :         mergeclauses = list_concat(mergeclauses, matched_restrictinfos);
    1345             :     }
    1346             : 
    1347      829304 :     return mergeclauses;
    1348             : }
    1349             : 
    1350             : /*
    1351             :  * select_outer_pathkeys_for_merge
    1352             :  *    Builds a pathkey list representing a possible sort ordering
    1353             :  *    that can be used with the given mergeclauses.
    1354             :  *
    1355             :  * 'mergeclauses' is a list of RestrictInfos for mergejoin clauses
    1356             :  *          that will be used in a merge join.
    1357             :  * 'joinrel' is the join relation we are trying to construct.
    1358             :  *
    1359             :  * The restrictinfos must be marked (via outer_is_left) to show which side
    1360             :  * of each clause is associated with the current outer path.  (See
    1361             :  * select_mergejoin_clauses())
    1362             :  *
    1363             :  * Returns a pathkeys list that can be applied to the outer relation.
    1364             :  *
    1365             :  * Since we assume here that a sort is required, there is no particular use
    1366             :  * in matching any available ordering of the outerrel.  (joinpath.c has an
    1367             :  * entirely separate code path for considering sort-free mergejoins.)  Rather,
    1368             :  * it's interesting to try to match the requested query_pathkeys so that a
    1369             :  * second output sort may be avoided; and failing that, we try to list "more
    1370             :  * popular" keys (those with the most unmatched EquivalenceClass peers)
    1371             :  * earlier, in hopes of making the resulting ordering useful for as many
    1372             :  * higher-level mergejoins as possible.
    1373             :  */
    1374             : List *
    1375      296128 : select_outer_pathkeys_for_merge(PlannerInfo *root,
    1376             :                                 List *mergeclauses,
    1377             :                                 RelOptInfo *joinrel)
    1378             : {
    1379      296128 :     List       *pathkeys = NIL;
    1380      296128 :     int         nClauses = list_length(mergeclauses);
    1381             :     EquivalenceClass **ecs;
    1382             :     int        *scores;
    1383             :     int         necs;
    1384             :     ListCell   *lc;
    1385             :     int         j;
    1386             : 
    1387             :     /* Might have no mergeclauses */
    1388      296128 :     if (nClauses == 0)
    1389       60234 :         return NIL;
    1390             : 
    1391             :     /*
    1392             :      * Make arrays of the ECs used by the mergeclauses (dropping any
    1393             :      * duplicates) and their "popularity" scores.
    1394             :      */
    1395      235894 :     ecs = (EquivalenceClass **) palloc(nClauses * sizeof(EquivalenceClass *));
    1396      235894 :     scores = (int *) palloc(nClauses * sizeof(int));
    1397      235894 :     necs = 0;
    1398             : 
    1399      488774 :     foreach(lc, mergeclauses)
    1400             :     {
    1401      252880 :         RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
    1402             :         EquivalenceClass *oeclass;
    1403             :         int         score;
    1404             :         ListCell   *lc2;
    1405             : 
    1406             :         /* get the outer eclass */
    1407      252880 :         update_mergeclause_eclasses(root, rinfo);
    1408             : 
    1409      252880 :         if (rinfo->outer_is_left)
    1410      129494 :             oeclass = rinfo->left_ec;
    1411             :         else
    1412      123386 :             oeclass = rinfo->right_ec;
    1413             : 
    1414             :         /* reject duplicates */
    1415      269930 :         for (j = 0; j < necs; j++)
    1416             :         {
    1417       18426 :             if (ecs[j] == oeclass)
    1418        1376 :                 break;
    1419             :         }
    1420      252880 :         if (j < necs)
    1421        1376 :             continue;
    1422             : 
    1423             :         /* compute score */
    1424      251504 :         score = 0;
    1425      771880 :         foreach(lc2, oeclass->ec_members)
    1426             :         {
    1427      520376 :             EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
    1428             : 
    1429             :             /* Potential future join partner? */
    1430      520376 :             if (!em->em_is_const && !em->em_is_child &&
    1431      440388 :                 !bms_overlap(em->em_relids, joinrel->relids))
    1432       35286 :                 score++;
    1433             :         }
    1434             : 
    1435      251504 :         ecs[necs] = oeclass;
    1436      251504 :         scores[necs] = score;
    1437      251504 :         necs++;
    1438             :     }
    1439             : 
    1440             :     /*
    1441             :      * Find out if we have all the ECs mentioned in query_pathkeys; if so we
    1442             :      * can generate a sort order that's also useful for final output. There is
    1443             :      * no percentage in a partial match, though, so we have to have 'em all.
    1444             :      */
    1445      235894 :     if (root->query_pathkeys)
    1446             :     {
    1447      149952 :         foreach(lc, root->query_pathkeys)
    1448             :         {
    1449      141506 :             PathKey    *query_pathkey = (PathKey *) lfirst(lc);
    1450      141506 :             EquivalenceClass *query_ec = query_pathkey->pk_eclass;
    1451             : 
    1452      278146 :             for (j = 0; j < necs; j++)
    1453             :             {
    1454      148090 :                 if (ecs[j] == query_ec)
    1455       11450 :                     break;      /* found match */
    1456             :             }
    1457      141506 :             if (j >= necs)
    1458      130056 :                 break;          /* didn't find match */
    1459             :         }
    1460             :         /* if we got to the end of the list, we have them all */
    1461      138502 :         if (lc == NULL)
    1462             :         {
    1463             :             /* copy query_pathkeys as starting point for our output */
    1464        8446 :             pathkeys = list_copy(root->query_pathkeys);
    1465             :             /* mark their ECs as already-emitted */
    1466       17140 :             foreach(lc, root->query_pathkeys)
    1467             :             {
    1468        8694 :                 PathKey    *query_pathkey = (PathKey *) lfirst(lc);
    1469        8694 :                 EquivalenceClass *query_ec = query_pathkey->pk_eclass;
    1470             : 
    1471       10298 :                 for (j = 0; j < necs; j++)
    1472             :                 {
    1473       10298 :                     if (ecs[j] == query_ec)
    1474             :                     {
    1475        8694 :                         scores[j] = -1;
    1476        8694 :                         break;
    1477             :                     }
    1478             :                 }
    1479             :             }
    1480             :         }
    1481             :     }
    1482             : 
    1483             :     /*
    1484             :      * Add remaining ECs to the list in popularity order, using a default sort
    1485             :      * ordering.  (We could use qsort() here, but the list length is usually
    1486             :      * so small it's not worth it.)
    1487             :      */
    1488             :     for (;;)
    1489      242810 :     {
    1490             :         int         best_j;
    1491             :         int         best_score;
    1492             :         EquivalenceClass *ec;
    1493             :         PathKey    *pathkey;
    1494             : 
    1495      478704 :         best_j = 0;
    1496      478704 :         best_score = scores[0];
    1497      524854 :         for (j = 1; j < necs; j++)
    1498             :         {
    1499       46150 :             if (scores[j] > best_score)
    1500             :             {
    1501       14006 :                 best_j = j;
    1502       14006 :                 best_score = scores[j];
    1503             :             }
    1504             :         }
    1505      478704 :         if (best_score < 0)
    1506      235894 :             break;              /* all done */
    1507      242810 :         ec = ecs[best_j];
    1508      242810 :         scores[best_j] = -1;
    1509      242810 :         pathkey = make_canonical_pathkey(root,
    1510             :                                          ec,
    1511      242810 :                                          linitial_oid(ec->ec_opfamilies),
    1512             :                                          BTLessStrategyNumber,
    1513             :                                          false);
    1514             :         /* can't be redundant because no duplicate ECs */
    1515             :         Assert(!pathkey_is_redundant(pathkey, pathkeys));
    1516      242810 :         pathkeys = lappend(pathkeys, pathkey);
    1517             :     }
    1518             : 
    1519      235894 :     pfree(ecs);
    1520      235894 :     pfree(scores);
    1521             : 
    1522      235894 :     return pathkeys;
    1523             : }
    1524             : 
    1525             : /*
    1526             :  * make_inner_pathkeys_for_merge
    1527             :  *    Builds a pathkey list representing the explicit sort order that
    1528             :  *    must be applied to an inner path to make it usable with the
    1529             :  *    given mergeclauses.
    1530             :  *
    1531             :  * 'mergeclauses' is a list of RestrictInfos for the mergejoin clauses
    1532             :  *          that will be used in a merge join, in order.
    1533             :  * 'outer_pathkeys' are the already-known canonical pathkeys for the outer
    1534             :  *          side of the join.
    1535             :  *
    1536             :  * The restrictinfos must be marked (via outer_is_left) to show which side
    1537             :  * of each clause is associated with the current outer path.  (See
    1538             :  * select_mergejoin_clauses())
    1539             :  *
    1540             :  * Returns a pathkeys list that can be applied to the inner relation.
    1541             :  *
    1542             :  * Note that it is not this routine's job to decide whether sorting is
    1543             :  * actually needed for a particular input path.  Assume a sort is necessary;
    1544             :  * just make the keys, eh?
    1545             :  */
    1546             : List *
    1547      443896 : make_inner_pathkeys_for_merge(PlannerInfo *root,
    1548             :                               List *mergeclauses,
    1549             :                               List *outer_pathkeys)
    1550             : {
    1551      443896 :     List       *pathkeys = NIL;
    1552             :     EquivalenceClass *lastoeclass;
    1553             :     PathKey    *opathkey;
    1554             :     ListCell   *lc;
    1555             :     ListCell   *lop;
    1556             : 
    1557      443896 :     lastoeclass = NULL;
    1558      443896 :     opathkey = NULL;
    1559      443896 :     lop = list_head(outer_pathkeys);
    1560             : 
    1561      928410 :     foreach(lc, mergeclauses)
    1562             :     {
    1563      484514 :         RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
    1564             :         EquivalenceClass *oeclass;
    1565             :         EquivalenceClass *ieclass;
    1566             :         PathKey    *pathkey;
    1567             : 
    1568      484514 :         update_mergeclause_eclasses(root, rinfo);
    1569             : 
    1570      484514 :         if (rinfo->outer_is_left)
    1571             :         {
    1572      236928 :             oeclass = rinfo->left_ec;
    1573      236928 :             ieclass = rinfo->right_ec;
    1574             :         }
    1575             :         else
    1576             :         {
    1577      247586 :             oeclass = rinfo->right_ec;
    1578      247586 :             ieclass = rinfo->left_ec;
    1579             :         }
    1580             : 
    1581             :         /* outer eclass should match current or next pathkeys */
    1582             :         /* we check this carefully for debugging reasons */
    1583      484514 :         if (oeclass != lastoeclass)
    1584             :         {
    1585      481782 :             if (!lop)
    1586           0 :                 elog(ERROR, "too few pathkeys for mergeclauses");
    1587      481782 :             opathkey = (PathKey *) lfirst(lop);
    1588      481782 :             lop = lnext(outer_pathkeys, lop);
    1589      481782 :             lastoeclass = opathkey->pk_eclass;
    1590      481782 :             if (oeclass != lastoeclass)
    1591           0 :                 elog(ERROR, "outer pathkeys do not match mergeclause");
    1592             :         }
    1593             : 
    1594             :         /*
    1595             :          * Often, we'll have same EC on both sides, in which case the outer
    1596             :          * pathkey is also canonical for the inner side, and we can skip a
    1597             :          * useless search.
    1598             :          */
    1599      484514 :         if (ieclass == oeclass)
    1600      281894 :             pathkey = opathkey;
    1601             :         else
    1602      202620 :             pathkey = make_canonical_pathkey(root,
    1603             :                                              ieclass,
    1604             :                                              opathkey->pk_opfamily,
    1605             :                                              opathkey->pk_strategy,
    1606      202620 :                                              opathkey->pk_nulls_first);
    1607             : 
    1608             :         /*
    1609             :          * Don't generate redundant pathkeys (which can happen if multiple
    1610             :          * mergeclauses refer to the same EC).  Because we do this, the output
    1611             :          * pathkey list isn't necessarily ordered like the mergeclauses, which
    1612             :          * complicates life for create_mergejoin_plan().  But if we didn't,
    1613             :          * we'd have a noncanonical sort key list, which would be bad; for one
    1614             :          * reason, it certainly wouldn't match any available sort order for
    1615             :          * the input relation.
    1616             :          */
    1617      484514 :         if (!pathkey_is_redundant(pathkey, pathkeys))
    1618      484398 :             pathkeys = lappend(pathkeys, pathkey);
    1619             :     }
    1620             : 
    1621      443896 :     return pathkeys;
    1622             : }
    1623             : 
    1624             : /*
    1625             :  * trim_mergeclauses_for_inner_pathkeys
    1626             :  *    This routine trims a list of mergeclauses to include just those that
    1627             :  *    work with a specified ordering for the join's inner relation.
    1628             :  *
    1629             :  * 'mergeclauses' is a list of RestrictInfos for mergejoin clauses for the
    1630             :  *          join relation being formed, in an order known to work for the
    1631             :  *          currently-considered sort ordering of the join's outer rel.
    1632             :  * 'pathkeys' is a pathkeys list showing the ordering of an inner-rel path;
    1633             :  *          it should be equal to, or a truncation of, the result of
    1634             :  *          make_inner_pathkeys_for_merge for these mergeclauses.
    1635             :  *
    1636             :  * What we return will be a prefix of the given mergeclauses list.
    1637             :  *
    1638             :  * We need this logic because make_inner_pathkeys_for_merge's result isn't
    1639             :  * necessarily in the same order as the mergeclauses.  That means that if we
    1640             :  * consider an inner-rel pathkey list that is a truncation of that result,
    1641             :  * we might need to drop mergeclauses even though they match a surviving inner
    1642             :  * pathkey.  This happens when they are to the right of a mergeclause that
    1643             :  * matches a removed inner pathkey.
    1644             :  *
    1645             :  * The mergeclauses must be marked (via outer_is_left) to show which side
    1646             :  * of each clause is associated with the current outer path.  (See
    1647             :  * select_mergejoin_clauses())
    1648             :  */
    1649             : List *
    1650        1028 : trim_mergeclauses_for_inner_pathkeys(PlannerInfo *root,
    1651             :                                      List *mergeclauses,
    1652             :                                      List *pathkeys)
    1653             : {
    1654        1028 :     List       *new_mergeclauses = NIL;
    1655             :     PathKey    *pathkey;
    1656             :     EquivalenceClass *pathkey_ec;
    1657             :     bool        matched_pathkey;
    1658             :     ListCell   *lip;
    1659             :     ListCell   *i;
    1660             : 
    1661             :     /* No pathkeys => no mergeclauses (though we don't expect this case) */
    1662        1028 :     if (pathkeys == NIL)
    1663           0 :         return NIL;
    1664             :     /* Initialize to consider first pathkey */
    1665        1028 :     lip = list_head(pathkeys);
    1666        1028 :     pathkey = (PathKey *) lfirst(lip);
    1667        1028 :     pathkey_ec = pathkey->pk_eclass;
    1668        1028 :     lip = lnext(pathkeys, lip);
    1669        1028 :     matched_pathkey = false;
    1670             : 
    1671             :     /* Scan mergeclauses to see how many we can use */
    1672        2056 :     foreach(i, mergeclauses)
    1673             :     {
    1674        2056 :         RestrictInfo *rinfo = (RestrictInfo *) lfirst(i);
    1675             :         EquivalenceClass *clause_ec;
    1676             : 
    1677             :         /* Assume we needn't do update_mergeclause_eclasses again here */
    1678             : 
    1679             :         /* Check clause's inner-rel EC against current pathkey */
    1680        4112 :         clause_ec = rinfo->outer_is_left ?
    1681        2056 :             rinfo->right_ec : rinfo->left_ec;
    1682             : 
    1683             :         /* If we don't have a match, attempt to advance to next pathkey */
    1684        2056 :         if (clause_ec != pathkey_ec)
    1685             :         {
    1686             :             /* If we had no clauses matching this inner pathkey, must stop */
    1687        1028 :             if (!matched_pathkey)
    1688           0 :                 break;
    1689             : 
    1690             :             /* Advance to next inner pathkey, if any */
    1691        1028 :             if (lip == NULL)
    1692        1028 :                 break;
    1693           0 :             pathkey = (PathKey *) lfirst(lip);
    1694           0 :             pathkey_ec = pathkey->pk_eclass;
    1695           0 :             lip = lnext(pathkeys, lip);
    1696           0 :             matched_pathkey = false;
    1697             :         }
    1698             : 
    1699             :         /* If mergeclause matches current inner pathkey, we can use it */
    1700        1028 :         if (clause_ec == pathkey_ec)
    1701             :         {
    1702        1028 :             new_mergeclauses = lappend(new_mergeclauses, rinfo);
    1703        1028 :             matched_pathkey = true;
    1704             :         }
    1705             :         else
    1706             :         {
    1707             :             /* Else, no hope of adding any more mergeclauses */
    1708           0 :             break;
    1709             :         }
    1710             :     }
    1711             : 
    1712        1028 :     return new_mergeclauses;
    1713             : }
    1714             : 
    1715             : 
    1716             : /****************************************************************************
    1717             :  *      PATHKEY USEFULNESS CHECKS
    1718             :  *
    1719             :  * We only want to remember as many of the pathkeys of a path as have some
    1720             :  * potential use, either for subsequent mergejoins or for meeting the query's
    1721             :  * requested output ordering.  This ensures that add_path() won't consider
    1722             :  * a path to have a usefully different ordering unless it really is useful.
    1723             :  * These routines check for usefulness of given pathkeys.
    1724             :  ****************************************************************************/
    1725             : 
    1726             : /*
    1727             :  * pathkeys_useful_for_merging
    1728             :  *      Count the number of pathkeys that may be useful for mergejoins
    1729             :  *      above the given relation.
    1730             :  *
    1731             :  * We consider a pathkey potentially useful if it corresponds to the merge
    1732             :  * ordering of either side of any joinclause for the rel.  This might be
    1733             :  * overoptimistic, since joinclauses that require different other relations
    1734             :  * might never be usable at the same time, but trying to be exact is likely
    1735             :  * to be more trouble than it's worth.
    1736             :  *
    1737             :  * To avoid doubling the number of mergejoin paths considered, we would like
    1738             :  * to consider only one of the two scan directions (ASC or DESC) as useful
    1739             :  * for merging for any given target column.  The choice is arbitrary unless
    1740             :  * one of the directions happens to match an ORDER BY key, in which case
    1741             :  * that direction should be preferred, in hopes of avoiding a final sort step.
    1742             :  * right_merge_direction() implements this heuristic.
    1743             :  */
    1744             : static int
    1745     1309460 : pathkeys_useful_for_merging(PlannerInfo *root, RelOptInfo *rel, List *pathkeys)
    1746             : {
    1747     1309460 :     int         useful = 0;
    1748             :     ListCell   *i;
    1749             : 
    1750     1617226 :     foreach(i, pathkeys)
    1751             :     {
    1752      817004 :         PathKey    *pathkey = (PathKey *) lfirst(i);
    1753      817004 :         bool        matched = false;
    1754             :         ListCell   *j;
    1755             : 
    1756             :         /* If "wrong" direction, not useful for merging */
    1757      817004 :         if (!right_merge_direction(root, pathkey))
    1758      167742 :             break;
    1759             : 
    1760             :         /*
    1761             :          * First look into the EquivalenceClass of the pathkey, to see if
    1762             :          * there are any members not yet joined to the rel.  If so, it's
    1763             :          * surely possible to generate a mergejoin clause using them.
    1764             :          */
    1765      968766 :         if (rel->has_eclass_joins &&
    1766      319504 :             eclass_useful_for_merging(root, pathkey->pk_eclass, rel))
    1767      171466 :             matched = true;
    1768             :         else
    1769             :         {
    1770             :             /*
    1771             :              * Otherwise search the rel's joininfo list, which contains
    1772             :              * non-EquivalenceClass-derivable join clauses that might
    1773             :              * nonetheless be mergejoinable.
    1774             :              */
    1775      762352 :             foreach(j, rel->joininfo)
    1776             :             {
    1777      420856 :                 RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(j);
    1778             : 
    1779      420856 :                 if (restrictinfo->mergeopfamilies == NIL)
    1780       85440 :                     continue;
    1781      335416 :                 update_mergeclause_eclasses(root, restrictinfo);
    1782             : 
    1783      335416 :                 if (pathkey->pk_eclass == restrictinfo->left_ec ||
    1784      273888 :                     pathkey->pk_eclass == restrictinfo->right_ec)
    1785             :                 {
    1786      136300 :                     matched = true;
    1787      136300 :                     break;
    1788             :                 }
    1789             :             }
    1790             :         }
    1791             : 
    1792             :         /*
    1793             :          * If we didn't find a mergeclause, we're done --- any additional
    1794             :          * sort-key positions in the pathkeys are useless.  (But we can still
    1795             :          * mergejoin if we found at least one mergeclause.)
    1796             :          */
    1797      649262 :         if (matched)
    1798      307766 :             useful++;
    1799             :         else
    1800      341496 :             break;
    1801             :     }
    1802             : 
    1803     1309460 :     return useful;
    1804             : }
    1805             : 
    1806             : /*
    1807             :  * right_merge_direction
    1808             :  *      Check whether the pathkey embodies the preferred sort direction
    1809             :  *      for merging its target column.
    1810             :  */
    1811             : static bool
    1812      817004 : right_merge_direction(PlannerInfo *root, PathKey *pathkey)
    1813             : {
    1814             :     ListCell   *l;
    1815             : 
    1816     1290238 :     foreach(l, root->query_pathkeys)
    1817             :     {
    1818      612370 :         PathKey    *query_pathkey = (PathKey *) lfirst(l);
    1819             : 
    1820      612370 :         if (pathkey->pk_eclass == query_pathkey->pk_eclass &&
    1821      139136 :             pathkey->pk_opfamily == query_pathkey->pk_opfamily)
    1822             :         {
    1823             :             /*
    1824             :              * Found a matching query sort column.  Prefer this pathkey's
    1825             :              * direction iff it matches.  Note that we ignore pk_nulls_first,
    1826             :              * which means that a sort might be needed anyway ... but we still
    1827             :              * want to prefer only one of the two possible directions, and we
    1828             :              * might as well use this one.
    1829             :              */
    1830      139136 :             return (pathkey->pk_strategy == query_pathkey->pk_strategy);
    1831             :         }
    1832             :     }
    1833             : 
    1834             :     /* If no matching ORDER BY request, prefer the ASC direction */
    1835      677868 :     return (pathkey->pk_strategy == BTLessStrategyNumber);
    1836             : }
    1837             : 
    1838             : /*
    1839             :  * pathkeys_useful_for_ordering
    1840             :  *      Count the number of pathkeys that are useful for meeting the
    1841             :  *      query's requested output ordering.
    1842             :  *
    1843             :  * Because we the have the possibility of incremental sort, a prefix list of
    1844             :  * keys is potentially useful for improving the performance of the requested
    1845             :  * ordering. Thus we return 0, if no valuable keys are found, or the number
    1846             :  * of leading keys shared by the list and the requested ordering..
    1847             :  */
    1848             : static int
    1849     1309460 : pathkeys_useful_for_ordering(PlannerInfo *root, List *pathkeys)
    1850             : {
    1851             :     int         n_common_pathkeys;
    1852             : 
    1853     1309460 :     if (root->query_pathkeys == NIL)
    1854      564618 :         return 0;               /* no special ordering requested */
    1855             : 
    1856      744842 :     if (pathkeys == NIL)
    1857      280632 :         return 0;               /* unordered path */
    1858             : 
    1859      464210 :     (void) pathkeys_count_contained_in(root->query_pathkeys, pathkeys,
    1860             :                                        &n_common_pathkeys);
    1861             : 
    1862      464210 :     return n_common_pathkeys;
    1863             : }
    1864             : 
    1865             : /*
    1866             :  * truncate_useless_pathkeys
    1867             :  *      Shorten the given pathkey list to just the useful pathkeys.
    1868             :  */
    1869             : List *
    1870     1309460 : truncate_useless_pathkeys(PlannerInfo *root,
    1871             :                           RelOptInfo *rel,
    1872             :                           List *pathkeys)
    1873             : {
    1874             :     int         nuseful;
    1875             :     int         nuseful2;
    1876             : 
    1877     1309460 :     nuseful = pathkeys_useful_for_merging(root, rel, pathkeys);
    1878     1309460 :     nuseful2 = pathkeys_useful_for_ordering(root, pathkeys);
    1879     1309460 :     if (nuseful2 > nuseful)
    1880       84028 :         nuseful = nuseful2;
    1881             : 
    1882             :     /*
    1883             :      * Note: not safe to modify input list destructively, but we can avoid
    1884             :      * copying the list if we're not actually going to change it
    1885             :      */
    1886     1309460 :     if (nuseful == 0)
    1887      927554 :         return NIL;
    1888      381906 :     else if (nuseful == list_length(pathkeys))
    1889      368462 :         return pathkeys;
    1890             :     else
    1891       13444 :         return list_truncate(list_copy(pathkeys), nuseful);
    1892             : }
    1893             : 
    1894             : /*
    1895             :  * has_useful_pathkeys
    1896             :  *      Detect whether the specified rel could have any pathkeys that are
    1897             :  *      useful according to truncate_useless_pathkeys().
    1898             :  *
    1899             :  * This is a cheap test that lets us skip building pathkeys at all in very
    1900             :  * simple queries.  It's OK to err in the direction of returning "true" when
    1901             :  * there really aren't any usable pathkeys, but erring in the other direction
    1902             :  * is bad --- so keep this in sync with the routines above!
    1903             :  *
    1904             :  * We could make the test more complex, for example checking to see if any of
    1905             :  * the joinclauses are really mergejoinable, but that likely wouldn't win
    1906             :  * often enough to repay the extra cycles.  Queries with neither a join nor
    1907             :  * a sort are reasonably common, though, so this much work seems worthwhile.
    1908             :  */
    1909             : bool
    1910      518034 : has_useful_pathkeys(PlannerInfo *root, RelOptInfo *rel)
    1911             : {
    1912      518034 :     if (rel->joininfo != NIL || rel->has_eclass_joins)
    1913      269296 :         return true;            /* might be able to use pathkeys for merging */
    1914      248738 :     if (root->query_pathkeys != NIL)
    1915       39414 :         return true;            /* might be able to use them for ordering */
    1916      209324 :     return false;               /* definitely useless */
    1917             : }

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