Invert and rename flag variable to improve code readability.
No change in functionality. Per discussion with Robert.
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@ -42,7 +42,7 @@ static List *select_mergejoin_clauses(PlannerInfo *root,
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RelOptInfo *innerrel,
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List *restrictlist,
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JoinType jointype,
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bool *have_nonmergeable_clause);
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bool *mergejoin_allowed);
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/*
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@ -78,7 +78,7 @@ add_paths_to_joinrel(PlannerInfo *root,
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List *restrictlist)
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{
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List *mergeclause_list = NIL;
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bool have_nonmergeable_clause = false;
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bool mergejoin_allowed = true;
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/*
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* Find potential mergejoin clauses. We can skip this if we are not
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@ -93,13 +93,13 @@ add_paths_to_joinrel(PlannerInfo *root,
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innerrel,
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restrictlist,
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jointype,
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&have_nonmergeable_clause);
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&mergejoin_allowed);
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/*
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* 1. Consider mergejoin paths where both relations must be explicitly
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* sorted. Skip this if we can't mergejoin.
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*/
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if (!have_nonmergeable_clause)
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if (mergejoin_allowed)
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sort_inner_and_outer(root, joinrel, outerrel, innerrel,
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restrictlist, mergeclause_list, jointype, sjinfo);
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@ -108,9 +108,9 @@ add_paths_to_joinrel(PlannerInfo *root,
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* sorted. This includes both nestloops and mergejoins where the outer
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* path is already ordered. Again, skip this if we can't mergejoin.
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* (That's okay because we know that nestloop can't handle right/full
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* joins at all, so it wouldn't work in those cases either.)
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* joins at all, so it wouldn't work in the prohibited cases either.)
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*/
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if (!have_nonmergeable_clause)
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if (mergejoin_allowed)
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match_unsorted_outer(root, joinrel, outerrel, innerrel,
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restrictlist, mergeclause_list, jointype, sjinfo);
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@ -127,7 +127,7 @@ add_paths_to_joinrel(PlannerInfo *root,
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* those made by match_unsorted_outer when add_paths_to_joinrel() is
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* invoked with the two rels given in the other order.
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*/
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if (!have_nonmergeable_clause)
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if (mergejoin_allowed)
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match_unsorted_inner(root, joinrel, outerrel, innerrel,
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restrictlist, mergeclause_list, jointype, sjinfo);
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#endif
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@ -927,10 +927,14 @@ best_appendrel_indexscan(PlannerInfo *root, RelOptInfo *rel,
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* Select mergejoin clauses that are usable for a particular join.
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* Returns a list of RestrictInfo nodes for those clauses.
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*
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* *have_nonmergeable_clause is set TRUE if this is a right/full join and
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* there are nonmergejoinable join clauses. The executor's mergejoin
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* machinery cannot handle such cases, so we have to avoid generating a
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* mergejoin plan.
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* *mergejoin_allowed is normally set to TRUE, but it is set to FALSE if
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* this is a right/full join and there are nonmergejoinable join clauses.
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* The executor's mergejoin machinery cannot handle such cases, so we have
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* to avoid generating a mergejoin plan. (Note that this flag does NOT
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* consider whether there are actually any mergejoinable clauses. This is
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* correct because in some cases we need to build a clauseless mergejoin.
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* Simply returning NIL is therefore not enough to distinguish safe from
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* unsafe cases.)
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*
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* We also mark each selected RestrictInfo to show which side is currently
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* being considered as outer. These are transient markings that are only
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@ -947,14 +951,13 @@ select_mergejoin_clauses(PlannerInfo *root,
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RelOptInfo *innerrel,
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List *restrictlist,
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JoinType jointype,
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bool *have_nonmergeable_clause)
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bool *mergejoin_allowed)
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{
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List *result_list = NIL;
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bool isouterjoin = IS_OUTER_JOIN(jointype);
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bool have_nonmergeable_joinclause = false;
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ListCell *l;
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*have_nonmergeable_clause = false;
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foreach(l, restrictlist)
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{
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RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
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@ -962,7 +965,7 @@ select_mergejoin_clauses(PlannerInfo *root,
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/*
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* If processing an outer join, only use its own join clauses in the
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* merge. For inner joins we can use pushed-down clauses too. (Note:
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* we don't set have_nonmergeable_clause here because pushed-down
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* we don't set have_nonmergeable_joinclause here because pushed-down
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* clauses will become otherquals not joinquals.)
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*/
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if (isouterjoin && restrictinfo->is_pushed_down)
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@ -979,7 +982,7 @@ select_mergejoin_clauses(PlannerInfo *root,
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* FALSE.)
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*/
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if (!restrictinfo->clause || !IsA(restrictinfo->clause, Const))
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*have_nonmergeable_clause = true;
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have_nonmergeable_joinclause = true;
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continue; /* not mergejoinable */
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}
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@ -988,7 +991,7 @@ select_mergejoin_clauses(PlannerInfo *root,
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*/
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if (!clause_sides_match_join(restrictinfo, outerrel, innerrel))
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{
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*have_nonmergeable_clause = true;
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have_nonmergeable_joinclause = true;
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continue; /* no good for these input relations */
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}
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@ -1017,7 +1020,7 @@ select_mergejoin_clauses(PlannerInfo *root,
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if (EC_MUST_BE_REDUNDANT(restrictinfo->left_ec) ||
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EC_MUST_BE_REDUNDANT(restrictinfo->right_ec))
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{
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*have_nonmergeable_clause = true;
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have_nonmergeable_joinclause = true;
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continue; /* can't handle redundant eclasses */
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}
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@ -1025,18 +1028,16 @@ select_mergejoin_clauses(PlannerInfo *root,
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}
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/*
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* If it is not a right/full join then we don't need to insist on all the
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* joinclauses being mergejoinable, so reset the flag. This simplifies
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* the logic in add_paths_to_joinrel.
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* Report whether mergejoin is allowed (see comment at top of function).
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*/
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switch (jointype)
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{
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case JOIN_RIGHT:
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case JOIN_FULL:
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*mergejoin_allowed = !have_nonmergeable_joinclause;
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break;
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default:
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/* otherwise, it's OK to have nonmergeable join quals */
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*have_nonmergeable_clause = false;
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*mergejoin_allowed = true;
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break;
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}
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