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Revise parameterized-path mechanism to fix assorted issues.
This patch adjusts the treatment of parameterized paths so that all paths with the same parameterization (same set of required outer rels) for the same relation will have the same rowcount estimate. We cache the rowcount estimates to ensure that property, and hopefully save a few cycles too. Doing this makes it practical for add_path_precheck to operate without a rowcount estimate: it need only assume that paths with different parameterizations never dominate each other, which is close enough to true anyway for coarse filtering, because normally a more-parameterized path should yield fewer rows thanks to having more join clauses to apply. In add_path, we do the full nine yards of comparing rowcount estimates along with everything else, so that we can discard parameterized paths that don't actually have an advantage. This fixes some issues I'd found with add_path rejecting parameterized paths on the grounds that they were more expensive than not-parameterized ones, even though they yielded many fewer rows and hence would be cheaper once subsequent joining was considered. To make the same-rowcounts assumption valid, we have to require that any parameterized path enforce *all* join clauses that could be obtained from the particular set of outer rels, even if not all of them are useful for indexing. This is required at both base scans and joins. It's a good thing anyway since the net impact is that join quals are checked at the lowest practical level in the join tree. Hence, discard the original rather ad-hoc mechanism for choosing parameterization joinquals, and build a better one that has a more principled rule for when clauses can be moved. The original rule was actually buggy anyway for lack of knowledge about which relations are part of an outer join's outer side; getting this right requires adding an outer_relids field to RestrictInfo.
This commit is contained in:
Tom Lane
@@ -66,17 +66,20 @@ extern int constraint_exclusion;
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extern double clamp_row_est(double nrows);
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extern double index_pages_fetched(double tuples_fetched, BlockNumber pages,
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double index_pages, PlannerInfo *root);
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extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel);
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extern void cost_seqscan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
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ParamPathInfo *param_info);
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extern void cost_index(IndexPath *path, PlannerInfo *root,
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double loop_count);
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extern void cost_bitmap_heap_scan(Path *path, PlannerInfo *root, RelOptInfo *baserel,
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ParamPathInfo *param_info,
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Path *bitmapqual, double loop_count);
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extern void cost_bitmap_and_node(BitmapAndPath *path, PlannerInfo *root);
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extern void cost_bitmap_or_node(BitmapOrPath *path, PlannerInfo *root);
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extern void cost_bitmap_tree_node(Path *path, Cost *cost, Selectivity *selec);
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extern void cost_tidscan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel, List *tidquals);
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extern void cost_subqueryscan(Path *path, RelOptInfo *baserel);
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extern void cost_subqueryscan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel, ParamPathInfo *param_info);
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extern void cost_functionscan(Path *path, PlannerInfo *root,
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RelOptInfo *baserel);
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extern void cost_valuesscan(Path *path, PlannerInfo *root,
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@@ -149,6 +152,15 @@ extern void compute_semi_anti_join_factors(PlannerInfo *root,
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List *restrictlist,
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SemiAntiJoinFactors *semifactors);
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extern void set_baserel_size_estimates(PlannerInfo *root, RelOptInfo *rel);
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extern double get_parameterized_baserel_size(PlannerInfo *root,
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RelOptInfo *rel,
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List *param_clauses);
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extern double get_parameterized_joinrel_size(PlannerInfo *root,
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RelOptInfo *rel,
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double outer_rows,
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double inner_rows,
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SpecialJoinInfo *sjinfo,
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List *restrict_clauses);
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extern void set_joinrel_size_estimates(PlannerInfo *root, RelOptInfo *rel,
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RelOptInfo *outer_rel,
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RelOptInfo *inner_rel,
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@@ -30,7 +30,8 @@ extern bool add_path_precheck(RelOptInfo *parent_rel,
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Cost startup_cost, Cost total_cost,
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List *pathkeys, Relids required_outer);
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extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel);
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extern Path *create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
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Relids required_outer);
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extern IndexPath *create_index_path(PlannerInfo *root,
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IndexOptInfo *index,
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List *indexclauses,
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@@ -45,6 +46,7 @@ extern IndexPath *create_index_path(PlannerInfo *root,
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extern BitmapHeapPath *create_bitmap_heap_path(PlannerInfo *root,
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RelOptInfo *rel,
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Path *bitmapqual,
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Relids required_outer,
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double loop_count);
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extern BitmapAndPath *create_bitmap_and_path(PlannerInfo *root,
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RelOptInfo *rel,
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@@ -54,16 +56,19 @@ extern BitmapOrPath *create_bitmap_or_path(PlannerInfo *root,
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List *bitmapquals);
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extern TidPath *create_tidscan_path(PlannerInfo *root, RelOptInfo *rel,
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List *tidquals);
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extern AppendPath *create_append_path(RelOptInfo *rel, List *subpaths);
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extern AppendPath *create_append_path(RelOptInfo *rel, List *subpaths,
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Relids required_outer);
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extern MergeAppendPath *create_merge_append_path(PlannerInfo *root,
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RelOptInfo *rel,
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List *subpaths,
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List *pathkeys);
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List *pathkeys,
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Relids required_outer);
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extern ResultPath *create_result_path(List *quals);
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extern MaterialPath *create_material_path(RelOptInfo *rel, Path *subpath);
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extern UniquePath *create_unique_path(PlannerInfo *root, RelOptInfo *rel,
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Path *subpath, SpecialJoinInfo *sjinfo);
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extern Path *create_subqueryscan_path(RelOptInfo *rel, List *pathkeys);
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extern Path *create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel,
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List *pathkeys, Relids required_outer);
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extern Path *create_functionscan_path(PlannerInfo *root, RelOptInfo *rel);
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extern Path *create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel);
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extern Path *create_ctescan_path(PlannerInfo *root, RelOptInfo *rel);
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@@ -71,7 +76,7 @@ extern Path *create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel);
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extern ForeignPath *create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel,
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double rows, Cost startup_cost, Cost total_cost,
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List *pathkeys,
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Relids required_outer, List *param_clauses,
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Relids required_outer,
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List *fdw_private);
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extern Relids calc_nestloop_required_outer(Path *outer_path, Path *inner_path);
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@@ -115,6 +120,10 @@ extern HashPath *create_hashjoin_path(PlannerInfo *root,
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Relids required_outer,
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List *hashclauses);
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extern Path *reparameterize_path(PlannerInfo *root, Path *path,
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Relids required_outer,
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double loop_count);
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/*
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* prototypes for relnode.c
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*/
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@@ -129,5 +138,19 @@ extern RelOptInfo *build_join_rel(PlannerInfo *root,
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RelOptInfo *inner_rel,
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SpecialJoinInfo *sjinfo,
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List **restrictlist_ptr);
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extern AppendRelInfo *find_childrel_appendrelinfo(PlannerInfo *root,
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RelOptInfo *rel);
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extern ParamPathInfo *get_baserel_parampathinfo(PlannerInfo *root,
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RelOptInfo *baserel,
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Relids required_outer);
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extern ParamPathInfo *get_joinrel_parampathinfo(PlannerInfo *root,
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RelOptInfo *joinrel,
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Path *outer_path,
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Path *inner_path,
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SpecialJoinInfo *sjinfo,
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Relids required_outer,
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List **restrict_clauses);
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extern ParamPathInfo *get_appendrel_parampathinfo(RelOptInfo *appendrel,
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Relids required_outer);
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#endif /* PATHNODE_H */
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@@ -114,8 +114,8 @@ extern EquivalenceClass *get_eclass_for_sort_expr(PlannerInfo *root,
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bool create_it);
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extern void generate_base_implied_equalities(PlannerInfo *root);
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extern List *generate_join_implied_equalities(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outer_rel,
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Relids join_relids,
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Relids outer_relids,
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RelOptInfo *inner_rel);
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extern bool exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2);
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extern void add_child_rel_equivalences(PlannerInfo *root,
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@@ -134,6 +134,7 @@ extern bool has_relevant_eclass_joinclause(PlannerInfo *root,
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RelOptInfo *rel1);
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extern bool eclass_useful_for_merging(EquivalenceClass *eclass,
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RelOptInfo *rel);
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extern bool is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist);
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/*
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* pathkeys.c
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@@ -19,13 +19,14 @@
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/* Convenience macro for the common case of a valid-everywhere qual */
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#define make_simple_restrictinfo(clause) \
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make_restrictinfo(clause, true, false, false, NULL, NULL)
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make_restrictinfo(clause, true, false, false, NULL, NULL, NULL)
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extern RestrictInfo *make_restrictinfo(Expr *clause,
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bool is_pushed_down,
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bool outerjoin_delayed,
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bool pseudoconstant,
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Relids required_relids,
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Relids outer_relids,
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Relids nullable_relids);
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extern List *make_restrictinfo_from_bitmapqual(Path *bitmapqual,
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bool is_pushed_down,
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@@ -40,7 +41,9 @@ extern List *extract_actual_clauses(List *restrictinfo_list,
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extern void extract_actual_join_clauses(List *restrictinfo_list,
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List **joinquals,
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List **otherquals);
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extern List *select_nonredundant_join_clauses(List *restrictinfo_list,
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List *reference_list);
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extern bool join_clause_is_movable_to(RestrictInfo *rinfo, Index baserelid);
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extern bool join_clause_is_movable_into(RestrictInfo *rinfo,
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Relids currentrelids,
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Relids current_and_outer);
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#endif /* RESTRICTINFO_H */
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