Make inheritance planning logic a little simpler and clearer,
hopefully even a little faster.
This commit is contained in:
parent
996659f255
commit
38db5fab29
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.84 2000/06/18 22:44:09 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.85 2000/06/20 04:22:21 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -94,7 +94,8 @@ planner(Query *parse)
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* Basically, this routine does the stuff that should only be done once
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* per Query object. It then calls union_planner, which may be called
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* recursively on the same Query node in order to handle UNIONs and/or
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* inheritance. subquery_planner is called recursively from subselect.c.
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* inheritance. subquery_planner is called recursively from subselect.c
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* to handle sub-Query nodes found within the query's expressions.
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*
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* prepunion.c uses an unholy combination of calling union_planner when
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* recursing on the primary Query node, or subquery_planner when recursing
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@ -107,10 +108,6 @@ planner(Query *parse)
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Plan *
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subquery_planner(Query *parse, double tuple_fraction)
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{
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List *l;
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List *rangetable = parse->rtable;
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RangeTblEntry *rangeTblEntry;
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/*
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* A HAVING clause without aggregates is equivalent to a WHERE clause
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* (except it can only refer to grouped fields). If there are no aggs
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@ -142,18 +139,6 @@ subquery_planner(Query *parse, double tuple_fraction)
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parse->qual = eval_const_expressions(parse->qual);
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parse->havingQual = eval_const_expressions(parse->havingQual);
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/*
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* If the query is going to look for subclasses, but no subclasses
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* actually exist, then we can optimise away the union that would
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* otherwise happen and thus save some time.
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*/
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foreach(l, rangetable)
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{
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rangeTblEntry = (RangeTblEntry *)lfirst(l);
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if (rangeTblEntry->inh && !has_subclass(rangeTblEntry->relid))
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rangeTblEntry->inh = FALSE;
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}
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/*
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* Canonicalize the qual, and convert it to implicit-AND format.
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*
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@ -257,10 +242,11 @@ union_planner(Query *parse,
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List *group_pathkeys;
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List *sort_pathkeys;
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Index rt_index;
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List *inheritors;
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if (parse->unionClause)
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{
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result_plan = (Plan *) plan_union_queries(parse);
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result_plan = plan_union_queries(parse);
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/* XXX do we need to do this? bjm 12/19/97 */
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tlist = preprocess_targetlist(tlist,
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parse->commandType,
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@ -269,9 +255,8 @@ union_planner(Query *parse,
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/*
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* We leave current_pathkeys NIL indicating we do not know sort
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* order. Actually, for a normal UNION we have done an explicit
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* sort; ought to change interface to plan_union_queries to pass
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* that info back!
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* order. This is correct for the appended-together subplan
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* results, even if the subplans themselves produced sorted results.
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*/
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/*
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@ -283,7 +268,8 @@ union_planner(Query *parse,
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sort_pathkeys = make_pathkeys_for_sortclauses(parse->sortClause,
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tlist);
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}
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else if ((rt_index = first_inherit_rt_entry(rangetable)) != -1)
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else if (find_inheritable_rt_entry(rangetable,
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&rt_index, &inheritors))
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{
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List *sub_tlist;
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@ -296,8 +282,8 @@ union_planner(Query *parse,
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/*
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* Recursively plan the subqueries needed for inheritance
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*/
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result_plan = (Plan *) plan_inherit_queries(parse, sub_tlist,
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rt_index);
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result_plan = plan_inherit_queries(parse, sub_tlist,
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rt_index, inheritors);
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/*
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* Fix up outer target list. NOTE: unlike the case for
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.50 2000/05/30 00:49:49 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/optimizer/prep/prepunion.c,v 1.51 2000/06/20 04:22:16 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -33,15 +33,12 @@ typedef struct
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Oid new_relid;
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} fix_parsetree_attnums_context;
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static List *plan_inherit_query(Relids relids, Index rt_index,
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RangeTblEntry *rt_entry, Query *parse, List *tlist,
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List **union_rtentriesPtr);
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static RangeTblEntry *new_rangetable_entry(Oid new_relid,
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RangeTblEntry *old_entry);
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static void fix_parsetree_attnums(Index rt_index, Oid old_relid,
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Oid new_relid, Query *parsetree);
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static bool fix_parsetree_attnums_walker(Node *node,
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fix_parsetree_attnums_context *context);
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static RangeTblEntry *new_rangetable_entry(Oid new_relid,
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RangeTblEntry *old_entry);
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static Append *make_append(List *appendplans, List *unionrtables,
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Index rt_index,
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List *inheritrtable, List *tlist);
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@ -52,9 +49,13 @@ static Append *make_append(List *appendplans, List *unionrtables,
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*
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* Plans the queries for a given UNION.
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*
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* Returns a list containing a list of plans and a list of rangetables
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* Returns an Append plan that combines the results of the unioned queries.
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* Note that Append output is correct for UNION ALL, but caller still needs
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* to take care of sort/unique processing if it's a plain UNION. We set or
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* clear the Query's fields so that the right things will happen back in
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* union_planner. (This control structure is an unholy mess...)
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*/
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Append *
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Plan *
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plan_union_queries(Query *parse)
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{
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List *union_plans = NIL,
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parse->havingQual = NULL;
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parse->hasAggs = false;
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return make_append(union_plans,
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union_rts,
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0,
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NULL,
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parse->targetList);
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return (Plan *) make_append(union_plans,
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union_rts,
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0,
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NIL,
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parse->targetList);
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}
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/*
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* plan_inherit_queries
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*
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* Plans the queries for an inheritance tree rooted at a parent relation.
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*
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* Inputs:
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* parse = parent parse tree
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* root = parent parse tree
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* tlist = target list for inheritance subqueries (not same as parent's!)
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* rt_index = rangetable index for current inheritance item
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* inheritors = list of OIDs of the target rel plus all its descendants
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*
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* Returns an APPEND node that forms the result of performing the given
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* query for each member relation of the inheritance group.
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* operations just once above the APPEND node. The given tlist has been
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* modified appropriately to remove group/aggregate expressions, but the
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* Query node still has the relevant fields set. We remove them in the
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* copies used for subplans (see plan_inherit_query).
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* copies used for subplans.
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*
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* NOTE: this can be invoked recursively if more than one inheritance wildcard
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* is present. At each level of recursion, the first wildcard remaining in
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* the rangetable is expanded.
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*
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* NOTE: don't bother optimizing this routine for the case that the target
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* rel has no children. We won't get here unless find_inheritable_rt_entry
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* found at least two members in the inheritance group, so an APPEND is
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* certainly necessary.
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*/
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Append *
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plan_inherit_queries(Query *parse, List *tlist, Index rt_index)
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{
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List *rangetable = parse->rtable;
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RangeTblEntry *rt_entry = rt_fetch(rt_index, rangetable);
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List *inheritrtable = NIL;
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List *union_relids;
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List *union_plans;
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/* Make a list of the target relid plus all its descendants */
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union_relids = find_all_inheritors(rt_entry->relid);
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/*
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* Remove the flag for this relation, since we're about to handle it.
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* XXX destructive change to parent parse tree, but necessary to
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* prevent infinite recursion.
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*/
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rt_entry->inh = false;
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union_plans = plan_inherit_query(union_relids, rt_index, rt_entry,
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parse, tlist, &inheritrtable);
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return make_append(union_plans,
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NULL,
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rt_index,
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inheritrtable,
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((Plan *) lfirst(union_plans))->targetlist);
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}
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/*
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* plan_inherit_query
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* Returns a list of plans for 'relids', plus a list of range table entries
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* in *union_rtentriesPtr.
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*/
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static List *
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plan_inherit_query(Relids relids,
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Index rt_index,
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RangeTblEntry *rt_entry,
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Query *root,
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List *tlist,
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List **union_rtentriesPtr)
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Plan *
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plan_inherit_queries(Query *root, List *tlist,
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Index rt_index, List *inheritors)
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{
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RangeTblEntry *rt_entry = rt_fetch(rt_index, root->rtable);
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List *union_plans = NIL;
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List *union_rtentries = NIL;
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List *save_tlist = root->targetList;
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/*
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* Avoid making copies of the root's tlist, which we aren't going to
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* use anyway (we are going to make copies of the passed tlist,
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* instead).
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* instead). This is purely a space-saving hack. Note we restore
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* the root's tlist before exiting.
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*/
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root->targetList = NIL;
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else
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tuple_fraction = -1.0; /* default behavior is OK (I think) */
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foreach(i, relids)
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foreach(i, inheritors)
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{
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int relid = lfirsti(i);
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Oid relid = lfirsti(i);
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/*
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* Make a modifiable copy of the original query, and replace the
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* target rangetable entry with a new one identifying this child
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* table.
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* target rangetable entry in it with a new one identifying this
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* child table. The new rtentry is marked inh = false --- this
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* is essential to prevent infinite recursion when the subquery
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* is rescanned by find_inheritable_rt_entry!
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*/
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Query *new_root = copyObject(root);
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RangeTblEntry *new_rt_entry = new_rangetable_entry(relid,
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rt_entry);
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new_rt_entry->inh = false;
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rt_store(rt_index, new_root->rtable, new_rt_entry);
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/*
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@ -368,6 +341,8 @@ plan_inherit_query(Relids relids,
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new_root->sortClause = NIL;
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new_root->groupClause = NIL;
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new_root->havingQual = NULL;
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new_root->limitOffset = NULL; /* LIMIT's probably unsafe too */
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new_root->limitCount = NULL;
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new_root->hasAggs = false; /* shouldn't be any left ... */
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/*
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relid,
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new_root);
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/*
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* Plan the subquery by recursively calling union_planner().
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* Add plan and child rtentry to lists for APPEND.
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*/
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union_plans = lappend(union_plans,
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union_planner(new_root, tuple_fraction));
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union_rtentries = lappend(union_rtentries, new_rt_entry);
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}
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/* Restore root's tlist */
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root->targetList = save_tlist;
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*union_rtentriesPtr = union_rtentries;
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return union_plans;
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/* Construct the finished Append plan. */
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return (Plan *) make_append(union_plans,
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NIL,
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rt_index,
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union_rtentries,
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((Plan *) lfirst(union_plans))->targetlist);
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}
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/*
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@ -420,10 +404,11 @@ find_all_inheritors(Oid parentrel)
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currentchildren = find_inheritance_children(currentrel);
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/*
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* Add to the queue only those children not already seen. This
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* could probably be simplified to a plain nconc, because our
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* inheritance relationships should always be a strict tree, no?
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* Should never find any matches, ISTM...
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* Add to the queue only those children not already seen.
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* This avoids making duplicate entries in case of multiple
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* inheritance paths from the same parent. (It'll also keep
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* us from getting into an infinite loop, though theoretically
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* there can't be any cycles in the inheritance graph anyway.)
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*/
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currentchildren = set_differencei(currentchildren, examined_relids);
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unexamined_relids = LispUnioni(unexamined_relids, currentchildren);
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@ -433,29 +418,71 @@ find_all_inheritors(Oid parentrel)
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}
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/*
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* first_inherit_rt_entry -
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* find_inheritable_rt_entry -
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* Given a rangetable, find the first rangetable entry that represents
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* an inheritance set.
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*
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* Returns a rangetable index (1..n).
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* Returns -1 if no matches
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* If successful, set *rt_index to the index (1..n) of the entry,
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* set *inheritors to a list of the relation OIDs of the set,
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* and return TRUE.
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*
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* If there is no entry that requires inheritance processing,
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* return FALSE.
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*
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* NOTE: We return the inheritors list so that plan_inherit_queries doesn't
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* have to compute it again.
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*
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* NOTE: We clear the inh flag in any entries that have it set but turn
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* out not to have any actual inheritance children. This is an efficiency
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* hack to avoid having to repeat the inheritance checks if the list is
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* scanned again (as will happen during expansion of any subsequent entry
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* that does have inheritance children). Although modifying the input
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* rangetable in-place may seem uncool, there's no reason not to do it,
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* since any re-examination of the entry would just come to the same
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* conclusion that the table has no children.
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*/
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int
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first_inherit_rt_entry(List *rangetable)
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bool
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find_inheritable_rt_entry(List *rangetable,
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Index *rt_index,
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List **inheritors)
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{
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int count = 0;
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Index count = 0;
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List *temp;
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foreach(temp, rangetable)
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{
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RangeTblEntry *rt_entry = lfirst(temp);
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RangeTblEntry *rt_entry = (RangeTblEntry *) lfirst(temp);
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List *inhs;
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count++;
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if (rt_entry->inh)
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return count;
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/* Ignore non-inheritable RT entries */
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if (! rt_entry->inh)
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continue;
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/* Fast path for common case of childless table */
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if (! has_subclass(rt_entry->relid))
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{
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rt_entry->inh = false;
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continue;
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}
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/* Scan for all members of inheritance set */
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inhs = find_all_inheritors(rt_entry->relid);
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/*
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* Check that there's at least one descendant, else treat as
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* no-child case. This could happen despite above has_subclass()
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* check, if table once had a child but no longer does.
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*/
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if (lnext(inhs) == NIL)
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{
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rt_entry->inh = false;
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continue;
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}
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/* OK, found our boy */
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*rt_index = count;
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*inheritors = inhs;
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return true;
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}
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return -1;
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return false;
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}
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/*
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|
@ -483,7 +510,7 @@ new_rangetable_entry(Oid new_relid, RangeTblEntry *old_entry)
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* 'new_relid'.
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*
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* The parsetree is MODIFIED IN PLACE. This is OK only because
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* plan_inherit_query made a copy of the tree for us to hack upon.
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* plan_inherit_queries made a copy of the tree for us to hack upon.
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*/
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static void
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fix_parsetree_attnums(Index rt_index,
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|
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|
@ -9,7 +9,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.57 2000/06/17 21:48:51 tgl Exp $
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* $Header: /cvsroot/pgsql/src/backend/optimizer/util/plancat.c,v 1.58 2000/06/20 04:22:14 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -261,6 +261,11 @@ join_selectivity(Oid functionObjectId,
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*
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* Returns an integer list containing the OIDs of all relations which
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* inherit *directly* from the relation with OID 'inhparent'.
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*
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* XXX might be a good idea to create an index on pg_inherits' inhparent
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* field, so that we can use an indexscan instead of sequential scan here.
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* However, in typical databases pg_inherits won't have enough entries to
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* justify an indexscan...
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*/
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List *
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find_inheritance_children(Oid inhparent)
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|
@ -269,12 +274,19 @@ find_inheritance_children(Oid inhparent)
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{0, Anum_pg_inherits_inhparent, F_OIDEQ}
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};
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HeapTuple inheritsTuple;
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List *list = NIL;
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Relation relation;
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HeapScanDesc scan;
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List *list = NIL;
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HeapTuple inheritsTuple;
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Oid inhrelid;
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/*
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* Can skip the scan if pg_class shows the relation has never had
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* a subclass.
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||||
*/
|
||||
if (! has_subclass(inhparent))
|
||||
return NIL;
|
||||
|
||||
fmgr_info(F_OIDEQ, &key[0].sk_func);
|
||||
key[0].sk_nargs = key[0].sk_func.fn_nargs;
|
||||
key[0].sk_argument = ObjectIdGetDatum(inhparent);
|
||||
|
@ -292,14 +304,16 @@ find_inheritance_children(Oid inhparent)
|
|||
}
|
||||
|
||||
/*
|
||||
* has_subclass -
|
||||
* has_subclass
|
||||
*
|
||||
* In the current implementation, has_subclass returns whether a
|
||||
* particular class *might* have a subclass. It will not return the
|
||||
* correct result if a class had a subclass which was later dropped.
|
||||
* This is because relhassubclass in pg_class is not updated,
|
||||
* possibly because of efficiency and/or concurrency concerns.
|
||||
* Currently has_subclass is only used as an efficiency hack, so this
|
||||
* is ok.
|
||||
* This is because relhassubclass in pg_class is not updated when a
|
||||
* subclass is dropped, primarily because of concurrency concerns.
|
||||
*
|
||||
* Currently has_subclass is only used as an efficiency hack to skip
|
||||
* unnecessary inheritance searches, so this is OK.
|
||||
*/
|
||||
bool
|
||||
has_subclass(Oid relationId)
|
||||
|
|
|
@ -7,7 +7,7 @@
|
|||
* Portions Copyright (c) 1996-2000, PostgreSQL, Inc
|
||||
* Portions Copyright (c) 1994, Regents of the University of California
|
||||
*
|
||||
* $Id: prep.h,v 1.22 2000/06/08 22:37:51 momjian Exp $
|
||||
* $Id: prep.h,v 1.23 2000/06/20 04:22:13 tgl Exp $
|
||||
*
|
||||
*-------------------------------------------------------------------------
|
||||
*/
|
||||
|
@ -33,8 +33,10 @@ extern List *preprocess_targetlist(List *tlist, int command_type,
|
|||
* prototypes for prepunion.c
|
||||
*/
|
||||
extern List *find_all_inheritors(Oid parentrel);
|
||||
extern int first_inherit_rt_entry(List *rangetable);
|
||||
extern Append *plan_union_queries(Query *parse);
|
||||
extern Append *plan_inherit_queries(Query *parse, List *tlist, Index rt_index);
|
||||
extern bool find_inheritable_rt_entry(List *rangetable,
|
||||
Index *rt_index, List **inheritors);
|
||||
extern Plan *plan_inherit_queries(Query *root, List *tlist,
|
||||
Index rt_index, List *inheritors);
|
||||
extern Plan *plan_union_queries(Query *parse);
|
||||
|
||||
#endif /* PREP_H */
|
||||
|
|
Loading…
Reference in New Issue