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Invent "join domains" to replace the below_outer_join hack.

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EquivalenceClasses are now understood as applying within a "join
domain", which is a set of inner-joined relations (possibly underneath
an outer join).  We no longer need to treat an EC from below an outer
join as a second-class citizen.

I have hopes of eventually being able to treat outer-join clauses via
EquivalenceClasses, by means of only applying deductions within the
EC's join domain.  There are still problems in the way of that, though,
so for now the reconsider_outer_join_clause logic is still here.

I haven't been able to get rid of RestrictInfo.is_pushed_down either,
but I wonder if that could be recast using JoinDomains.

I had to hack one test case in postgres_fdw.sql to make it still test
what it was meant to, because postgres_fdw is inconsistent about
how it deals with quals containing non-shippable expressions; see
https://postgr.es/m/1691374.1671659838@sss.pgh.pa.us.  That should
be improved, but I don't think it's within the scope of this patch
series.

Patch by me; thanks to Richard Guo for review.

Discussion: https://postgr.es/m/830269.1656693747@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2023-01-30 13:50:25 -05:00
parent b448f1c8d8
commit 3bef56e116
12 changed files with 269 additions and 193 deletions
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10
src/backend/optimizer/plan/planner.c
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@@ -625,6 +625,7 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
root->init_plans = NIL;
root->cte_plan_ids = NIL;
root->multiexpr_params = NIL;
root->join_domains = NIL;
root->eq_classes = NIL;
root->ec_merging_done = false;
root->last_rinfo_serial = 0;
@@ -654,6 +655,13 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
root->non_recursive_path = NULL;
root->partColsUpdated = false;
/*
* Create the top-level join domain. This won't have valid contents until
* deconstruct_jointree fills it in, but the node needs to exist before
* that so we can build EquivalenceClasses referencing it.
*/
root->join_domains = list_make1(makeNode(JoinDomain));
/*
* If there is a WITH list, process each WITH query and either convert it
* to RTE_SUBQUERY RTE(s) or build an initplan SubPlan structure for it.
@@ -6534,6 +6542,7 @@ plan_cluster_use_sort(Oid tableOid, Oid indexOid)
root->query_level = 1;
root->planner_cxt = CurrentMemoryContext;
root->wt_param_id = -1;
root->join_domains = list_make1(makeNode(JoinDomain));
/* Build a minimal RTE for the rel */
rte = makeNode(RangeTblEntry);
@@ -6655,6 +6664,7 @@ plan_create_index_workers(Oid tableOid, Oid indexOid)
root->query_level = 1;
root->planner_cxt = CurrentMemoryContext;
root->wt_param_id = -1;
root->join_domains = list_make1(makeNode(JoinDomain));
/*
* Build a minimal RTE.