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Fix up planner infrastructure to support LATERAL properly.

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This patch takes care of a number of problems having to do with failure
to choose valid join orders and incorrect handling of lateral references
pulled up from subqueries.  Notable changes:

* Add a LateralJoinInfo data structure similar to SpecialJoinInfo, to
represent join ordering constraints created by lateral references.
(I first considered extending the SpecialJoinInfo structure, but the
semantics are different enough that a separate data structure seems
better.)  Extend join_is_legal() and related functions to prevent trying
to form unworkable joins, and to ensure that we will consider joins that
satisfy lateral references even if the joins would be clauseless.

* Fill in the infrastructure needed for the last few types of relation scan
paths to support parameterization.  We'd have wanted this eventually
anyway, but it is necessary now because a relation that gets pulled up out
of a UNION ALL subquery may acquire a reltargetlist containing lateral
references, meaning that its paths *have* to be parameterized whether or
not we have any code that can push join quals down into the scan.

* Compute data about lateral references early in query_planner(), and save
in RelOptInfo nodes, to avoid repetitive calculations later.

* Assorted corner-case bug fixes.

There's probably still some bugs left, but this is a lot closer to being
real than it was before.
This commit is contained in:
Tom Lane
2012-08-26 22:48:55 -04:00
parent de87d47044
commit 9ff79b9d4e
30 changed files with 818 additions and 183 deletions
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30
src/backend/optimizer/path/joinpath.c
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@ -149,28 +149,20 @@ add_paths_to_joinrel(PlannerInfo *root,
/*
* However, when a LATERAL subquery is involved, we have to be a bit
* laxer, because there may simply not be any paths for the joinrel that
* aren't parameterized by whatever the subquery is parameterized by.
* Hence, add to param_source_rels anything that is in the minimum
* parameterization of either input (and not in the other input).
*
* XXX need a more principled way of determining minimum parameterization.
* laxer, because there will simply not be any paths for the joinrel that
* aren't parameterized by whatever the subquery is parameterized by,
* unless its parameterization is resolved within the joinrel. Hence, add
* to param_source_rels anything that is laterally referenced in either
* input and is not in the join already.
*/
if (outerrel->cheapest_total_path == NULL)
foreach(lc, root->lateral_info_list)
{
Path *cheapest = (Path *) linitial(outerrel->cheapest_parameterized_paths);
LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(lc);
param_source_rels = bms_join(param_source_rels,
bms_difference(PATH_REQ_OUTER(cheapest),
innerrel->relids));
}
if (innerrel->cheapest_total_path == NULL)
{
Path *cheapest = (Path *) linitial(innerrel->cheapest_parameterized_paths);
param_source_rels = bms_join(param_source_rels,
bms_difference(PATH_REQ_OUTER(cheapest),
outerrel->relids));
if (bms_is_member(ljinfo->lateral_rhs, joinrel->relids))
param_source_rels = bms_join(param_source_rels,
bms_difference(ljinfo->lateral_lhs,
joinrel->relids));
}
/*