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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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8
src/backend/optimizer/util/placeholder.c
View File

@@ -412,14 +412,14 @@ add_placeholders_to_base_rels(PlannerInfo *root)
PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
Relids eval_at = phinfo->ph_eval_at;
if (bms_membership(eval_at) == BMS_SINGLETON)
if (bms_membership(eval_at) == BMS_SINGLETON &&
bms_nonempty_difference(phinfo->ph_needed, eval_at))
{
int varno = bms_singleton_member(eval_at);
RelOptInfo *rel = find_base_rel(root, varno);
if (bms_nonempty_difference(phinfo->ph_needed, rel->relids))
rel->reltargetlist = lappend(rel->reltargetlist,
copyObject(phinfo->ph_var));
rel->reltargetlist = lappend(rel->reltargetlist,
copyObject(phinfo->ph_var));
}
}
}