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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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21
src/backend/optimizer/plan/analyzejoins.c
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@ -298,6 +298,7 @@ remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)
List *joininfos;
Index rti;
ListCell *l;
ListCell *nextl;
/*
* Mark the rel as "dead" to show it is no longer part of the join tree.
@ -350,6 +351,26 @@ remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)
sjinfo->syn_righthand = bms_del_member(sjinfo->syn_righthand, relid);
}
/*
* Likewise remove references from LateralJoinInfo data structures.
*
* If we are deleting a LATERAL subquery, we can forget its
* LateralJoinInfo altogether. Otherwise, make sure the target is not
* included in any lateral_lhs set. (It probably can't be, since that
* should have precluded deciding to remove it; but let's cope anyway.)
*/
for (l = list_head(root->lateral_info_list); l != NULL; l = nextl)
{
LateralJoinInfo *ljinfo = (LateralJoinInfo *) lfirst(l);
nextl = lnext(l);
if (ljinfo->lateral_rhs == relid)
root->lateral_info_list = list_delete_ptr(root->lateral_info_list,
ljinfo);
else
ljinfo->lateral_lhs = bms_del_member(ljinfo->lateral_lhs, relid);
}
/*
* Likewise remove references from PlaceHolderVar data structures.
*