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Fix nested PlaceHolderVar expressions that appear only in targetlists.

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A PlaceHolderVar's expression might contain another, lower-level
PlaceHolderVar.  If the outer PlaceHolderVar is used, the inner one
certainly will be also, and so we have to make sure that both of them get
into the placeholder_list with correct ph_may_need values during the
initial pre-scan of the query (before deconstruct_jointree starts).
We did this correctly for PlaceHolderVars appearing in the query quals,
but overlooked the issue for those appearing in the top-level targetlist;
with the result that nested placeholders referenced only in the targetlist
did not work correctly, as illustrated in bug #6154.

While at it, add some error checking to find_placeholder_info to ensure
that we don't try to create new placeholders after it's too late to do so;
they have to all be created before deconstruct_jointree starts.

Back-patch to 8.4 where the PlaceHolderVar mechanism was introduced.
This commit is contained in:
Tom Lane
2011-08-09 00:48:51 -04:00
parent d82a9d2a60
commit 77ba232564
8 changed files with 163 additions and 40 deletions
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2
src/backend/optimizer/path/costsize.c
View File

@ -3491,7 +3491,7 @@ set_rel_width(PlannerInfo *root, RelOptInfo *rel)
else if (IsA(node, PlaceHolderVar))
{
PlaceHolderVar *phv = (PlaceHolderVar *) node;
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
PlaceHolderInfo *phinfo = find_placeholder_info(root, phv, false);
tuple_width += phinfo->ph_width;
}

2
src/backend/optimizer/path/equivclass.c
View File

@ -850,7 +850,7 @@ generate_base_implied_equalities_no_const(PlannerInfo *root,
PVC_RECURSE_AGGREGATES,
PVC_INCLUDE_PLACEHOLDERS);
add_vars_to_targetlist(root, vars, ec->ec_relids);
add_vars_to_targetlist(root, vars, ec->ec_relids, false);
list_free(vars);
}
}