On 02/13/2012 11:00 AM, Tom Lane wrote:
Robert Haas<robertmh...@gmail.com>  writes:
On Sat, Feb 11, 2012 at 11:11 AM, Andrew Dunstan
<aduns...@postgresql.org>  wrote:
Do we actually need to bother with these cases?
In flatten_join_alias_vars_mutator(), we've got a RangeTblEntry to
work with.  I think the column names are to be found in the alias
and/or eref attributes of the RangeTblEntry.
The eref names are the ones to use.  alias just records the original AS
clause (if any) attached to the RTE, which is mostly useful only for
reverse-listing the query.

In adjust_appendrel_attrs_mutator(), we have a list, translated_vars,
whose order matches the column order of the parent rel.  If we had the
parent's RangeTblEntry, we could probably precede as in the previous
case.  But the AppendRelInfo only contains the index of the RT.  Maybe
we can figure out a way to use rt_fetch to get the RangeTblEntry
itself, but that requires a pointer to the range table itself, which
we haven't got.
This is surely fixable by passing a bit more information down.  If you
(Andrew) have something that covers everything but this issue, pass it
over and I'll take a whack at it.

What I have fixes one of the three cases I have identified that appear to need fixing, the one that caused the json tests to crash with your original partial patch. See <https://bitbucket.org/adunstan/pgdevel/changesets/tip/rowexprs>. I won't have time to return to this for a few days. The two remaining cases should be fairly independent I think. If you don't get to this before then I'll look at the flatten_join_alias_vars_mutator case again and try to fix it based on the above, and then give you what I've got.



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