Re: Odd system-column handling in postgres_fdw join pushdown patch

On Wed, Apr 13, 2016 at 11:21 PM, Etsuro Fujita
<fujita.etsuro@lab.ntt.co.jp> wrote:
>>> 2. When a join is pushed down, deparse system columns using something
>>> like "CASE WHEN r1.* IS NOT NULL THEN 0 END", except for the table OID
>>> column, which gets deparsed with the table OID in place of 0.  This
>>> delivers the correct behavior in the presence of outer joins.
>> I think that that would cause useless data transfer for such culumns.
>> Why not set values locally for such columns?

Because that doesn't work properly when there are outer joins
involved.  I see no other way of doing that correctly that's anywhere
near as simple as this.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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