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Odd plan shown in src/backend/optimizer/README

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: pgsql-hackers(at)postgresql(dot)org
Subject: Odd plan shown in src/backend/optimizer/README
Date: 2017-01-23 10:11:46
Message-ID: e6cfbaa3-af02-1abc-c25e-8fa5c6bc4e21@lab.ntt.co.jp (view raw, whole thread or download thread mbox)
Thread:
Lists: pgsql-hackers
While working on a bug in postgres_fdw, I found this:

      NestLoop
          -> Seq Scan on SmallTable1 A
          NestLoop
              -> Seq Scan on SmallTable2 B
              NestLoop
                  -> Index Scan using XYIndex on LargeTable C
                        Index Condition: C.X = A.AID and C.Y = B.BID

This seems odd to me; we would not need the bottom-level Nestloop.  
Attached is a small patch for fixing that.  I also adjusted the  
indentation to the last line "Index Condition: ...", to match others in  
the section of Parameterized Paths.

Best regards,
Etsuro Fujita

Attachment: optimizer-readme.patch
Description: text/x-patch (913 bytes)

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