Horton

Re: CURRENT OF causes an error when IndexOnlyScan is used

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Yugo Nagata <nagata@sraoss.co.jp>
Cc: pgsql-hackers@postgresql.org
Date: 2018-02-01T02:12:51Z
Lists: pgsql-hackers 
Yugo Nagata <nagata@sraoss.co.jp> writes:
> I'm sorry the patch attached in the previous mail is broken and
> not raises a compile error. I attached the fixed patch.

This patch is almost certainly wrong: you can't assume that the scan-level
state matches the tuple we are currently processing at top level.  Any
sort of delaying action, for instance a sort or materialize node in
between, would break it.

We need to either fix this aspect:

>> IndexOnlyScan returns a virtual tuple that doesn't have system
>> column, so we can not get ctid in the same way of other plans.

or else disallow using IndexOnlyScan when the ctid is needed.

			regards, tom lane

Commits

  1. Fix WHERE CURRENT OF when the referenced cursor uses an index-only scan.