From: Tom Lane <tgl@sss.pgh.pa.us>
To: Yugo Nagata <nagata@sraoss.co.jp>
cc: pgsql-hackers@postgresql.org
Subject: Re: CURRENT OF causes an error when IndexOnlyScan is used
In-reply-to: <20180201014444.f78358df.nagata@sraoss.co.jp>
References: <20180201013349.937dfc5f.nagata@sraoss.co.jp>
 <20180201014444.f78358df.nagata@sraoss.co.jp>
Comments: In-reply-to Yugo Nagata <nagata@sraoss.co.jp>
	message dated "Thu, 01 Feb 2018 01:44:44 +0900"
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Content-ID: <22957.1517451171.1@sss.pgh.pa.us>
Date: Wed, 31 Jan 2018 21:12:51 -0500
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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