Date: Tue, 4 Jun 2019 15:57:54 +0000
From: Andres Freund <andres@anarazel.de>
To: Amit Khandekar <amitdkhan.pg@gmail.com>
Cc: tushar <tushar.ahuja@enterprisedb.com>,
	Petr Jelinek <petr.jelinek@2ndquadrant.com>,
	Robert Haas <robertmhaas@gmail.com>,
	Craig Ringer <craig@2ndquadrant.com>,
	Petr Jelinek <petr@2ndquadrant.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: Minimal logical decoding on standbys
Message-ID: <20190604155754.ns62je7viqovs2ly@alap3.anarazel.de>
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Hi,

On 2019-05-31 17:31:34 +0530, Amit Khandekar wrote:
> On Fri, 31 May 2019 at 11:08, Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
> >
> > On Thu, 30 May 2019 at 20:13, Andres Freund <andres@anarazel.de> wrote:
> > Yes, it waits until there is a commit record, or (just tried) until a
> > checkpoint command.

That's fine with me.


> Is XLOG_RUNNING_XACTS record essential for the logical decoding to
> build a consistent snapshot ?

Yes.


> Since the restart_lsn is now ReplayRecPtr, there is no
> XLOG_RUNNING_XACTS record, and so the snapshot state is not yet
> SNAPBUILD_CONSISTENT. And so
> DecodingContextFindStartpoint()=>DecodingContextReady() never returns
> true, and hence DecodingContextFindStartpoint() goes in an infinite
> loop, until it gets XLOG_RUNNING_XACTS.

These seem like conflicting statements? Infinite loops don't terminate
until a record is logged?

Greetings,

Andres Freund