Date: Thu, 30 May 2019 07:17:23 -0700
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
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Hi,

On 2019-05-30 19:46:26 +0530, Amit Khandekar wrote:
> @@ -1042,7 +1042,8 @@ ReplicationSlotReserveWal(void)
>  if (!RecoveryInProgress() && SlotIsLogical(slot))
>  {
>     ....
>  }
>  else
>  {
> -   restart_lsn = GetRedoRecPtr();
> +   restart_lsn = SlotIsLogical(slot) ?
> +                        GetXLogReplayRecPtr(&ThisTimeLineID) : GetRedoRecPtr();
> 
> But then when I do pg_create_logical_replication_slot(), it hangs in
> DecodingContextFindStartpoint(), waiting to find new records
> (XLogReadRecord).

But just till the primary has logged the necessary WAL records? If you
just do CHECKPOINT; or such on the primary, it should succeed quickly?

Greetings,

Andres Freund