Horton

Re: pg_receivewal starting position

Ronan Dunklau <ronan.dunklau@aiven.io>

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From: Ronan Dunklau <ronan.dunklau@aiven.io>
To: Michael Paquier <michael@paquier.xyz>
Cc: pgsql-hackers@lists.postgresql.org, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>
Date: 2021-10-25T07:50:01Z
Lists: pgsql-hackers 
Le lundi 25 octobre 2021, 09:40:10 CEST Michael Paquier a écrit :
> On Mon, Oct 25, 2021 at 09:15:32AM +0200, Ronan Dunklau wrote:
> > Does it make sense though ? The NULL slot_name case handling is pretty
> > straight forward has it will be handled by string formatting, but in the
> > case of a null restart_lsn, we have no way of knowing if the command was
> > issued at all.
> 
> If I am following your point, I don't think that it matters much here,
> and it seems useful to me to be able to pass NULL for both of them, so
> as one can check if the slot exists or not with an API designed this
> way.

You're right, but I'm afraid we would have to check the server version twice 
in any case different from the basic pg_receivewal on (once in the function 
itself, and one before calling it if we want a meaningful result). Maybe we 
should move the version check outside the GetSlotInformation function to avoid 
this, and let it fail with a syntax error when the server doesn't support it ?

-- 
Ronan Dunklau

Commits

  1. Add TAP test for pg_receivewal with timeline switch

  2. Speed up TAP tests of pg_receivewal

  3. Allow pg_receivewal to stream from a slot's restart LSN

  4. Add replication command READ_REPLICATION_SLOT

  5. doc: Describe calculation method of streaming start for pg_receivewal

  6. Add PostgresNode::command_fails_like()