Re: pglogical most basic setup for logical replication

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От Craig Ringer
Тема Re: pglogical most basic setup for logical replication
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Msg-id CAMsr+YE9oT8EGSzWgny+H1aHT0D3dwqXfAoXU7Y3wbK+-5rV-Q@mail.gmail.com
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Ответ на Re: pglogical most basic setup for logical replication  (Sebastien Diemer <sebastien.diemer@polyconseil.fr>)
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On 26 January 2016 at 19:18, Sebastien Diemer <sebastien.diemer@polyconseil.fr> wrote:
It sounds like you must be running on PostgreSQL 9.4.
Indeed I am on PostgreSQL 9.4, I omitted this important point. 


I'll update the docs to mention the extra step on 9.4.
 
You'll need to drop the subscriber database and re-create it. Use a new node name.
Seems to work but I still do not really understand what was wrong in the first place though.
Thanks for your help Craig !

It's because internally pglogical relies on pg_dump and pg_restore to set up the initial database state. If it fails partway through a pg_restore there's no sensible way to undo those changes, especially since we have to do it in a number of steps to achieve a partial restore.

A cleaner handling of this really requires the ability to use pg_dump's functionality over a normal protocol connection from SQL, or at least as a library.

The error should probably get a HINT to say that an incomplete restore means the DB may have to be dropped and recreated.

It's all a bit messy, since we support multiple upstreams and support writes directly into the downstream. So you actually can't always just drop the downstream. A really good solution to this needs the ability to compare various objects (type definitions, tables, etc), the ability to extract just a required subset of dependencies from a database and other complexities. 

--
 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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