MIME-Version: 1.0
From: Josh Kupershmidt <schmiddy@gmail.com>
Date: Thu, 8 Nov 2012 19:56:00 -0700
Message-ID: 
 <CAK3UJRELGc4v_aoRstG8kY0JfCrt4xNUeW=uxtnwPSZ4zV5nMQ@mail.gmail.com>
Subject: streaming replication confusion
To: pgsql-docs <pgsql-docs@postgresql.org>
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I think there is at least[4] one confusing documentation leftover from
the 9.0 days at:
  http://www.postgresql.org/docs/devel/static/warm-standby.html

First, we claim:

| Streaming replication is asynchronous, so there is still a small delay
| between committing a transaction in the primary and for the changes
| to become visible in the standby.

This unqualified statement, which has remained the same since 9.0,
suggests synchronous replication is not possible using streaming
replication. Further down we are closer to the truth:

| PostgreSQL streaming replication is asynchronous by default.

Proposed fix for this gripe attached. I'd be pleased to see this
particular doc patch backpatched to 9.2 and 9.1, given that the
replication docs are both important and fairly confusing.

The Streaming Replication wiki page[1] contains similar out-of-date
claims[2]; I can fix some of the egregious errors myself, though help
is welcome. The "Synchronous Replication" wiki page[3] is in even
worse shape, containing mostly info about a patch different than what
was committed... and it's currently the first Google search result for
"postgresql synchronous replication" :-(

Josh

[1] http://wiki.postgresql.org/wiki/Streaming_Replication
[2] such as "Currently SR supports only asynchronous log-shipping", or
already-released functionality described under the "Future release
section".
[3] http://wiki.postgresql.org/wiki/Synchronous_replication
[4] I have a larger gripe about the way this entire page is laid out,
with streaming rep. info bolted onto a page which is still named and
was intended to be about warm standby, but I'll try to make a separate
thread about that.

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