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From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Paul A Jungwirth <pj@illuminatedcomputing.com>
To: pgsql-docs@lists.postgresql.org
Subject: Re: Streaming Replication vs Logical
Date: Sat, 12 Oct 2024 07:01:31 +0200
Message-ID: <2c392993640661b817c5c779f6aaf44c103510bf.camel@cybertec.at> (raw)
In-Reply-To: <CA+renyULt3VBS1cRFKUfT2=5dr61xBOZdAZ-CqX3XLGXqY-aTQ@mail.gmail.com>
References: <CA+renyULt3VBS1cRFKUfT2=5dr61xBOZdAZ-CqX3XLGXqY-aTQ@mail.gmail.com>

On Fri, 2024-10-11 at 15:53 -0700, Paul A Jungwirth wrote:
> Our docs seem to contrast "streaming replication" to logical, but
> these are not really opposites. Sometimes when they say "streaming"
> they mean "physical".
> 
> Probably this is historical: at first physical replication was the
> only kind of streaming we had.
> 
> Personally this has caused me a lot of confusion. For example,
> recently when I read "Synchronous replication (see Section 26.2.8) is
> only supported on replication slots used over the streaming
> replication interface," I took it to mean synchronous replication only
> worked for physical replication, not logical.

What you are saying makes a lot of sense, and improving some of this
is a good thing.

Our current trminology is a mess.  There are some places in the documentation
that speak of physical vs. logical replication, while most places use the
term "streaming replication" for physical replication.  I myself consequently
speak of "streaming replication" vs. "logical replication", even though both
stream data.  The protocol section of the documentation describes the
"streaming replication protocol" and the "logical streaming replication protocol".

This is confusing, and I am also sometimes confused in the way you described
above.

I think the mess is too well established to be really cleaned up.  But adding
some clarity is a good thing, so +1.

Yours,
Laurenz Albe

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