On Wed, Feb 19, 2025 at 11:15 PM Robert Treat wrote:
> On Wed, Feb 19, 2025 at 10:07 PM Bruce Momjian wrote:
>> On Sat, Oct 12, 2024 at 07:01:31AM +0200, Laurenz Albe wrote:
>> > 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.
>>
>
> The attached patch expands on Paul's original patch, further consolidating
> around the terms "streaming physical replication" and "streaming logical
> replication" in places where it makes sense. I would note that there are
> places where "streaming replication" makes sense (when it applies to both
> types) and potentially when "physical replication" might make sense when we
> could be talking about either streaming or wal shipping, so I don't think we
> can completely eliminate that, but hopefully this improves what we have.
>
>>
>> I don't think our current setup is sustainable so I think it does need
>> to be cleaned up. Also, physical/logical replication slots also needs
>> help, I think.
>>
>
> I took a look through some of the replication slot stuff and ISTM that it
> basically gets the streaming logical/physical replication distinctions
> correct, and I *think*
> it gets the slot distinctions correct as well, but to the degree there might
> be some issue there, I think it could be addressed separately.
>
Hey Bruce,
Your recent commit on this topic [1] reminded me of the patch from
earlier this year meant to address some other areas where we are
blurry about using streaming vs physical vs logical replication. I
think (I might possibly still be jet lagged) I have updated the
previous version of that patch against HEAD, attached, and bumping it
up for review.
[1]
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=a5b69e30731fb623715ecf4c8073c0f2dee41678;hp=acbc9beaaed6ee88416e1dcef5df77fd5baba0be)
Robert Treat
https://xzilla.net
v3-0001-Clarify-usage-of-the-term-streaming-replication.patch
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