Replication in main PostgreSQL codebase

[Matt Browne]

Hello all!

I apologise in advance if any of my questions are in a FAQ somewhere - I
haven't seen them...

Does anyone know when (if ever) replication support will be added to the
main PostgreSQL codebase? Is there any chance it'll be included in the
upcoming 7.5 release?

I've taken a look at the replication solutions already available, including
the sterling effort made on Slony-I, but we're really looking for
integrated, base-level support rather than an add-in.

Cheers!


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[Christopher Browne]

Post by Matt Browne
I apologise in advance if any of my questions are in a FAQ somewhere - I
haven't seen them...
Does anyone know when (if ever) replication support will be added to the
main PostgreSQL codebase? Is there any chance it'll be included in the
upcoming 7.5 release?

Not much of a chance.

Post by Matt Browne
I've taken a look at the replication solutions already available,
including the sterling effort made on Slony-I, but we're really
looking for integrated, base-level support rather than an add-in.

The problem is that "replication" doesn't tend to mean one thing, but
people rather have different ideas of what it means.

Jan Wieck puts it fairly nicely:

"The number of different replication solutions available supports
the theory that ``one size fits all'' is not true when it comes to
database replication."

[Matt Browne]

Post by Christopher Browne

Post by Matt Browne
I've taken a look at the replication solutions already available,
including the sterling effort made on Slony-I, but we're really
looking for integrated, base-level support rather than an add-in.

The problem is that "replication" doesn't tend to mean one
thing, but people rather have different ideas of what it means.

I don't necessarily agree with that. It's true that one size hardly ever
fits all, especially when it comes to implementation, but I think people
have a certain replication feature set in mind when they come across a DBMS
that purports to be enterprise-class...

... Just like what's been listed in the 'Urgent' section of the TODO list
since (I think) 7.2, in fact. (Except perhaps the more complex features like
multi-master replication.)

I didn't post my original message to the pgsql-hackers list because I wanted
to respect the ominous warning about trying other lists first.

Not to discount your comments, Christopher, but is there anyone on this list
who could give me an official and authoritative line on the inclusion of
in-built replication functionality?

Thanks again!


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[Marc G. Fournier]

Post by Matt Browne

Post by Christopher Browne

Post by Matt Browne
I've taken a look at the replication solutions already available,
including the sterling effort made on Slony-I, but we're really
looking for integrated, base-level support rather than an add-in.

The problem is that "replication" doesn't tend to mean one
thing, but people rather have different ideas of what it means.

I don't necessarily agree with that. It's true that one size hardly ever
fits all, especially when it comes to implementation, but I think people
have a certain replication feature set in mind when they come across a DBMS
that purports to be enterprise-class...
... Just like what's been listed in the 'Urgent' section of the TODO list
since (I think) 7.2, in fact. (Except perhaps the more complex features like
multi-master replication.)
I didn't post my original message to the pgsql-hackers list because I wanted
to respect the ominous warning about trying other lists first.
Not to discount your comments, Christopher, but is there anyone on this list
who could give me an official and authoritative line on the inclusion of
in-built replication functionality?

Christopher is correct ... if there was such a thing as an 'end all, be
all' replication solution, there wouldn't be a half a dozen different ones
out there ...

It would be unwise for *anyone* to state "never" as far as inclusion of
built-in replication, but since the general consensus is that there is no
such thing as the 'all-encompassing solution' for this, the chances of one
ever coming about that would be of a scope that would be acceptable to be
built-in is next to zero ...

----
Marc G. Fournier Hub.Org Networking Services (http://www.hub.org)
Email: ***@hub.org Yahoo!: yscrappy ICQ: 7615664

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[Bruce Momjian]

Post by Marc G. Fournier
Christopher is correct ... if there was such a thing as an 'end all, be
all' replication solution, there wouldn't be a half a dozen different ones
out there ...
It would be unwise for *anyone* to state "never" as far as inclusion of
built-in replication, but since the general consensus is that there is no
such thing as the 'all-encompassing solution' for this, the chances of one
ever coming about that would be of a scope that would be acceptable to be
built-in is next to zero ...

OK, I reworded the replication TODO section and moved it under
Administration:

* Improve replication solutions
o Automatic failover
o Load balancing
o Master/slave replication
o Multi-master replication
o Partition data across servers
o Queries across databases or servers (two-phase commit)
o Allow replication over unreliable or non-persistent links
--
Bruce Momjian | http://candle.pha.pa.us
***@candle.pha.pa.us | [phone]
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073

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[Christopher Petrilli]

On Tue, 6 Jul 2004 17:07:33 -0300 (ADT), Marc G. Fournier

Post by Marc G. Fournier
It would be unwise for *anyone* to state "never" as far as inclusion of
built-in replication, but since the general consensus is that there is no
such thing as the 'all-encompassing solution' for this, the chances of one
ever coming about that would be of a scope that would be acceptable to be
built-in is next to zero ...

I think what I run into is that while most of us would agree that the
"one size fits all" argument is useless from a technical perspective,
it's not the technical people that are usually the ones involved here.
From a "marketing" perspective, it would be useful if PostgreSQL
included at least a single master, single slave replication model that
was easily enabled and set up. There is a subclass of the problem that
is common to most situations, which is the ability to have a "live"
backup. Perhaps the 'dbmirror' component in the 'contrib' directory
is enough, and it simply needs to be highlighted. It does meet some
subset of the needs out there.

Sadly, a lot of problems are simply marketing perceptions :/

Chris

[Peter Eisentraut]

Post by Marc G. Fournier
Christopher is correct ... if there was such a thing as an 'end all,
be all' replication solution, there wouldn't be a half a dozen
different ones out there ...

Which ones are you thinking of in your count? I don't get anywhere near
half a dozen.


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[Marc G. Fournier]

Post by Peter Eisentraut

Post by Marc G. Fournier
Christopher is correct ... if there was such a thing as an 'end all,
be all' replication solution, there wouldn't be a half a dozen
different ones out there ...

Which ones are you thinking of in your count? I don't get anywhere near
half a dozen.

erserver, slony, dbmirror are off the top of my head for OSS ones ... then
Command Prompt has their replication solution, so that's four ... wasn't
there one out of russia? I can't recall the name of it though :(
apparently someone is still working on pgreplication ...


----
Marc G. Fournier Hub.Org Networking Services (http://www.hub.org)
Email: ***@hub.org Yahoo!: yscrappy ICQ: 7615664

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[Bruce Momjian]

Post by Marc G. Fournier

Post by Peter Eisentraut

Post by Marc G. Fournier
Christopher is correct ... if there was such a thing as an 'end all,
be all' replication solution, there wouldn't be a half a dozen
different ones out there ...

Which ones are you thinking of in your count? I don't get anywhere near
half a dozen.

erserver, slony, dbmirror are off the top of my head for OSS ones ... then
Command Prompt has their replication solution, so that's four ... wasn't
there one out of russia? I can't recall the name of it though :(
apparently someone is still working on pgreplication ...

And pgcluster, which does multi-master.

[Peter Eisentraut]

Post by Christopher Browne
"The number of different replication solutions available supports
the theory that ``one size fits all'' is not true when it comes to
database replication."

The fact that all but one or two replication solutions out there are
pretty much dead supports the theory that "one size fits most" is true.

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