| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Daniel Farina <daniel(at)heroku(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Subject: | Re: [PATCH 10/16] Introduce the concept that wal has a 'origin' node |
| Date: | 2012-06-19 14:30:59 |
| Message-ID: | 12098.1340116259@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> On Tuesday, June 19, 2012 04:17:01 PM Tom Lane wrote:
>> ... (If you are thinking
>> of something sufficiently high-level that merging could possibly work,
>> then it's not WAL, and we shouldn't be trying to make the WAL
>> representation cater for it.)
> The idea is that if youre replaying changes on node A originating from node B
> you set the origin to *B* in the wal records that are generated during that.
> So when B, in a bidirectional setup, replays the changes that A has made it
> can simply ignore all changes which originated on itself.
This is most certainly not possible at the level of WAL. As I said
above, we shouldn't be trying to shoehorn high level logical-replication
commands into WAL streams. No good can come of confusing those concepts.
regards, tom lane
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