On 5/28/2010 7:19 PM, Bruce Momjian wrote:
Jan Wieck wrote:
>> Reading the entire WAL just to find all COMMIT records, then go back to
>> the origin database to get the actual replication log you're looking for
>> is simpler and more efficient? I don't think so.
>
> Agreed, but I think I've not explained myself well enough.
>
> I proposed two completely separate ideas; the first one was this:
>
> If you must get commit order, get it from WAL on *origin*, using exact
> same code that current WALSender provides, plus some logic to read
> through the WAL records and extract commit/aborts. That seems much
> simpler than the proposal you outlined and as SR shows, its low latency
> as well since commits write to WAL. No need to generate event ticks
> either, just use XLogRecPtrs as WALSender already does.
>
> I see no problem with integrating that into core, technically or
> philosophically.
>
Which means that if I want to allow a consumer of that commit order data
to go offline for three days or so to replicate the 5 requested, low
volume tables, the origin needs to hang on to the entire WAL log from
all 100 other high volume tables?
I suggest writing an external tool that strips out what you need that
can be run at any time, rather than creating a new data format and
overhead for this usecase.
Stripping it out from what?
Jan
--
Anyone who trades liberty for security deserves neither
liberty nor security. -- Benjamin Franklin
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