[Bucardo-general] Burcardo.pm 4.4.8 crashed on small systems - patch attached
Armin B. Resch
reschab at gmail.com
Sat Dec 15 04:21:11 UTC 2012
I agree - making chunk size configurable would be best.
-ar
On 12/14/2012 03:37 PM, Rosser Schwarz wrote:
> I can't speak to your proposed algorithmic changes, but I do think
> chunk size should maybe be configurable, to help deal with low-memory
> environments like the OP's, and to allow DBAs to set larger chunk
> sizes, when they've also set max_stack_depth and the relevant ulimits
> accordingly.
>
>
> On Fri, Dec 14, 2012 at 12:41 PM, Armin Resch <armin at reschab.net
> <mailto:armin at reschab.net>> wrote:
>
> Bucardoans,
>
> we had a situation in which our memory-constrained device would
> pick bucardo_ctl or a postgres backend as a candidate to be killed
> when more than 3,000 deltas would have to be copied to a slave in
> one transaction. I attached a patch to correct the situation and
> was wondering whether it can be considered to be applied upstream
> - at least for B4; it applies to the PUSHDELTA section. In
> addition to the smaller chunk size (which admittedly might not be
> ideal for larger systems), it contains the following changes:
>
> 1 - Allow tables to be replicated which contain unique keys where
> one or more columns are NULL
> 2 - performance improvement by refactoring processing of the delta
> record set
>
> With regard to (1), we found out that Bucardo would not replicate
> unique keys containing NULLs because the Postgres syntax does not
> produce output for the following WHERE clause:
>
> WHERE (col1,col2,col3,col4) IN
> (('A','B',NULL,'D'),('A',NULL,'C',NULL))
>
> The algorithm would split those COPY operations into two separate
> queries as such:
>
> A) <blah> WHERE (col1,col2,col4) IN (('A','B','D')) AND col3 IS NULL
> B) <blah> WHERE (col1,col3) IN (('A','C') AND col2 IS NULL AND
> col4 IS NULL
>
> Best,
> -ar
>
>
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>
>
> --
> :wq
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