[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.

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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