[Bucardo-general] Burcardo.pm 4.4.8 crashed on small systems - patch attached

Rosser Schwarz rosser.schwarz at gmail.com
Fri Dec 14 21:37:48 UTC 2012

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> 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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