[Dbix-class] Strange statistically significant failure for DBIC with Sybase

[Phillip Moore]

I'm working with a very large, and very old software product, and trying to
convert it's ancient Sybase tables to modern, normalized forms with a DBIC
API to access it.   Things have been going well, until I started
parallelizing the data conversion, and hitting the database a little hard
(up to 16 processes at a time -- hardly "huge" by modern standards).

I'm starting to see a problem where about 2% of the DBIC objects I create
come back with a primary key (which is a Sybase identity column) whose
value has been incremented one too many times.   Then, when I create
related objects and assign that identity value as a foreign key, the
relationships are essentially corrupted.  Things get associated with the
wrong object.

The 2% failure rate is reproducible, but when I convert the entire legacy
database to the new schema, it's a different, seemingly random subset of
objects that get returned this way.  I figured out what was happening by
noticing the off by one error, and then sanity checking the metadata for
id-1 and finding THAT to be correct.

I'm using DBIC 0.08250 with DBD-Sybase 1.14 (both are a tad out of date;
I've requested upgrades, which sadly I no longer control) against a Sybase
ASE 12.5.4 server.

I am working on getting more in depth debugging information, and I am well
aware that this problem report is lacking in such details, but in the
meantime do these symptoms sound familiar to anyone at all?
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