Re: <bug>: erster start

[Karsten Hilbert]

Hello Joshua,

thanks for taking the time to report this issue.

> user comment  : erster start
>
> client version: 1.8.9
...
> Exception:
>
>  type: <class 'psycopg2.errors.SerializationFailure'>
>  value: could not serialize access due to read/write dependencies among 
> transactions
> DETAIL:  Reason code: Canceled on identification as a pivot, during commit 
> attempt.
> TIP:  The transaction might succeed if retried.

What you are seeing happens under very rare circumstances: A
client is started for the very first time against a database
yet devoid of certain configuration values (such as a newly
bootstrapped database) AND the "client version check code" is
running at the "very same time" AND certain lines of
execution coincide precisely.

What is being logged is PostgreSQL helpfully preventing us
from shooting ourselves in the foot -- except that the foot
has long been replaced by a prosthetic limb, which itself is
in the process of being refitted with a new model due to wear
and tear, oh and this is a paintball gun and we are wearing
steel-capped safety boots anyway.

I have reworked the configuration handling for 1.9 so this
report doesn't tell us whether and where this might happen in
that codebase. I have, however, analyzed the circumstances in
the 1.8 branch and have forward-ported removal of that
particular pitfall to 1.9.

So 1.8 will remain wont-fix while 1.9 should fare better.

Best,
Karsten
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GPG  40BE 5B0E C98E 1713 AFA6  5BC0 3BEA AC80 7D4F C89B