Re: Concurrent connections in psql

What are people's opinions on this patch?  (It is at the URL below.)

I like the capability, and am impressed it allowed testing that found
some concurrency bugs in our server, but it is a large patch to psql.

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Gregory Stark wrote:
> 
> I mentioned this a while back, now that 8.2 is out perhaps others will be more
> interested in new code.
> 
> Currently Postgres regression tests only test functionality within a single
> session. There are no regression tests that test the transaction semantics or
> locking behaviour across multiple transactions.
> 
> I modified psql to allow you to open multiple connections and switch between
> them with a sort of csh job control style interface. It actually works out
> pretty well. It's fairly easy to write regression tests for basic 2-client or
> 3-client cases.
> 
> The actual user interface may need some discussion though. I didn't want to
> play the name game so I just prefixed all my commands with "c" and figured we
> can always rename them later.
> 
> And experience with actually writing the tests shows that the explicit \cwait
> command which was needed to eliminate (in practice if not in theory) race
> conditions in regression tests turns out to be more flexibility than
> necessary. Since you end up having to insert one in precisely predictable
> locations -- namely after every asynchronous command and after every
> connection switch -- perhaps it would be simpler to just have a "\pset cwait"
> command that automatically introduces timeouts in precisely those places.
> 
> A brief explanation including an example regression test (the SAVEPOINT
> locking bug discovered recently) and the patch here:
> 
>   http://community.enterprisedb.com/concurrent/index.html
> 
> -- 
>   Gregory Stark
>   EnterpriseDB          http://www.enterprisedb.com
> 
> 
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