From: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
---|---|
To: | Michael Allman <msa(at)allman(dot)ms> |
Cc: | pgsql-jdbc(at)postgresql(dot)org |
Subject: | Re: prepare() method error |
Date: | 2006-02-12 10:54:30 |
Message-ID: | Pine.OSF.4.61.0602121231150.91568@kosh.hut.fi |
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Thread: | |
Lists: | pgsql-jdbc |
On Sun, 12 Feb 2006, Michael Allman wrote:
> Hi all,
>
> I've been testing the XA implementation and found a bug. The
> PGXAConnection prepare(Xid) method may return a value of XA_OK when it
> should throw an XAException instead. This can lead to an inconsistent TPC
> outcome.
>
> For example, if you attempt to insert a row which violates a uniqueness
> constraint and then prepare the transaction branch, the prepare() method
> returns XA_OK erroneously because the PREPARE TRANSACTION statement
> executes without throwing an exception even though the transaction is not
> prepared.
Good point.
> As a workaround, I've added a query after the PREPARE TRANSACTION query in
> the prepare() method which searches the pg_prepared_xacts table for a row
> with the given gid just "prepared". If it doesn't find the corresponding
> row, it throws an XAException with a suitable error code (I chose
> XA_RBROLLBACK).
>
> It would be cleaner if the driver could determine the success/failure of
> the PREPARE TRANSACTION statement from the query itself. For instance,
> have the executeUpdate("PREPARE TRANSACTION " ....) return normally if and
> only if it actually prepares a transaction. If it doesn't prepare, throw
> a meaningful SQLException.
We can check the command status string. PREPARE TRANSACTION should
return "PREPARE TRANSACTION" command status on success and "ROLLBACK" on
failure.
- Heikki
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