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A connection is being checked twice for being dead (by calling FConnections.Rollback) . Both when it is Acquired and when it is being returned to
the pool (see TConnectionPool.ReturnToPool and TConnectionPool.Acquire ).

Calling rollback is expensive.

I believe that TConnectionPool.ReturnToPool call is redundant. And removing it will not change the way applications actually work.


Thanks,
Yoni

Hello Yoni,

did you check that removing the call actually improves performance in your setup? Just out of curiosity: Which database / zeos driver do you use?

Best regards,

Jan

Hi,

Sure. I removed the code and it does improve the performance. I'm using the PostgreSQL driver (connecting to server v13.2).

Doing a rollback is very expensive, as you have a full roundtrip to the server .


As aside note, there is also a bug that can lead to connection leakage when doing a rollback and the connection is set to AutoCommit, PostgreSQL throws an exception stating that an AutoCommit connection cannot be rolledback, then TConnectionPool.ReturnToPool marks this connection as unusable and obtains a new one while not closing or releasing the first