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Why we can't share PreparedStatement cache across connections

Maulin Vasavada
Ranch Hand

Joined: Nov 04, 2001
Posts: 1871
Hi all,

I was wondering what could be the reason that PreparedStatement cache is for each Connection object individually? Why we can't share cached PreparedStatement across multiple connections?

If we can't share PreparedStatement cache across connections then this is the problem I see,
Consider we have Connection pool and for a Request1 the connection caches the PreparedStatement1 . Now, if there is Request2 and for the same PreparedStatement1 it ends up getting another Connection from the pool then the cache that exist in the other connection for this statement is not useful.

Here if we had the shared of PreparedStatement across connections then we could have used the same cached PreparedStatement for both the requests.

Please give your views/understanding on this.

Regards,
Maulin
[ September 20, 2005: Message edited by: Maulin Vasavada ]
Rajesh Agarwal
Ranch Hand

Joined: Aug 01, 2005
Posts: 79
Maulin,

I understand that for 1 PreparedStatement, all the DB resources like
execution plan and execution path and such things are dedicated to only that connection and is not available to other connection.
David O'Meara
Rancher

Joined: Mar 06, 2001
Posts: 13459

Yep, if the database and driver both support PreparedStatements, it gets cached on the database and not by the Driver.
Maulin Vasavada
Ranch Hand

Joined: Nov 04, 2001
Posts: 1871
Okay..

I will have to catch some DBA to understand "why so".

Thank you guys for the responses.

Regards
Maulin
Maximilian Xavier Stocker
Ranch Hand

Joined: Sep 20, 2005
Posts: 381
Maulin,

I don't think you need a DBA. All there is to know is that caching of Statements and PreparedStatements is handled differently by different DB vendors and JDBC drivers. In short there is no clear-cut answer to this.

Largely though I think you should just be happy with whatever caching exists because that is what the RDBMS and driver handle for you. The creators of that software spend most of their time configuring their applications to provide optimal levels of performance in terms of cacheing (statements and results) vs. memory usage and that sort of thing.
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Why we can't share PreparedStatement cache across connections