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From Dag Wanvik <dag.wan...@oracle.com>
Subject Re: concurrent execution of Statement's .addBatch() and .executeBatch()
Date Mon, 10 Dec 2012 19:52:50 GMT

On 07.12.2012 16:53, Pavel Bortnovskiy wrote:
> Thank you, Knut.
> It has been my assumption that creation of PreparedStatement is expensive. Thus I create
cached Prepared Statements (such as INSERT, UPDATE, DELETE, SELECT COUNT(*) FROM <table>)
and then use them. Would it be an improvement in my design to create multiple PreparedStatements
for those (assuring proper addition of objects and execution)? Would you still recommend caching
and reusing them or creating them anew?
Please also note that as long as the statements are textually the same,
i.e. arguments are given dynamically as "?" , Derby is able to use its
internal cache to avoid SQL compilation for more than the first thread,
even if each of the thread has a created a separate PreparedStatement in
its own connection. Cf.


> For instance, if I have 3,000 records to insert, I could split them into 6x500 batches,
create 6 PreparedStatements and have each of them execute their corresponding batches in parallel.
> Thank you,
> Pavel.
> -----Original Message-----
> From: Knut Anders Hatlen [mailto:knut.hatlen@oracle.com]
> Sent: Friday, December 07, 2012 7:01 AM
> To: Derby Discussion
> Subject: Re: concurrent execution of Statement's .addBatch() and .executeBatch()
> Pavel Bortnovskiy <pbortnovskiy@jefferies.com> writes:
>> Hello:
>> Is it safe to call .addBatch() and .executeBatch() methods from
>> multiple threads on the same PreparedStatement?
>> Simple example: batching and executing a large number of the same
>> statements (with the same PreparedStatement) by using ExecutorService.
> Hi Pavel,
> Both addBatch() and executeBatch() do their work in a block synchronized on the connection,
so in theory it should work to have many threads adding batches to the same PreparedStatement.
I don't think it has been heavily tested, though.
> And if the threads set any parameters on the PreparedStatement, your application needs
to synchronize the threads manually. For example, if two threads call
>   ps.setInt(1, id);
>   ps.setObject(2, value);
>   ps.addBatch();
> on the same statement, you need to add synchronization to ensure that the addBatch()
call in one thread doesn't end up using one or more parameter values set by the other thread.
> --
> Knut Anders
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