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From Pavel Bortnovskiy <pbortnovs...@jefferies.com>
Subject RE: concurrent execution of Statement's .addBatch() and .executeBatch()
Date Fri, 07 Dec 2012 15:53:44 GMT
Thank you, Knut.

Yes, my app is doing precisely that, so I may have to use a single thread to operate on the
same PreparedStatement, or "serialize" access to it that only one thread may set objects and
execute.

May I ask a related question, then?

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?

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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