Re: "Multiple BTM with multiple jdbc datastores" + "jdbc prepareStatements"

Hi,

Nothing in JTA or BTM prevents you from using the serializable isolation level. Maybe your database has such limitation though.

If you want to use prepared statements, just make sure you always call Connection.prepareStatement() with the exact same SQL queries and enable the prepared statement cache and the BTM connection pool will do the rest for you.

Just keep in mind that not all databases benefit from preparing statements. Depending on the DB / JDBC driver implementations you may not get any performance benefit.

Ludovic

2011/10/19 Fazool <fazoolmein@...>

Hi,

I am using BTM for prototyping a shared nothing database; where a
transaction can touch multiple databases so I need two-phase commit. I will
appreciate if you can answer the following:

1) As per documentation, I can use multiple BTM with a single datastore. I
want to use multiple BTMs (running on different machines) for multiple jdbc
datastores, where a transaction can update rows on different datastores.
According to my experiments, we cannot have 'Seriablizable' isolation level
in this context. Is this correct?

2) I am using prepareStatements in jdbc. As I see, I have to 'prepare' a
prepareStatement everytime I want to run a query. For example:

  btm.begin()
  PrepareStatement p = con.prepareStatement("...");
  p.setInt(1,1);
  ...
  p.executeUpdate();
  btm.commit();

Creating a statement everytime I want to run a transaction has performance
penalties. I am unable to do something like:

  PrepareStatement p = con.prepareStatement("...");

  btm.begin()
  p.setInt(1,1);
  p.executeUpdate();
  btm.commit();

  btm.begin()
  p.setInt(1,2);
  p.executeUpdate();
  btm.commit();

i.e. use the same prepare statement multiple times. Is setting a high value
of PreparedStatementCacheSize going to improve efficiency of
"con.prepareStatement("...");" within a btm.begin()/end()? I ran some basic
experiments, and PreparedStatementCacheSize didnt help much. Can you kindly
comment on how to make this efficient?

Thank you very much!

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