Zeoslib Portal

Hello,

I want to change my application to run multithreaded.

Right now I am using zeos and firebird. It inserts data sets in
a sequential way into database.

In general this could be done in parallel. But I wonder if zeos supports
this?

Sequence:
Insert;
dataset.fieldbyname('xxx')=xxx;
post;

How can this be done threadsafe?

Thanks!

You could pool your database connections and then get one connection for each thread from that pool.

Regards

Sandeep

Thanks for the quick answer!

Can u give me a example?

Thx
Andreas

Hi Andreas

You will have to declare a function that takes care of managing and returning a connection TO and FROM the Pool. There should be some docs on the web on this topic.

So in your thread you could do something like

lZCon := GetConFromPool;
try
// Assign connection to all your controls that connect to database.
finally
ReturnConToPool(lZCon);
end;

This is the basic structure that I have used in my apps and has worked fine for me.

Hope that helps.

Regards

Sandeep

Isn't it enough to open and close a connection in each thread here?

Hi Sandeep,

would it also work to do a connection.create() and a
freeandnil(connection) in each thread?

Thx
Andreas

r2d2 wrote:Hi Sandeep,

would it also work to do a connection.create() and a
freeandnil(connection) in each thread?

Thx
Andreas

It would do the trick, but with a connection pool you'll have some persistent connections available, loosing the weight of connection and disconnecting in all threads.

Well, you get the idea.

Hi,

That worked perfect! Thx!

But now my dbgrid from the main app doesnt update. It uses
a different connection.

Any idea how to get this updated?

Thx
Andreas

Could you give a bit more details about your app and how you have structured it?

Regards

Sandeep

The app has the following db design:

Main: TZCon1->TZQuery1->TDataSource->DBGrid

it issues threads with the following structure

Threadn: TZCon2->TZQuery2->insert/update/...

While running the threads work but Main doesnt update.
After close and restart of Main I get all records displayed in DBGrid.

Is this a buffer problem? Or invalidate/update problem?

Regards
Andreas

Hello,

I got it. The TransactIsolationLevel of ZCon was not set properly.

Many thanks for all who contributed here!!!

Andreas