Hi,

Good catch, thanks. Logged as PYFB-34 and fix committed. Please checkout
the the latest version from our Subversion at:

http://svn.code.sf.net/p/firebird/code/python/fdb/trunk

and let me know whether it solved your problem.

best regards
Pavel Cisar
IBPhoenix

Dne 30.4.2013 12:20, josef_gschwendtner napsal(a):

>
> Hi,
>
> We got a problem when we use the Firebird driver for Python (fdb) inside
> a connection pool. If a single connection is used for the execution of
>
> many queries and each query uses a separate cursor instance we observed
> an increasing memory usage on the server side (the fbserver process).
>
> Only when the connection gets closed the memory usage of the fbserver
> process gets back to a "normal" value.
>
> An equal situation can be simulated with this short python script.
>
>
>
> import fdb
>
>
>
>
>
> con = fdb.connect(dsn='localhost/3050:C:\\Development\\DB\\mydb.fdb',
> user='sysdba',
> password='masterkey')
>
>
>
> for i in range(10000):
>
> cur = con.cursor()
>
> cur.execute( "select * from RDB$Relations")
>
> for row in cur.fetchall():
>
> print i, row[0]
>
> con.commit()
>
> t = raw_input('Press Key')
>
> con.close()
>
>
>
> print "Finished"
>
>
>
> When the loop has finished and before closing the connection the
> fbserver process uses almost one GB of memory. This is independent of
> the table being used.
>
> RDB$Relations is only used for demonstration. The same happens also with
> every other table. After closing the connection everything is fine on
> the server
>
> (fbserver memory usage is back to 7 MB).
>
>
>
> We found out that releasing the Cursor instance does not permanently
> free the prepared statement on the server side. During the destructor of
> the Cursor instance
>
> the internal managed PreparedStatement instances will also be released.
> This will call the method _close from PreparedStatement. Inside the
> _close Method the
>
> release of the server side statement resource will only be triggered if
> there is an open connection. But to get this connection the
> PreparedStatement instance uses the
>
> cursor Attribute which is a weak reference to the Cursor instance. But
> this Cursor instance is no longer available because the program
> execution is inside the
>
> destructor (__del__) of this cursor. The weak reference is dead.
>
>
>
> It seems that Cursor and PreparedStatement instances are released on the
> client side but the following statement from the _close method of
> PreparedStatement doesn't get executed.
>
>
>
> api.isc_dsql_free_statement(self._isc_status, stmt_handle,
>
> ibase.DSQL_drop)
>
>
>
> But this statement is required for releasing the server side resources
> and also the memory used for these resources.
>
> Thanks for your help,
>
> Josef
>
>