[PyDB2-discuss] Db2 module issues.

[Yuval T. <yu...@il...>]

Hello everyone -
I've been testing the module extensively in the past few days using the 
following code:

import DB2,sys,random

for x in range(5000):
    conn = DB2.Connect('uvrerch','db2rerch','db2rerch')
    curs = conn.cursor()
    id = random.randint(0, 500)
    curs.execute("SELECT * FROM MYTABLE WHERE ID=%d" % id)

Here are some comments:
1.  In line 414 - default autocommit mode was changed to "no auto 
commit" - this change causes the select query to consume plenty of 
memory.  Of course, if I add a conn.commit() after the execute statement 
(or call conn.autocommit(1) after creating the connection object), the 
memory is stable.  Is this the kind of behaviour that we want?  I mean 
"commit" is meant  to be called only after inserts, no ?

2.  In the dealloc functions (for both cursor, and connection objects) 
we call PyMem_DEL after we initialized those objects with PyObject_NEW.  
According to the python api, objects should be deleted using PyObject_DEL.

3.  In DB2_connection_object_cursor (line 666 :-), there's a commented 
out call to Py_INCREF(self) right after the assignment of cursor->conn = 
self.  If we want to make sure that the connection object stays alive 
while the cursor is alive, we must call incref ( and decref upon 
destruction ).

4.  We clear the cursor data prior to fetching instead of after fetching 
- this can cause leaks.  After we converted the data to pyobjects, we 
need to clear the data.  So, to fix this (potential) problem I did the 
following:
A.  I changed the name of DB2_cursor_object_fetchone to 
DB2_cursor_object_do_fetch, and created the following new wrapper function:

static PyObject *
DB2_cursor_object_fetchone(DB2CursorObject *self, PyObject *args)
{
        PyObject *pRet = DB2_cursor_object_do_fetch(self, args);
        DB2_cursor_object_clear_data(self);
        return pRet;
}

B.  In fetchall and fetchmany, I changed the calls from fetchone to 
do_fetch, and added a calls to DB2_cursor_object_clear_data(self); at 
the end of the loops.

That's what I got till now.
I have those code changes - and I'm currently testing them.  They're looking good.
If you want me to commit those changes to the CVS, then drop me a note.

-- 
Yuval Turgeman
Content Technology, Aduva LTD.