Hi all,
The small demo script below makes ADO calls to a Microsoft Access (Jet)
database via win32com. But it fails in a potentially dangerous way;
"SELECT int * int;" can return None with no warning if the result is
large enough. This can also occur if one or both of the operands is a
column reference.
The same SQL run as a Query inside the Access GUI works as expected.
Manually changing one of the ints to a Single by appending ".0" works as
expected.
Any ideas about where I need to look next to find the cause of, and then
fix, this behavior?
Robert Brewer
System Architect
Amor Ministries
[EMAIL PROTECTED]
# demo_access_overflow.py
import os
import win32com.client
adOpenForwardOnly = 0
adLockReadOnly = 1
dbname = "test.mdb"
def create_db():
cat = win32com.client.Dispatch(r'ADOX.Catalog')
cat.Create("PROVIDER=MICROSOFT.JET.OLEDB.4.0;DATA SOURCE=%s;" %
dbname)
cat.ActiveConnection.Close()
def fetch(query, conn):
try:
# Call conn.Open(query) directly, skipping win32com overhead.
res = win32com.client.Dispatch(r'ADODB.Recordset')
res.Open(query, conn, adOpenForwardOnly, adLockReadOnly)
data = res.GetRows()
finally:
res.Close()
return data
if __name__ == '__main__':
try:
create_db()
conn = win32com.client.Dispatch(r'ADODB.Connection')
try:
conn.Open("PROVIDER=MICROSOFT.JET.OLEDB.4.0;DATA SOURCE=%s;"
% dbname)
# This works fine.
assert fetch("SELECT 86400;", conn) == ((86400,),)
# This fails because data is ((None,),)
data = fetch("SELECT 62647 * 86400;", conn)
assert (data == ((62647 * 86400,),)), data
finally:
conn.Close()
finally:
if os.path.exists(dbname):
os.remove(dbname)
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