We use ODP.NET to perform queries on Oracle databases, and normally it works fine. There is a particular database, and a particular view in that database, though, that we just can’t complete a query on from .NET. For example:
SELECT some_varchar_field FROM the_view WHERE ROWNUM < 5;
If I execute this query from within Oracle SQL developer, it finishes in less than a second. If I do an identical query from our .NET application using ODP.NET, it hangs and eventually produces an “ORA-03135: connection lost contact” error. I think that limiting it to just a few rows eliminates the possibility that it is as FetchSize issue.
There are other queries I can execute successfully, but they are slower from our program than from SQL Developer. Again, I realize SQL Developer only gets data for the first 50 rows initially, but I think the ROWNUM condition takes that out of the equation.
What might be different about the connection or command that Oracle SQL Developer is using vs the one our application is using that would cause a difference in speed?
Unfortunately, I do not have access to the server (other than to run Oracle queries against it).
Thank you.
UPDATE: I have tried the same query with Microsoft’s Oracle provider and it executes very quickly. Unfortunately, that provider is deprecated so this is not a long term solution.
It had nothing to do with the ODP.NET provider. The problem was that the library we use to create connections for us (which, of course, is not used by Oracle SQL Developer, and which I did not use when I tried the Microsoft provider) was always executing the following statements before doing anything:
These make Oracle case-insensitive. But, they also render all conventional indexes useless. Because we were querying from a View, it had ordering built in. And because we don’t own the database, we can’t make the indexes linguistic to fix the performance problem.
Providing a way to not execute those statements in this (rare) scenario fixed the problem.