Added 4 new test cases to verify the join optimization fix:
- INTERSECT query: Common user_ids in both streams
- EXCEPT query: Users without orders
- INTERSECT with WHERE clause: Active users with orders
- EXCEPT with multiple columns: Users details without orders
Also improved test_joinqueries.py by adding a 3-second sleep after data
ingestion to allow proper indexing before querying.
Co-authored-by: Claude <noreply@anthropic.com>