When we added the column store testing scenario to test_hs18, we found that the following tests fail when checking values after committing transactions with and without timestamps:

• test_multiple_older_readers
• test_multiple_older_readers_with_multiple_mixed_mode
• test_read_timestamp_weirdness

We also found test_hs11 and test_hs18 fail for similar reasons.

This ticket is to add mixed mode transaction support for column store to WiredTiger and to re-enable the mixed mode testing in test_hs11, test_hs18 and  test_hs19 and verify that all tests pass.