## Proposed changes 1. Use column idx of ref block instead of new block to indicate the ref column. 2. Rename some variables to clarify their meanings. 3. Clarify some log msg. 4. Add a minimal case to verify the change.
## Proposed changes 1. Use column idx of ref block instead of new block to indicate the ref column. 2. Rename some variables to clarify their meanings. 3. Clarify some log msg. 4. Add a minimal case to verify the change.