Lineage Diff

Requirements

Agent: any (read-only analysis) Tools used: lineage_check, read, bash (for git operations), glob

Compare column-level lineage between two versions of a SQL model to identify changes in data flow.

Workflow

1. Get the original SQL — Either:

   • Read the file from disk (current committed version)
   • Use git show HEAD:path/to/file.sql via bash to get the last committed version
   • Accept the "before" SQL directly from the user

2. Get the modified SQL — Either:

   • Read the current (modified) file from disk
   • Accept the "after" SQL directly from the user

3. Run lineage on both versions:

   • Call lineage_check with the original SQL
   • Call lineage_check with the modified SQL

4. Compute the diff:

   • Added edges: Edges in the new lineage that don't exist in the old
   • Removed edges: Edges in the old lineage that don't exist in the new
   • Unchanged edges: Edges present in both

5. Report the diff in a clear format:

Lineage Diff: model_name
═══════════════════════════

+ ADDED (new data flow):
  + source_table.new_column → target_table.output_column

- REMOVED (broken data flow):
  - source_table.old_column → target_table.output_column

  UNCHANGED: 5 edges

Impact: 1 new edge, 1 removed edge

Usage

The user invokes this skill with a file path:

• /lineage-diff models/marts/dim_customers.sql — Compare current file against last git commit
• /lineage-diff — Compare staged changes in the current file

Edge Matching

Two edges are considered the same if all four fields match:

• source_table + source_column + target_table + target_column

The transform field is informational and not used for matching.

Use the tools: lineage_check, read, bash (for git operations), glob.