Originally reported at

If tables have slight modifications, pt-table-sync fails to find them, thus fix the differences.

How to Repeat.

Here are the steps I used to reproduce the silent failure:

Step 1) Create tables in both databases:

Step 2) create some rows:

Step 3) run the sync:

Step 4) confirm the data sync'ed:

Step 5) make changes in the source table which invert unique keys

Step 6) re-run the sync:

Notice that pt-table-sync reports no changes and no errors:

Step 7) Confirm surprising result:

We have a test for this case: t/pt-table-sync/issue_920.t, but no fix.

pt-table-checksum, likely, also affected.