TableNibbler choosing wrong fields for composed primary key on MariaDB

Reopening just to remove the fix version

Here is the explanation:

I've populated the table as defined in the description with 0 < f1_key < 100 and 0 < f3_key < 100.

To be able to choose the correct boundaries for the compose key, pt-table-checksum runs a query like this: (example for the second chunk using --chunck-size=100)

using these params:

As you can see, f1_id is being used in the comparison as an individual field (`f1_id` > ?) and with f3_id (`f1_id` > ?) so f1_id appears twice.
That's the reason pt-table-checksum uses 3 fields for every chunk.

Reopening to run more tests

After analyzing how it works I found that the keys and boundaries are OK.

Since the select key is compound, it is necessary to try all combinations so in the case reported, it is correct to choose f1_id twice.