alexander.gorrod@mongodb.com, vamsi.krishna:

There's a CONFIG and discussion in WT-4366, it's a problem found running the CONFIG from WT-3898.

In summary, WiredTiger is returning WT_PREPARE_CONFLICT to a repeated read in a snapshot transaction. (In format, a snapshot isolation transaction does a read, and then when it repeats the read before committing, it gets WT_PREPARE_CONFLICT).

I'll fix up format to loop on WT_PREPARE_CONFLICT in WT-4366, but michael.cahill suggested there were potential improvements that could be made in the WiredTiger library.