I'd been doing some stress testing of my mysql application today, and I was hitting some weird cases. Several transactions were deadlocking - this was expected - but the number of records that got inserted into my table was more than the number that I expected after subtracting errors.

My test was fairly simple:

Fork 15 processes

Insert and update 100 records in each process, running each INSERT/UPDATE pair inside one transaction

ROLLBACK on error

Either the INSERT or the UPDATE was expected to fail due to deadlock, and the whole transaction should have rolled back leaving no record in the table.

Before I go on, I should mention that I was using InnoDB, which does support transactions.

What I expected was that the total number of records in the table + the total number of INSERT/UPDATE aborts due to deadlock should be equal





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