mysql insert race condition

Question

How do you stop race conditions in MySQL? the problem at hand is caused by a simple algorithm:

1. select a row from table
2. if it doesn\'t exist, insert it

Answer 1

what you want is LOCK TABLES

or if that seems excessive how about INSERT IGNORE with a check that the row was actually inserted.

If you use the IGNORE keyword, errors that occur while executing the INSERT statement are treated as warnings instead.