Can having a LIMIT on DELETE degrade performance dramatically? I have a database project in php and mysql.  For, hopefully redundant, data security I added a LIMIT 1 to the delete($uniqueID) php function we use.

Nobody cared because records really aren't supposed to be deleted often from this database.  However we recently got a massive jump in the response time for this server.  By massive I mean approximately four times worse than our previous worst heavy load performance.

The culprit seems to be a series of 100 individual DELETE statements from a small table, about 7 columns and 150 records.  This doesn't seem right.  Is it possible that this newly added LIMIT 1 is obliterating performance?

I don't think so, but the data logging I have suggest that it is.
No, at least not in this case.

The evidence pointing towards a DELETE ... LIMIT 1 was real, but not entirely accurate.  The real issue here was a PHP script that called hundreds of unnecessary queries in order to execute the suspected DELETE ... LIMIT 1 query.

Using MySQL's log all queried on a test environment lead to the solution to this problem.