Greetings,

We're running MySQL 3.23.47 on MacOS X 10.1.2. We've got a rather large table ( 200,000+ records, 120+ columns) and some simple queries on that table have pretty inconsistent performance. Due to licensing issues I can't give an actual example of the table, but here is an equivalent example:

Field1 and Field2 are both unsigned integers IndexField1 is an unsigned integer and is the primary key

select Field1,Field2 from table1 where IndexField1 = 345232;

We ran this query will different values for IndexField1, sometimes it would return in around 0.01 seconds, other times it would take as long as 9 seconds. There was no other load on the database when this was occurring, and it was specific to certain records (one IndexField1 would always return around 8 seconds, others would always return around 0.01 seconds).

Is there any kind of reasonable explanation for this behavior? Is it perhaps because of where the records are situated on the hard disk (seek times)? Is it maybe a caching issue?