mySql performance question about updating indexed field

Question

I have a large table with a multi-part index. I need to run several queries to update a field that is part of the index. Basically every row will be updated. Would it be faster to drop the index, do all the updates and then re-add it?

EDIT: Added question, why does it take so freaking long to DROP an index? Am I missing something or shouldn't this take about .5 seconds?

Answer 1

There are a number of factors involved. My guess is that yes it would be faster to drop the index and rebuild it after the updates. Your best bet, though, is to test it and see which is faster.

Answer 2

Why does it take so freaking long to DROP an index?

You may want to check the following:

• Dropping all indexes from a table is slow
• Why does mysql drop index very very slow in a large table?