How to speed up Update in a loop on a large table?

Question

MySQL

There is a table table1 with 3 million rows. There is an index on id.
It is necessary to update one field by id in a cycle in php for all rows in sequence.
I wrote a script in php, everything is fine, but every 1000 update is processed in 8 seconds. So I will wait until tomorrow)
Explain looked, the index is used. What could be the problem?
innodb table

Answer 1

Maybe I misunderstood, but why run a cycle here if the entire table is updated, where all IDs are sorted sequentially.
It's just possible

UPDATE table1
SET field = 'value'

Answer 2

1. create temporary table t_tmp ...
2. insert into t_tmp values (...), (...), ...
3. update ...
4.drop temporary table t_tmp

Answer 3

I ran into this on a project with huge prices and there the simplest solution is to delete and re-insert in portions