Re: Slow UPDATE's on a large table

[Rick James]

Sounds like a missing or inadequate INDEX. Plz show us the UPDATE.

Also, please provide
* SHOW CREATE TABLE tbl\G -- engine, indexes
* SHOW TABLE STATUS LIKE 'tbl'\G -- sizes
* SHOW VARIABLES LIKE '%buffer%'; -- cache size
and surround them with [ code ] and [ / code ]

You could try
ANALYZE TABLE
to get it to recompute the statistics.

LOCK/UNLOCK around a single statement (such as an UPDATE that modifies 1000 rows) has no impact. LOCK/UNLOCK around a sequence of statements (in MyISAM tables) could improve speed _some_, but at the expense of locking out other queries.