I have an update query that selects data from a table (HST) and updates it into another table (PCL). The PCL table contains ~30000 rows while the HST table contains about 1.1 million rows. I have multiple (composite) indexes on HST and despite being a large table all queries on it are fairly quick (~2-3 sec). However, when I attempt to select rows from this table and update PCL, it takes 3-4 hours, and in most cases I get "Lock wait timeout exceeded; try restarting transaction" errors and I have to keep trying until it works.
UPDATE PCL SET `T2A` = (SELECT HST.`Date` from `HST` WHERE HST.`SYM`=PCL.INST AND HST.`DATE` >= PCL.Date AND HST.`HP` >= PCL.T2 order by HST.`Date` limit 1) WHERE `BS` = 'B' AND `T1A` IS NOT NULL;
Is there a way I can rewrite the above query so that it runs faster?