简单的MySQL查询长16秒

Question

I am running a 8gb ram, quad-core, SSD cloud server.

Most DB queries are fast, but one query updating only one column for one row is taking up to 16 seconds, according to New Relic.

My query is:

UPDATE user SET ad=$currentAdSet WHERE ckey='$_COOKIE[ckey]'

And I am using the mysql_query("") php function to execute the query.

Mu user table has around 43000 rows and a simple structure.

Why is this query taking so long? Any ideas?

Answer 1

Try to add an index on ckey and check the timing again. I would advise some reading on indexes.

BTW, using directly a cookie value might lead to SQL injection

Answer 2

You can try and see what is making it be so slow by using EXPLAIN . Then, based on the bottle necks you see, use indexes.

Answer 3

ensure ckey is indexed and, if not needed, ad is NOT indexed.

the first will allow faster selection of records, the second faster update

hope this helps