Slow Queries for no clear reason

[Infinitive]

I'm trying to track some slowness in my system, which I believe is coming from the MySQL db.  I started up log-slow-queries to make sense of it and there's a lot of info, but no clear explanations.  Some queries are taking much longer than they should for no apparent reason.  Like this one:

 

# User@Host: AccountLogin[AccountLogin] @ localhost []

# Query_time: 9  Lock_time: 0  Rows_sent: 0  Rows_examined: 0

DELETE FROM Stored_List WHERE StorageID = 162725;

 

StorageID is in this case the Primary Key.  The table's large but not enormous, at under 24,000 rows.  And it only has 7 columns.

 

So why should this query take so long to process?  Zero rows were examined (because it was based off of a key) and thankfully the lock time was zero.  What's the holdup?

 

That's just an easy example, I could find others: an update based off the primary key that takes 18 seconds (different table).  Or this Select, off the same table:

 

# User@Host: AccountLogin[AccountLogin] @ localhost []

# Query_time: 7  Lock_time: 0  Rows_sent: 1  Rows_examined: 8

SELECT count(1) AS Items FROM Stored_List WHERE Stored_List.WarehouseID = 3979;

 

Yes it had a couple rows to look at, but 7 seconds to examine 8 rows?

 

I'm still new at this from the analyzing side so I'm trying to make sense of it.  I also ran a mysqlreport that looked normal except that com_: change_db was high, and I'm trying to figure out what that means too.

[fenway]

Run the EXPLAIN for each of those.