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From:Eric Robinson Date:May 31 2013 11:23pm
Subject:RE: Are There Slow Queries that Don't Show in the Slow Query Logs?
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> -----Original Message-----
> From: Vikas Shukla [mailto:myfriendvikas@stripped] 
> Sent: Thursday, May 30, 2013 7:19 PM
> To: Robinson, Eric; mysql@stripped
> Subject: RE: Are There Slow Queries that Don't Show in the 
> Slow Query Logs?
> 
> Hi,
> 
> No, it does not represents the time from request to response 
> not does it includes the time that is spent in waiting for 
> the locks to be released.
> The slow query log consists of SQL statements that took more 
> than long_query_time seconds to EXECUTE. The default value of 
> long_query_time is 10.
> The time to acquire the initial locks is not counted as 
> execution time.
> mysqld writes a statement to the slow query log after it has 
> been executed and after all locks have been released, so log 
> order might differ from execution order.
> 
> Lets take an example, if a query is received at 10:00 hrs and 
> it waits till 10:05 hrs , it starts getting executed at 
> 10:05:00 and completed at 10:05:24 (HH:MM:SS). So, here it 
> took 24 seconds to execute. So only
> 24 seconds is counted.
> So if long_query_time is equal to 10, which is by default, 
> this would be logged in slow query log as it takes more than 
> 10 seconds to execute.
> 
> Sent from my Windows Phone From: Robinson, Eric
> Sent: 31-05-2013 03:48
> To: mysql@stripped
> Subject: Are There Slow Queries that Don't Show in the Slow 
> Query Logs?
> As everyone knows, with MyISAM, queries and inserts can lock 
> tables and force other queries to wait in a queue. When that 
> happens, does the time shown in the slow query logs represent 
> the whole time from when the server received the request to 
> when the response was sent to the client? Or is the time a 
> query spends waiting for a table lock to be released omitted 
> from what is recorded in the slow query logs?
> 
> --
> Eric Robinson
> 
> 

Very good answer, Vikas. Thank you for the clarification!

--Eric




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Thread
Are There Slow Queries that Don't Show in the Slow Query Logs?Eric Robinson30 May
RE: Are There Slow Queries that Don't Show in the Slow Query Logs?Vikas Shukla31 May
  • RE: Are There Slow Queries that Don't Show in the Slow Query Logs?Eric Robinson31 May