Question

I’m only a dabbler in databases – using them for backends for basic web applications, never anything enterprise.

I’ve recently needed to work with two tables – one with 130,000 rows and the other with 29,000 rows. They have similar data and I need to pull from them with some sort of JOIN statement. Unfortunately this seems to cause issues and the query sits and hangs.

The query is as follows:

SELECT * 
FROM call_status LEFT JOIN queue_log 
ON call_status.callId = queue_log.callid 
ORDER BY call_status.callId DESC limit 10;

When checking the processlist, I see the following:

Query   643 Copying to tmp table    SELECT * FROM call_status LEFT JOIN queue_log ON call_status.callId = queue_log.callid ORDER BY call 

Yes, the query has been running for over 10 minutes.

I’ve run an explain and this it the output:

1   SIMPLE  call_status ALL (null)  (null)  (null)  (null)  28954   Using temporary; Using filesort
1   SIMPLE  queue_log   ALL ix_queue_log_callid (null)  (null)  (null)  130419  

I’ve run a SHOW INDEX on both tables, both look fine to me:

call_status:

call_status 0   PRIMARY 1   callId  A   28954   (null)  (null)      BTREE   
call_status 0   ix_order_callId 1   callId  A   28954   (null)  (null)      BTREE    

queue_log:

queue_log   1   ix_queue_log_callid 1   callid  A   26083   (null)  (null)      BTREE   

I’m at a complete loss, and it’s 2am here.

Answer 1

Can you try this?:

SELECT * 
FROM 
      ( SELECT *
        FROM call_status 
        ORDER BY callId DESC 
        LIMIT 10
     ) AS st
  LEFT JOIN 
      queue_log AS qlog 
    ON 
      st.callId = qlog.callid 
ORDER BY 
      st.callId DESC 
LIMIT 10