Optimizing mysql IN query having large values

Question

I have a mysql query like

 SELECT `tbl_ticket`.`id`, `tbl_ticket`.`hd_user_username`, 
`tbl_ticket`.`hd_user_email`, `tbl_ticket`.`ticket_title`, 
`tbl_complain_type`.`complains` FROM `tbl_ticket` LEFT JOIN 
`tbl_ticket_complain` ON tbl_ticket_complain.ticket_id=tbl_ticket.id 
LEFT JOIN `tbl_complain_type` ON tbl_complain_type.id=tbl_ticket_complain.complain_id 
LEFT JOIN `tbl_assignment` ON tbl_assignment.ticket_id=tbl_ticket.id 
WHERE ((((`hd_user_username` LIKE '%searchterm%') 
AND (`tbl_assignment`.`id` IN ($array))) 
OR (`hd_user_email`='searchterm')) 
OR (`ticket_title`='searchterm')) OR (`tbl_complain_type`.`complains`='searchterm')

$array contains around 7000 values like `$array=array(1,2,3,..)`

This query takes around 8 seconds to execute. Is there any alternative solution for this query ? The value of $array is got from another query

select max(id) from tbl_assignment group by ticket_id

The slowness of query is due to multiple joins between tables

Answer 1

If the values in the array use in you IN clause come from a select you could use the fact that
An IN clause is equivalent to an inner join so you could use a inner join between your_table_with_id and the table.column you need for match eg:

  SELECT `
      tbl_ticket`.`id`
      , `tbl_ticket`.`hd_user_username`
      , `tbl_ticket`.`hd_user_email`
      , `tbl_ticket`.`ticket_title`
      , `tbl_complain_type`.`complains` 
  FROM `tbl_ticket` 
  LEFT JOIN `tbl_ticket_complain` ON tbl_ticket_complain.ticket_id=tbl_ticket.id 
  LEFT JOIN `tbl_complain_type` ON tbl_complain_type.id=tbl_ticket_complain.complain_id 
  LEFT JOIN `tbl_assignment` ON tbl_assignment.ticket_id=tbl_ticket.id 
  INNER JOIN your_table_with_id ON `tbl_assignment`.`id` = JOIN your_table_with_id.id
  WHERE ((((`hd_user_username` LIKE '%searchterm%') 
  OR (`hd_user_email`='searchterm')) 
  OR (`ticket_title`='searchterm')) OR (`tbl_complain_type`.`complains`='searchterm')

Remeber also that the content of values use IN clause is limited and fail when the limit is exceeded

and in your case

  SELECT `
      tbl_ticket`.`id`
      , `tbl_ticket`.`hd_user_username`
      , `tbl_ticket`.`hd_user_email`
      , `tbl_ticket`.`ticket_title`
      , `tbl_complain_type`.`complains` 
  FROM `tbl_ticket` 
  LEFT JOIN `tbl_ticket_complain` ON tbl_ticket_complain.ticket_id=tbl_ticket.id 
  LEFT JOIN `tbl_complain_type` ON tbl_complain_type.id=tbl_ticket_complain.complain_id 
  LEFT JOIN `tbl_assignment` ON tbl_assignment.ticket_id=tbl_ticket.id 
  INNER JOIN (
    select max(id) as id
    from tbl_assignment 
    group by ticket_id
  ) t ON `tbl_assignment`.`id` = t.id
  WHERE ((((`hd_user_username` LIKE '%searchterm%') 
  OR (`hd_user_email`='searchterm')) 
  OR (`ticket_title`='searchterm')) OR (`tbl_complain_type`.`complains`='searchterm'))

Answer 2

This is basically your query:

SELECT . . .
FROM tbl_ticket t LEFT JOIN 
     tbl_ticket_complain tc
     ON tc.ticket_id = t.id LEFT JOIN 
     tbl_complain_type tct
     ON tct.id = tc.complain_id LEFT JOIN
     tbl_assignment a
     ON a.ticket_id = t.id 
WHERE (((hd_user_username LIKE '%searchterm%' AND
         a.id IN ($array)
        ) OR
        `hd_user_email`='searchterm'
       ) OR
       ticket_title = 'searchterm'
     ) OR
     tct.complain` = 'searchterm';

The issue with performance has nothing to do with IN . In fact, MySQL optimizes IN , as explained in the documentation :

If all values are constants, they are evaluated according to the type of expr and sorted. The search for the item then is done using a binary search. This means IN is very quick if the IN value list consists entirely of constants.

You are not going to get faster than an IN list with constants.

The problem with your query is the string of OR s. These make is almost impossible for the optimizer to use indexes -- so the full result set has to be created and then filtered down.

It is hard for me to see how to improve this in your query. Sometimes, splitting a query into simpler chunks and connecting them using union or union all does the trick. Your conditions are a bit hard to follow, making that approach difficult for an outsider.