Question

I’ve struggled with this one for a long time. This query runs fairly fast on a smaller data set but when the tables grow to 100k+ rows it takes from 30s to several minutes to run:

SELECT  accounts.id 
        , accounts.name 
        , ..etc..
FROM    accounts   
        LEFT JOIN (
          SELECT  distinct secr.record_id as id 
          FROM    securitygroups secg
                  INNER JOIN securitygroups_users secu 
                    ON secg.id = secu.securitygroup_id 
                       AND secu.deleted = 0 
                       AND secu.user_id = 'seed_chris_id'
                  INNER JOIN securitygroups_records secr 
                    ON secg.id = secr.securitygroup_id 
                       AND secr.deleted = 0 
                       AND secr.module = 'Accounts'
          WHERE   secg.deleted = 0
        ) securitygroup_join ON securitygroup_join.id = accounts.id  
WHERE   (( accounts.assigned_user_id ='seed_chris_id' 
           OR securitygroup_join.id is not null)) 
        AND accounts.deleted=0 
ORDER BY 
        accounts.date_entered 
DESC    LIMIT 0,21

Basically it should return all rows where the user owns the record (accounts.assigned_user_id) or is a member of a group associated to the record (securitygroup_join.id is not null). This query gets built in a particular way by the framework so facing some constraints. A possible solution that cannot be easily implemented would be to change this to a UNION. Would like to avoid that route. In the past did a “where…in” clause but that performed even worse. I can add to the join, where clause, or manipulate indexes as needed but any other drastic changes to the query structure cannot be easily done.

Answer 1

You could try a WHERE EXISTS instead of a LEFT JOIN. For example:

SELECT  accounts.id 
        , accounts.name 
        , ..etc..
FROM    accounts   
WHERE   (( accounts.assigned_user_id ='seed_chris_id' 
       OR EXISTS (SELECT  1
                  FROM    securitygroups secg
                          INNER JOIN securitygroups_users secu 
                            ON secg.id = secu.securitygroup_id 
                               AND secu.deleted = 0 
                               AND secu.user_id = 'seed_chris_id'
                          INNER JOIN securitygroups_records secr 
                            ON secg.id = secr.securitygroup_id 
                               AND secr.deleted = 0 
                               AND secr.module = 'Accounts'
                       WHERE   secr.record_id = accounts.id
                               AND secg.deleted = 0)
       )) 
    AND accounts.deleted=0 
ORDER BY 
    accounts.date_entered 
DESC    LIMIT 0,21

I haven’t tested this, so it may not perform better, but it’s worth trying.