[Solved] SQL query very slow - How can I improve it?

How to optimize this SQL query?

In case you have your own slow SQL query, you can optimize it automatically here.

For the query above, the following recommendations will be helpful as part of the SQL tuning process.
You'll find 3 sections below:

  1. Description of the steps you can take to speed up the query.
  2. The optimal indexes for this query, which you can copy and create in your database.
  3. An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
  1. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
The optimized query:
SELECT
        * 
    FROM
        mytable 
    LEFT JOIN
        table1 AS m1 
            ON mytable.idA = m1.K 
    LEFT JOIN
        table1 AS m2 
            ON mytable.idB = m2.K 
    LEFT JOIN
        table1 AS m3 
            ON mytable.idC = m3.K 
    LEFT JOIN
        table1 AS m4 
            ON mytable.idD = m4.K 
    LEFT OUTER JOIN
        table2 AS t1 
            ON mytable.idK1 = t1.idK1 
            AND mytable.idK2 = t1.idK2 
    LEFT OUTER JOIN
        table3 
            ON t1.idT = table3.idT 
    WHERE
        m1.K = 'my_value' 
        OR m2.K = 'my_value' 
        OR m3.K = 'my_value' 
        OR m4.K = "my_value"

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* original question posted on StackOverflow here.