EverSQL Database Performance Knowledge Base

The optimization process and recommendations:

1. Avoid LIKE Searches With Leading Wildcard (query line: 59): The database will not use an index when using like searches with a leading wildcard (e.g. '% turtles %'). Although it's not always a satisfactory solution, please consider using prefix-match LIKE patterns (e.g. 'TERM%').
2. Avoid OFFSET In LIMIT Clause (query line: 70): OFFSET clauses can be very slow when used with high offsets (e.g. with high page numbers when implementing paging). Instead, use the following \u003ca target\u003d"_blank" href\u003d"http://www.eversql.com/faster-pagination-in-mysql-why-order-by-with-limit-and-offset-is-slow/"\u003eseek method\u003c/a\u003e, which provides better and more stable response rates.
3. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
4. Prefer Sorting/Grouping By Columns From Same Table (modified query below): The database cannot use an index for the sorting/grouping operation if the ORDER BY/GROUP BY clause contains columns from different tables.
5. Push Filtering Conditions Into Subqueries (modified query below): Parts of the WHERE clause can pushed from the outer query to a subquery / union clause. Applying those conditions as early as possible will allow the database to scan less data and run the query more efficiently.
6. Use Numeric Column Types For Numeric Values (query line: 4): Referencing a numeric value (e.g. 10) as a string in a WHERE clause might result in poor performance. Possible impacts of storing numbers as varchars: more space will be used, you won't be able to perform arithmetic operations, the data won't be self-validated, aggregation functions like SUM won't work, the output may sort incorrectly and more. If the column is numeric, remove the quotes from the constant value, to make sure a numeric comparison is done.
7. Use Numeric Column Types For Numeric Values (query line: 5): Referencing a numeric value (e.g. 10) as a string in a WHERE clause might result in poor performance. Possible impacts of storing numbers as varchars: more space will be used, you won't be able to perform arithmetic operations, the data won't be self-validated, aggregation functions like SUM won't work, the output may sort incorrectly and more. If the column is numeric, remove the quotes from the constant value, to make sure a numeric comparison is done.
8. Use Numeric Column Types For Numeric Values (query line: 47): Referencing a numeric value (e.g. 1) as a string in a WHERE clause might result in poor performance. Possible impacts of storing numbers as varchars: more space will be used, you won't be able to perform arithmetic operations, the data won't be self-validated, aggregation functions like SUM won't work, the output may sort incorrectly and more. If the column is numeric, remove the quotes from the constant value, to make sure a numeric comparison is done.
9. Use UNION ALL instead of UNION (query line: 22): Always use UNION ALL unless you need to eliminate duplicate records. By using UNION ALL, you'll avoid the expensive distinct operation the database applies when using a UNION clause.

Optimal indexes for this query:

ALTER TABLE `mos_search_result_forcer` ADD INDEX `mos_result_idx_id` (`id`);
ALTER TABLE `node` ADD INDEX `node_idx_status` (`status`);
ALTER TABLE `search_dataset` ADD INDEX `search_dataset_idx_sid_type` (`sid`,`type`);
ALTER TABLE `search_index` ADD INDEX `search_index_idx_word_type` (`word`,`type`);
ALTER TABLE `search_total` ADD INDEX `search_total_idx_word` (`word`);

The optimized query:

SELECT
        i.type AS type,
        i.sid AS sid,
        SUM(CAST('10' AS DECIMAL) * COALESCE(((12.048628015788 * i.score * t.count)),
        0) / CAST('10' AS DECIMAL)) AS calculated_score 
    FROM
        (SELECT
            s.sid AS sid,
            s.word AS word,
            s.score AS score,
            s.type AS type 
        FROM
            search_index s 
        WHERE
            (
                s.word = 'turtles'
            ) 
            AND (
                s.type = 'node'
            ) 
        UNION
        SELECT
            m.nid AS sid,
            m.keyword AS word,
            (SELECT
                MAX(score) + m.id / (SELECT
                    MAX(mos_search_result_forcer.id) 
                FROM
                    mos_search_result_forcer) 
            FROM
                search_index) AS score,
                'node' AS type 
            FROM
                mos_search_result_forcer m) i 
        INNER JOIN
            node n 
                ON n.nid = i.sid 
        INNER JOIN
            search_total t 
                ON i.word = t.word 
        INNER JOIN
            search_dataset d 
                ON i.sid = d.sid 
                AND i.type = d.type 
        WHERE
            (
                n.status = '1'
            ) 
            AND (
                (
                    1 = 1
                )
            ) 
            AND (
                1 = 1
            ) 
            AND (
                (
                    d.data LIKE '% turtles %' ESCAPE '\\'
                )
            ) 
        GROUP BY
            d.type,
            d.sid 
        HAVING
            (
                COUNT(*) >= '1'
            ) 
        ORDER BY
            calculated_score DESC LIMIT 10 OFFSET 0