[Solved] MySQL - LEFT JOIN doesn\'t return while CPU at 100%

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. 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.
  2. Sort and Limit Before Joining (modified query below): In cases where the joins aren't filtering any rows, it's possible to sort and limit the amount of rows using a subquery in the FROM clause, before applying the joins to all other tables.
Optimal indexes for this query:
ALTER TABLE `chat` ADD INDEX `chat_idx_id` (`id`);
The optimized query:
SELECT
        t1_id,
        t2.name,
        guid guid,
        t1_timestamp,
        t1_server_id,
        t1_message 
    FROM
        (SELECT
            t1.id AS t1_id,
            t1.name guid,
            t1.timestamp AS t1_timestamp,
            t1.server_id AS t1_server_id,
            t1.message AS t1_message 
        FROM
            chat t1 
        ORDER BY
            t1.id DESC LIMIT 20) t1 
    LEFT JOIN
        players t2 
            ON t2.guid = t1.guid LIMIT 20

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* original question posted on StackOverflow here.