申し訳ありませんが、ほぼすべての投稿とそれに関する質問を閲覧した後でも、単純なクエリで「一時的な使用」と「ファイルソートの使用」を取り除くことができません。これがキーの問題であることはわかっていますが、正しい組み合わせが見つかりません...
また、オプティマイザーによって定義された結合の順序が正しいかどうかもわかりません。STRAIGHT_JOIN を使用して他の順序をテストしましたが、それ以上のものはありませんでした。一時的な使用」と「ファイルソートの使用」！（ポイントテーブルには100.000行のようなものがあります）
クエリ:
SELECT points.id,
points.id_owner,
points.point_title,
points.point_desc,
users.user_id,
users.username
FROM points,
JOIN users ON points.id_owner = users.user_id
JOIN follows ON follows.id_followed = points.id_owner
WHERE points.deleted = 0
AND follows.id_follower = 22
ORDER BY points.id DESC
LIMIT 10
説明：
+----+-------------+---------+--------+---------------+------------+---------+---------------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+---------+--------+---------------+------------+---------+---------------------+------+----------------------------------------------+
| 1 | SIMPLE | follows | ref | FOLLOW_DUO | FOLLOW_DUO | 4 | const | 2 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | users | eq_ref | PRIMARY | PRIMARY | 4 | follows.id_followed | 1 | |
| 1 | SIMPLE | points | ref | GETPOINT1 | GETPOINT1 | 5 | users.user_id,const | 460 | Using where |
+----+-------------+---------+--------+---------------+------------+---------+---------------------+------+----------------------------------------------+
3 つのテーブルの SHOW INDEX は次のとおりです。
SHOW INDEX FROM points
+--------+------------+--------------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+--------+------------+--------------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+
| points | 0 | PRIMARY | 1 | id | A | 91987 | NULL | NULL | | BTREE | |
| points | 0 | GETPOINT1 | 1 | id_owner | A | NULL | NULL | NULL | | BTREE | |
| points | 0 | GETPOINT1 | 2 | deleted | A | NULL | NULL | NULL | | BTREE | |
| points | 0 | GETPOINT1 | 3 | id | A | 91987 | NULL | NULL | | BTREE | |
+--------+------------+--------------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+
SHOW INDEX FROM users
+-------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| users | 0 | PRIMARY | 1 | user_id | A | 4 | NULL | NULL | | BTREE | |
+-------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
SHOW INDEX FROM follows
+---------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+---------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| follows | 0 | PRIMARY | 1 | id | A | 5 | NULL | NULL | | BTREE | |
| follows | 0 | FOLLOW_DUO | 1 | id_follower | A | NULL | NULL | NULL | | BTREE | |
| follows | 0 | FOLLOW_DUO | 2 | id_followed | A | 5 | NULL | NULL | | BTREE | |
| follows | 1 | id_follower | 1 | id_follower | A | NULL | NULL | NULL | | BTREE | |
| follows | 1 | id_followed | 1 | id_followed | A | NULL | NULL | NULL | | BTREE | |
+---------+------------+-------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
これからは、「一時的な使用」と「ファイルソートの使用」を回避するために何をテストすればよいかわかりません...だから、私にアイデアがあれば...よろしくお願いします!