CASE ステートメント内でいくつかのサブクエリを使用する非常に複雑なクエリがあります。
この質問では、完全なクエリは必要なく、人々がすぐに問題に取り掛かるのを妨げるだけです。
したがって、この投稿では疑似コードを使用して作業します。必要に応じてクエリを投稿できますが、それは怪物であり、この質問には役に立ちません。
私が欲しいのは、CASE ステートメント内のキャッシュ可能なサブクエリです。
SELECT * FROM posts posts
INNER JOIN posts_shared_to shared_to
ON shared_to.post_id = posts.post_id
INNER JOIN channels.channels
ON channels.channel_id = shared_to.channel_id
WHERE posts.parent_id IS NULL
AND MATCH (post.text) AGAINST (:keyword IN BOOLEAN MODE)
AND CASE(
WHEN channel.read_access IS NULL THEN 1
WHEN channel.read_access = 1 THEN
(
SELECT count(*) FROM channel_users
WHERE user_id = XXX AND channel_id = channels.channel_id
)
WHEN shared_to.read_type = 2 THEN
(
/* another subquery with a join */
/* check if user is in friendlist of post_author */
)
ELSE 0
END;
)
GROUP BY post.post_id
ORDER BY post.post_id
DESC LIMIT n,n
上記のように、これは単純化された疑似コードにすぎません。
MySql EXPLAIN は、CASE 内で使用されるすべてのサブクエリが依存していることを示しています。これは、(私が正しければ) 毎回実行する必要があり、キャッシュされないことを意味します。
このクエリの高速化に役立つソリューションは大歓迎です。
編集部分: 真のクエリは次のようになります。
SELECT a.id, a.title, a.message AS post_text, a.type, a.date, a.author AS uid,
b.a_name as name, b.avatar,
shared_to.to_circle AS circle_id, shared_to.root_circle,
c.circle_name, c.read_access, c.owner_uid, c.profile,
MATCH(a.title,a.message) AGAINST (:keyword IN BOOLEAN MODE) AS score
FROM posts a
/** get userdetails for post_author **/
JOIN authors b ON b.id = a.author
/** get circles posts was shared to **/
JOIN posts_shared_to shared_to ON shared_to.post_id = a.id AND shared_to.deleted IS NULL
/**
* get circle_details note: at the moment shared_to can contain NULL and 1 too and doesnt need to be a circle_id
* if to_circle IS NULL post was shared public
* if to_circle = 1 post was shared to private circles
* since we use md5 keys as circle ids this can be a string insetad of (int) ... ugly..
*
**/
LEFT JOIN circles c ON c.circle_id = shared_to.to_circle
/*AND c.circle_name IS NOT NULL */
AND ( c.profile IS NULL OR c.profile = 6 OR c.profile = 1 )
AND c.deleted IS NULL
LEFT JOIN (
/** if post is within a channel that requires membership we use this to check if requesting user is member **/
SELECT COUNT(*) users_count, user_id, circle_id FROM circles_users
GROUP BY user_id, circle_id
) counts ON counts.circle_id = shared_to.to_circle
AND counts.user_id = :me
LEFT JOIN (
/** if post is shared private we check if requesting users exists within post authors private circles **/
SELECT count(*) in_circles_count, ci.owner_uid AS circle_owner, cu1.user_id AS user_me
FROM circles ci
INNER JOIN circles_users cu1 ON cu1.circle_id = ci.circle_id
AND cu1.deleted IS NULL
WHERE ci.profile IS NULL AND ci.deleted IS NULL
GROUP BY user_me, circle_owner
) users_in_circles ON users_in_circles.user_me = :me
AND users_in_circles.circle_owner = a.id
/** make sure post is a topic **/
WHERE a.parent_id IS NULL AND a.deleted IS NULL
/** search title and post body **/
AND MATCH (a.title,a.message) AGAINST (:keyword IN BOOLEAN MODE)
AND (
/** own circle **/
c.owner_uid = :me
/** site member read_access ( this query is for members, for guests we use a different query ) **/
OR ( c.read_access = 1 OR c.read_access = "1" )
/** public read_access **/
OR ( shared_to.to_circle IS NULL OR ( c.read_access IS NULL AND c.owner_uid IS NOT NULL ) )
/** channel/circle member read_access**/
OR ( c.read_access = 3 OR c.read_access = "3" AND counts.users_count > 0 )
/** for users within post creators private circles **/
OR (
(
/** use shared_to to determine if post is private **/
shared_to.to_circle = "1" OR shared_to.to_circle = 1
/** use circle settings to determine global privacy **/
OR ( c.owner_uid IS NOT NULL AND c.read_access = 2 OR c.read_access = "2" )
) AND users_in_circles.circle_owner = a.author AND users_in_circles.user_me = :me
)
)
GROUP BY a.id ORDER BY a.id DESC LIMIT n,n
質問: これは本当に良い方法ですか? 派生テーブルに含めることができる行数を見ると、よくわかりません。
そして、@ Ollie-Jones で言及されているように、誰かがクエリを変更するのを手伝ってくれるかもしれません:
SELECT stuff, stuff, stuff
FROM (
SELECT post.post_id
FROM your whole query
ORDER BY post_id DESC
LIMIT n,n
) ids
JOIN whatever ON whatever.post_id = ids.post_id
JOIN whatelse ON whatelse
これが怠惰に聞こえる場合は申し訳ありませんが、私は実際には mysqlguy ではなく、このクエリを作成するだけで何年も頭痛の種になりました。:D