mariadb使用with子句改寫性能提高5倍

幾個月前，咱們有個產品的開發反饋了個問題，說有個組織結構的查詢很慢，幾千行的複雜關聯須要1秒鐘，表示太慢了，原語句以下：

SELECT
  org.org_id,
  org.dimension,
  org.org_code,
  org.org_name,
  org.parent_id,
  org.manage_id,
  org.org_cate,
  org.org_level,
  org.org_order,
  org.org_path,
  org.position_code,
  org.ext_id,
  org.remark,
  pos.position_name,
  parent.org_code AS parent_code,
  parent.org_name AS parent_name,
  manage.org_code AS manage_code,
  manage.org_name AS manage_name,
  org. STATUS
FROM
  tsys_organization org
LEFT JOIN tsys_position pos ON org.position_code = pos.position_code
LEFT JOIN tsys_organization parent ON org.parent_id = parent.org_id
LEFT JOIN tsys_organization manage ON org.manage_id = manage.org_id
WHERE 
  org.org_id IN(
    SELECT
      org.org_id
    FROM
      tsys_organization org
    JOIN tsys_user us ON us.user_id ='admin'
    
    UNION
      SELECT
        ou.org_id
      FROM
        tsys_org_user ou
      WHERE
        user_id ='admin'
      UNION
        SELECT
          org.org_id
        FROM
          tsys_organization org
        JOIN pos_user_view po ON po.user_id ='admin'
  )
AND org. STATUS = 0
ORDER BY
  org.org_order

夠複雜的，看了下執行計劃，確實有個子句沒有物化致使i/o訪問次數下不來，因而對該子查詢使用with重寫以下：

with a as (
    SELECT
      org2.org_id
    FROM
      tsys_organization org2
    JOIN tsys_user us ON us.user_id ='admin'
    
    UNION all
      SELECT
        ou.org_id
      FROM
        tsys_org_user ou
      WHERE
        user_id ='admin'
      UNION all
        SELECT
          org1.org_id
        FROM
          tsys_organization org1
        JOIN pos_user_view po ON po.user_id ='admin'
  )
SELECT
  org.org_id,
  org.dimension,
  org.org_code,
  org.org_name,
  org.parent_id,
  org.manage_id,
  org.org_cate,
  org.org_level,
  org.org_order,
  org.org_path,
  org.position_code,
  org.ext_id,
  org.remark,
  pos.position_name,
  parent.org_code AS parent_code,
  parent.org_name AS parent_name,
  manage.org_code AS manage_code,
  manage.org_name AS manage_name,
  org. STATUS
FROM
  tsys_organization org
LEFT JOIN tsys_position pos ON org.position_code = pos.position_code
LEFT JOIN tsys_organization parent ON org.parent_id = parent.org_id
LEFT JOIN tsys_organization manage ON org.manage_id = manage.org_id
WHERE 
  org.org_id IN (select org_id from a)
AND org. STATUS = 0
ORDER BY
  org.org_order

由於mariadb的with子句會強制物化爲臨時表，改寫後，0.2秒執行完成（oracle 12.2開始也支持強制，在此以前須要加materialized提示）。