相关疑难解决方法(0)

我在视图中有一个非常大的查询（让我们称之为a_sql），这真的很快，除非我ORDER BY在SELECT带有小的外部使用LIMIT：

SELECT
customs.id AS custom_id, customs.custom_name AS custom_name, customs.slug AS slug, customs.use_case AS custom_use_case,
SUM(CASE WHEN designers.id = orders.user_id AND orders.bulk = 't' THEN order_rows.quantity ELSE 0 END) AS sale_bulk,
SUM(CASE WHEN designers.id = orders.user_id AND orders.bulk = 'f' THEN order_rows.quantity ELSE 0 END) AS sale_not_bulk,
SUM(CASE WHEN designers.id = orders.user_id THEN order_rows.quantity ELSE 0 END) AS sale_total,
SUM(CASE WHEN designers.id <> orders.user_id AND orders.bulk = 't' THEN order_rows.quantity ELSE 0 …

通常这样写很方便：

SELECT * 
FROM t1   # ... +many more tables
INNER JOIN t2 ON (t1.id = t2.col)
INNER JOIN t3 ON (t1.id = t3.col)
INNER JOIN t4 ON (t1.id = t4.col)
...

作为带条件的交叉连接：

SELECT * 
FROM t1, t2, t3, t4   # ... +many more tables
WHERE
       t1.id = t2.col
   AND t1.id = t3.col
   AND t1.id = t4.col
   # +include matches on columns of other tables

但是，交叉连接的简单实现将比内部连接具有更高的时间复杂度。Postgres 是否将第二个查询优化为与第一个查询具有相同时间复杂度的查询？