无法在Postgresql中禁用订单连接

Question

Postgresql提供参数join_collapse_limit = 1来禁用连接顺序。但是当我设置参数并重置服务器时，查询计划不会更改，并且仍然存在订单连接优化。我的查询FROM表就像这样

FROM 
student as group_A, 
student as group_B,
student as group_C
WHERE ...

Answer 1

如果用户想要使用join_collapse_limit = 1来禁用连接重新排序，则必须在查询中提供显式JOINS。例如，上面的FROM表应该是

FROM 
student as group_A CROSS JOIN
student as group_B CROSS JOIN
student as group_C
WHERE ...