相关疑难解决方法(0)

使用PostgreSQL 8.4.9,我对查询的PostgreSQL性能有一个奇怪的问题.此查询正在选择3D卷中的一组点,使用a LEFT OUTER JOIN添加相关ID列,其中存在相关ID.x范围的微小变化可能导致PostgreSQL选择不同的查询计划,执行时间从0.01秒到50秒.这是有问题的查询:

SELECT treenode.id AS id,
       treenode.parent_id AS parentid,
       (treenode.location).x AS x,
       (treenode.location).y AS y,
       (treenode.location).z AS z,
       treenode.confidence AS confidence,
       treenode.user_id AS user_id,
       treenode.radius AS radius,
       ((treenode.location).z - 50) AS z_diff,
       treenode_class_instance.class_instance_id AS skeleton_id
  FROM treenode LEFT OUTER JOIN
         (treenode_class_instance INNER JOIN
          class_instance ON treenode_class_instance.class_instance_id
                                                  = class_instance.id
                            AND class_instance.class_id = 7828307)
       ON (treenode_class_instance.treenode_id = treenode.id
           AND treenode_class_instance.relation_id = 7828321)
  WHERE treenode.project_id = 4
    AND (treenode.location).x >= 8000
    AND (treenode.location).x <= (8000 + 4736) …