Oracle SQL 优化：分层查询

Question

我有这个查询，它获取记录列表并跟踪每条记录的谱系，但它永远运行。谁能帮我提高性能？

  WITH root_nodes AS
  (SELECT distinct dlot.dim_lot_key AS lot_key, facility, lot
    FROM pedwroot.dim_lot dlot
    JOIN AT_LOT a
    ON (a.at_lot = dlot.lot AND a.at_facility = dlot.facility)
   WHERE (dlot.has_test_lpt = 'Y'
      or dlot.has_post_test_lpt = 'Y') and a.at_facility = 'MLA'),

    upstream_genealogy AS
    (SELECT /*+ INDEX(fact_link_lot IX_R_FLLOT_DLOT_2)*/DISTINCT CONNECT_BY_ROOT         
           fllot.dst_lot_key AS root_lot_key,
           fllot.src_lot_key
     FROM pedwroot.fact_link_lot fllot
     CONNECT BY NOCYCLE PRIOR fllot.src_lot_key = fllot.dst_lot_key
     START WITH fllot.dst_lot_key IN (SELECT lot_key FROM root_nodes)),

   at_lst AS
    (Select *
      FROM pedwroot.dim_lot dlot_lst
       JOIN upstream_genealogy upgen
        ON (upgen.src_lot_key = dlot_lst.dim_lot_key)
        where dlot_lst.has_assembly_lpt = 'Y')

      SELECT distinct dlot_root.lot         AS AT_LOT,
            dlot_root.facility    AS AT_FACILITY,
            dfac_root.common_name AS AT_SITE,
            dlot_root.LTC         AS AT_LTC,
            al.lot                AS AT_LST,
            dlot_src.lot          AS FAB_LOT,
            dlot_src.facility     AS FAB_FACILITY,
            dfac_src.common_name  AS FAB_SITE
       FROM upstream_genealogy upgen
       JOIN at_lst al
       ON (upgen.root_lot_key = al.root_lot_key)
       JOIN pedwroot.dim_lot dlot_src
       ON (upgen.src_lot_key = dlot_src.dim_lot_key)
       JOIN pedwroot.dim_lot dlot_root
       ON (upgen.root_lot_key = dlot_root.dim_lot_key)
       JOIN pedwroot.fact_lot flot
       ON (dlot_root.dim_lot_key = flot.lot_key)
       JOIN pedwroot.dim_facility dfac_root
       ON (flot.facility_key = dfac_root.dim_facility_key)
       JOIN pedwroot.dim_facility dfac_src
      ON (flot.fab_facility_key = dfac_src.dim_facility_key)
       WHERE dlot_src.has_fab_lpt = 'Y';

下面是这个查询的解释计划

Answer 1

基数从 1100 万突然变为 1 看起来是个问题。从查询中删除表和谓词，直到您准确找出导致该错误估计的原因。

大多数情况下，这些问题是由错误的统计信息引起的，请尝试收集所有相关表的统计信息。 （我能想到几十个其他潜在问题，但在你能把问题缩小一点之前，可能不值得猜测。）