Jas*_*ker 1 oracle indexing sql-tuning
这是运行速度非常慢的查询的tkprof输出(警告:它很长:-)):
SELECT mbr_comment_idn, mbr_crt_dt, mbr_data_source, mbr_dol_bl_rmo_ind, mbr_dxcg_ctl_member, mbr_employment_start_dt, mbr_employment_term_dt, mbr_entity_active, mbr_ethnicity_idn, mbr_general_health_status_code, mbr_hand_dominant_code, mbr_hgt_feet, mbr_hgt_inches, mbr_highest_edu_level, mbr_insd_addr_idn, mbr_insd_alt_id, mbr_insd_name, mbr_insd_ssn_tin, mbr_is_smoker, mbr_is_vip, mbr_lmbr_first_name, mbr_lmbr_last_name, mbr_marital_status_cd, mbr_mbr_birth_dt, mbr_mbr_death_dt, mbr_mbr_expired, mbr_mbr_first_name, mbr_mbr_gender_cd, mbr_mbr_idn, mbr_mbr_ins_type, mbr_mbr_isreadonly, mbr_mbr_last_name, mbr_mbr_middle_name, mbr_mbr_name, mbr_mbr_status_idn, mbr_mpi_id, mbr_preferred_am_pm, mbr_preferred_time, mbr_prv_innetwork, mbr_rep_addr_idn, mbr_rep_name, mbr_rp_mbr_id, mbr_same_mbr_ins, mbr_special_needs_cd, mbr_timezone, mbr_upd_dt, mbr_user_idn, mbr_wgt, mbr_work_status_idn
FROM (SELECT /*+ FIRST_ROWS(1) */ mbr_comment_idn, mbr_crt_dt, mbr_data_source, mbr_dol_bl_rmo_ind, mbr_dxcg_ctl_member, mbr_employment_start_dt, mbr_employment_term_dt, mbr_entity_active, mbr_ethnicity_idn, mbr_general_health_status_code, mbr_hand_dominant_code, mbr_hgt_feet, mbr_hgt_inches, mbr_highest_edu_level, mbr_insd_addr_idn, mbr_insd_alt_id, mbr_insd_name, mbr_insd_ssn_tin, mbr_is_smoker, mbr_is_vip, mbr_lmbr_first_name, mbr_lmbr_last_name, mbr_marital_status_cd, mbr_mbr_birth_dt, mbr_mbr_death_dt, mbr_mbr_expired, mbr_mbr_first_name, mbr_mbr_gender_cd, mbr_mbr_idn, mbr_mbr_ins_type, mbr_mbr_isreadonly, mbr_mbr_last_name, mbr_mbr_middle_name, mbr_mbr_name, mbr_mbr_status_idn, mbr_mpi_id, mbr_preferred_am_pm, mbr_preferred_time, mbr_prv_innetwork, mbr_rep_addr_idn, mbr_rep_name, mbr_rp_mbr_id, mbr_same_mbr_ins, mbr_special_needs_cd, mbr_timezone, mbr_upd_dt, mbr_user_idn, mbr_wgt, mbr_work_status_idn, ROWNUM AS ora_rn
FROM (SELECT mbr.comment_idn AS mbr_comment_idn, mbr.crt_dt AS mbr_crt_dt, mbr.data_source AS mbr_data_source, mbr.dol_bl_rmo_ind AS mbr_dol_bl_rmo_ind, mbr.dxcg_ctl_member AS mbr_dxcg_ctl_member, mbr.employment_start_dt AS mbr_employment_start_dt, mbr.employment_term_dt AS mbr_employment_term_dt, mbr.entity_active AS mbr_entity_active, mbr.ethnicity_idn AS mbr_ethnicity_idn, mbr.general_health_status_code AS mbr_general_health_status_code, mbr.hand_dominant_code AS mbr_hand_dominant_code, mbr.hgt_feet AS mbr_hgt_feet, mbr.hgt_inches AS mbr_hgt_inches, mbr.highest_edu_level AS mbr_highest_edu_level, mbr.insd_addr_idn AS mbr_insd_addr_idn, mbr.insd_alt_id AS mbr_insd_alt_id, mbr.insd_name AS mbr_insd_name, mbr.insd_ssn_tin AS mbr_insd_ssn_tin, mbr.is_smoker AS mbr_is_smoker, mbr.is_vip AS mbr_is_vip, mbr.lmbr_first_name AS mbr_lmbr_first_name, mbr.lmbr_last_name AS mbr_lmbr_last_name, mbr.marital_status_cd AS mbr_marital_status_cd, mbr.mbr_birth_dt AS mbr_mbr_birth_dt, mbr.mbr_death_dt AS mbr_mbr_death_dt, mbr.mbr_expired AS mbr_mbr_expired, mbr.mbr_first_name AS mbr_mbr_first_name, mbr.mbr_gender_cd AS mbr_mbr_gender_cd, mbr.mbr_idn AS mbr_mbr_idn, mbr.mbr_ins_type AS mbr_mbr_ins_type, mbr.mbr_isreadonly AS mbr_mbr_isreadonly, mbr.mbr_last_name AS mbr_mbr_last_name, mbr.mbr_middle_name AS mbr_mbr_middle_name, mbr.mbr_name AS mbr_mbr_name, mbr.mbr_status_idn AS mbr_mbr_status_idn, mbr.mpi_id AS mbr_mpi_id, mbr.preferred_am_pm AS mbr_preferred_am_pm, mbr.preferred_time AS mbr_preferred_time, mbr.prv_innetwork AS mbr_prv_innetwork, mbr.rep_addr_idn AS mbr_rep_addr_idn, mbr.rep_name AS mbr_rep_name, mbr.rp_mbr_id AS mbr_rp_mbr_id, mbr.same_mbr_ins AS mbr_same_mbr_ins, mbr.special_needs_cd AS mbr_special_needs_cd, mbr.timezone AS mbr_timezone, mbr.upd_dt AS mbr_upd_dt, mbr.user_idn AS mbr_user_idn, mbr.wgt AS mbr_wgt, mbr.work_status_idn AS mbr_work_status_idn
FROM mbr JOIN mbr_identfn ON mbr.mbr_idn = mbr_identfn.mbr_idn
WHERE mbr_identfn.mbr_idn = mbr.mbr_idn AND mbr_identfn.identfd_type = :identfd_type_1 AND mbr_identfn.identfd_number = :identfd_number_1 AND mbr_identfn.entity_active = :entity_active_1)
WHERE ROWNUM <= :ROWNUM_1)
WHERE ora_rn > :ora_rn_1
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 9936 0.46 0.49 0 0 0 0
Execute 9936 0.60 0.59 0 0 0 0
Fetch 9936 329.87 404.00 0 136966922 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 29808 330.94 405.09 0 136966922 0 0
Misses in library cache during parse: 0
Optimizer mode: FIRST_ROWS
Parsing user id: 36 (JIVA_DEV)
Rows Row Source Operation
------- ---------------------------------------------------
0 VIEW (cr=102 pr=0 pw=0 time=2180 us)
0 COUNT STOPKEY (cr=102 pr=0 pw=0 time=2163 us)
0 NESTED LOOPS (cr=102 pr=0 pw=0 time=2152 us)
0 INDEX SKIP SCAN IDX_MBR_IDENTFN (cr=102 pr=0 pw=0 time=2140 us)(object id 341053)
0 TABLE ACCESS BY INDEX ROWID MBR (cr=0 pr=0 pw=0 time=0 us)
0 INDEX UNIQUE SCAN PK_CLAIMANT (cr=0 pr=0 pw=0 time=0 us)(object id 334044)
Rows Execution Plan
------- ---------------------------------------------------
0 SELECT STATEMENT MODE: HINT: FIRST_ROWS
0 VIEW
0 COUNT (STOPKEY)
0 NESTED LOOPS
0 INDEX MODE: ANALYZED (SKIP SCAN) OF 'IDX_MBR_IDENTFN'
(INDEX (UNIQUE))
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'MBR'
(TABLE)
0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PK_CLAIMANT'
(INDEX (UNIQUE))
********************************************************************************
根据我阅读Oracle的跳过扫描文档,当索引的第一列具有较少的唯一值时,跳过扫描最有用.问题是该列的第一个索引具有大量唯一身份.所以我认为跳过扫描是错误的做法是正确的吗？此外,什么样的扫描应该是可以做什么？我应该对此查询做一些暗示吗？
编辑:我还应该指出查询的where子句使用列,IDX_MBR_IDENTFN而不是该索引中的列.据我所知,我不会跳过任何专栏.
编辑2:我已经做了一些事情来加速这个查询.首先,我删除了分页.事实证明,此查询只返回一行.其次,我添加了一个LEADING提示,以确保以正确的顺序查询表.第三,我删除了重复的mbr_idn谓词.最后,我做了一个IDX_MBR_IDENTFN独特的.总而言之,这会大大提高性能(虽然它仍然是我运行的最昂贵的查询):
SELECT /*+ LEADING (mbr_identfn, mbr) */ mbr.comment_idn AS mbr_comment_idn, mbr.crt_dt AS mbr_crt_dt, mbr.data_source AS mbr_data_source, mbr.dol_bl_rmo_ind AS mbr_dol_bl_rmo_ind, mbr.dxcg_ctl_member AS mbr_dxcg_ctl_member, mbr.employment_start_dt AS mbr_employment_start_dt, mbr.employment_term_dt AS mbr_employment_term_dt, mbr.entity_active AS mbr_entity_active, mbr.ethnicity_idn AS mbr_ethnicity_idn, mbr.general_health_status_code AS mbr_general_health_status_code, mbr.hand_dominant_code AS mbr_hand_dominant_code, mbr.hgt_feet AS mbr_hgt_feet, mbr.hgt_inches AS mbr_hgt_inches, mbr.highest_edu_level AS mbr_highest_edu_level, mbr.insd_addr_idn AS mbr_insd_addr_idn, mbr.insd_alt_id AS mbr_insd_alt_id, mbr.insd_name AS mbr_insd_name, mbr.insd_ssn_tin AS mbr_insd_ssn_tin, mbr.is_smoker AS mbr_is_smoker, mbr.is_vip AS mbr_is_vip, mbr.lmbr_first_name AS mbr_lmbr_first_name, mbr.lmbr_last_name AS mbr_lmbr_last_name, mbr.marital_status_cd AS mbr_marital_status_cd, mbr.mbr_birth_dt AS mbr_mbr_birth_dt, mbr.mbr_death_dt AS mbr_mbr_death_dt, mbr.mbr_expired AS mbr_mbr_expired, mbr.mbr_first_name AS mbr_mbr_first_name, mbr.mbr_gender_cd AS mbr_mbr_gender_cd, mbr.mbr_idn AS mbr_mbr_idn, mbr.mbr_ins_type AS mbr_mbr_ins_type, mbr.mbr_isreadonly AS mbr_mbr_isreadonly, mbr.mbr_last_name AS mbr_mbr_last_name, mbr.mbr_middle_name AS mbr_mbr_middle_name, mbr.mbr_name AS mbr_mbr_name, mbr.mbr_status_idn AS mbr_mbr_status_idn, mbr.mpi_id AS mbr_mpi_id, mbr.preferred_am_pm AS mbr_preferred_am_pm, mbr.preferred_time AS mbr_preferred_time, mbr.prv_innetwork AS mbr_prv_innetwork, mbr.rep_addr_idn AS mbr_rep_addr_idn, mbr.rep_name AS mbr_rep_name, mbr.rp_mbr_id AS mbr_rp_mbr_id, mbr.same_mbr_ins AS mbr_same_mbr_ins, mbr.special_needs_cd AS mbr_special_needs_cd, mbr.timezone AS mbr_timezone, mbr.upd_dt AS mbr_upd_dt, mbr.user_idn AS mbr_user_idn, mbr.wgt AS mbr_wgt, mbr.work_status_idn AS mbr_work_status_idn
FROM mbr JOIN mbr_identfn ON mbr.mbr_idn = mbr_identfn.mbr_idn
WHERE mbr_identfn.identfd_type = :identfd_type_1 AND mbr_identfn.identfd_number = :identfd_number_1 AND mbr_identfn.entity_active = :entity_active_1
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 10102 0.45 0.42 0 0 0 0
Execute 10102 0.44 0.52 0 0 0 0
Fetch 10102 1.60 1.81 0 218121 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 30306 2.50 2.75 0 218121 0 0
Misses in library cache during parse: 0
Optimizer mode: ALL_ROWS
Parsing user id: 36 (JIVA_DEV)
Rows Row Source Operation
------- ---------------------------------------------------
0 NESTED LOOPS (cr=3 pr=0 pw=0 time=96 us)
0 TABLE ACCESS BY INDEX ROWID MBR_IDENTFN (cr=3 pr=0 pw=0 time=88 us)
0 INDEX UNIQUE SCAN UK_CLM_IDFN (cr=3 pr=0 pw=0 time=77 us)(object id 334118)
0 TABLE ACCESS BY INDEX ROWID MBR (cr=0 pr=0 pw=0 time=0 us)
0 INDEX UNIQUE SCAN PK_CLAIMANT (cr=0 pr=0 pw=0 time=0 us)(object id 334044)
Rows Execution Plan
------- ---------------------------------------------------
0 SELECT STATEMENT MODE: ALL_ROWS
0 NESTED LOOPS
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF
'MBR_IDENTFN' (TABLE)
0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'UK_CLM_IDFN' (INDEX
(UNIQUE))
0 TABLE ACCESS MODE: ANALYZED (BY INDEX ROWID) OF 'MBR' (TABLE)
0 INDEX MODE: ANALYZED (UNIQUE SCAN) OF 'PK_CLAIMANT' (INDEX
(UNIQUE))
索引跳过扫描意味着忽略索引的第一列.由于Oracle已读取第一列的每个项目,并检查第二列(或第三列,...)列是否为您搜索的内容,因此会降低性能.这通常比全表扫描(取决于您的查询)更快,但比索引范围扫描慢.
尝试在列中创建单独的索引,该列是IDX_MBR_IDENTFN查询的一部分并在查询中使用.
例如,如果your_table看起来像这样:
id status
1 0
2 0
3 0
4 1
并且你有一个复合索引(id, status),查询Select * From your_table Where status = 1很可能使用索引,但为了找到正确的行,它必须读取索引的每一行(id 1to 4)并检查status.
更新:以下索引可以进一步提高性能,但您必须尝试它是否真的有帮助:
mbr_identfn( identfd_type, identfd_number, entity_active, mbr_idn )
这甚至可以帮助避免暗示.
我会把注意力从跳过扫描转移开.
tkprof代码段显示您的首要任务应该是减少发出此语句的次数.目前您执行此语句9936次.每次执行只需要405/9936秒.合理快速.但如果执行9936次则不行.
所以这个陈述几乎可以肯定在循环结构中.在每次迭代中,您提供不同的输入参数集(:identfd_type_1,:identfd_number_1,:entity_active_1,:ROWNUM_1,:ora_rn_1).重写此循环结构以使此语句对整个集合执行一次,并且您的性能问题可能是过去的事情.如果没有,请发布新的tkprof输出.
问候,Rob.
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