Question

我遇到了一个我很难理解的问题。我有两个运行缓慢的查询。所以我开始研究性能问题。两个查询中的所有表都有最近更新的统计信息，因此当我使用/ * + gather_plan_statistics * /提示运行两个查询时，当我使用下面的视图查看实际统计数据时，我感到非常惊讶。

    select * from table(dbms_xplan.display_cursor(null, null, 'ALLSTATS LAST'));

解释计划的估计行数和实际行数之间存在很大差异。 可能的原因是什么？如果表统计数据是最新的，为什么会有很大差异？我可以开始使用提示，但我宁愿让优化器。

我已经包含了SQL查询并解释了下面的计划。

select /*+ ORDERED USE_NL(prod,tle,uh,bro) gather_plan_statistics */  
      prod.cre_surr_id, 
      tle.title , 
      min(uh.performance_date)     performance_date, 
      prod.year_of_production, 
      prod.production_type  type_code 
from   wacsusers.prod_date_constraint_vw pdcv join prblk.productions  prod ON prod.cre_surr_id = pdcv.cre_surr_id 
   inner join titles tle on tle.cre_surr_id = prod.cre_surr_id and tle.tt_code = 'R' 
   left join prblk.usage_headers uh on uh.prod_exploitation_cre_surr_id = prod.cre_surr_id 
   left join broadcasters bro on bro.tp_surr_id = uh.bro_broadcast_by_tp_surr_id 
 where  pdcv.title like 'BELIEVE%'  and uh.performance_date between to_date('01-JAN-1900','DD-MON-YYYY') and to_date('01-JAN-2900','DD-MON-YYYY')
  AND    prod.dn_prst_status = '4'  
  AND    prod.medium_type = 'AV' 
  group by prod.cre_surr_id, 
        prod.production_type, 
        tle.title, 
        prod.year_of_production, 
        prod.music_content_indicator 
HAVING   (prod.music_content_indicator IN ('Y', 'N') 
  OR prod.music_content_indicator IS NULL 
  OR (prod.music_content_indicator = 'W' 
  AND (prod.production_type = 'COM' 
  AND MIN (uh.performance_date) BETWEEN (SYSDATE - 1091) AND (SYSDATE - 90)) 
  OR (prod.production_type != 'COM' AND MIN (uh.performance_date) 
  BETWEEN (SYSDATE - 1091) AND (SYSDATE - 90)))) order by title asc

  1 - filter(("PROD"."MUSIC_CONTENT_INDICATOR"='Y' OR "PROD"."MUSIC_CONTENT_INDICATOR"='N' OR "PROD"."MUSIC_CONTENT_INDICATOR" IS NULL OR 
          ("PROD"."MUSIC_CONTENT_INDICATOR"='W' AND "PROD"."PRODUCTION_TYPE"='COM' AND MIN("UH"."PERFORMANCE_DATE")>=SYSDATE@!-1091 AND 
          MIN("UH"."PERFORMANCE_DATE")<=SYSDATE@!-90) OR ("PROD"."PRODUCTION_TYPE"<>'COM' AND MIN("UH"."PERFORMANCE_DATE")>=SYSDATE@!-1091 AND 
          MIN("UH"."PERFORMANCE_DATE")<=SYSDATE@!-90)))
   7 - filter(("PTM"."MUSIC_CONTENT_INDICATOR" IS NULL OR "PTM"."MUSIC_CONTENT_INDICATOR"="CONSTANTS"."CONTENT_YES"() OR 
          "PTM"."MUSIC_CONTENT_INDICATOR"="CONSTANTS"."CONTENT_NO"() OR ("PTM"."START_DTM">=SYSDATE@!-"CONSTANTS"."FLICS_INC_STA_DYS_AGO"() AND 
          "PTM"."START_DTM"<=SYSDATE@!-"CONSTANTS"."FLICS_INC_END_DYS_AGO"() AND "PTM"."PRODUCTION_TYPE"<>"CONSTANTS"."PROD_TYPE_COMMERCIAL"()) OR 
          ("PTM"."START_DTM">=SYSDATE@!-"CONSTANTS"."CLICS_INC_STA_DYS_AGO"() AND "PTM"."START_DTM"<=SYSDATE@!-"CONSTANTS"."CLICS_INC_END_DYS_AGO"() AND 
          "PTM"."PRODUCTION_TYPE"="CONSTANTS"."PROD_TYPE_COMMERCIAL"() AND "PTM"."MUSIC_CONTENT_INDICATOR"="CONSTANTS"."CONTENT_WAITING"())))
   8 - access("PTM"."TITLE" LIKE 'BELIEVE%')
   filter("PTM"."TITLE" LIKE 'BELIEVE%')
   9 - filter(("PROD"."DN_PRST_STATUS"='4' AND "PROD"."MEDIUM_TYPE"='AV'))
  10 - access("PROD"."CRE_SURR_ID"="PTM"."CRE_SURR_ID")
  12 - access("TLE"."CRE_SURR_ID"="PROD"."CRE_SURR_ID" AND "TLE"."TT_CODE"='R')
  13 - access("UH"."PROD_EXPLOITATION_CRE_SURR_ID"="PROD"."CRE_SURR_ID")
   filter("UH"."PROD_EXPLOITATION_CRE_SURR_ID" IS NOT NULL)
  14 - filter(("UH"."PERFORMANCE_DATE">=TO_DATE(' 1900-01-01 00:00:00', 'syyyy-mm-dd hh24:mi:ss') AND "UH"."PERFORMANCE_DATE"<=TO_DATE(' 2900-01-01 
          00:00:00', 'syyyy-mm-dd hh24:mi:ss')))

-

SELECT   /*+ gather_plan_statistics */  prod.cre_surr_id, 
       tle.title, prod.year_of_production, 
       prod.music_content_indicator 
 FROM     prblk.productions prod 
     INNER JOIN titles tle ON tle.cre_surr_id = prod.cre_surr_id AND tle.tt_code = 'R' 
        JOIN  (SELECT DISTINCT cc.prod_cre_surr_id 
               FROM   prblk.creation_components cc
               INNER JOIN works wrk  ON wrk.cre_surr_id = cc.wrk_cre_surr_id 
               WHERE  wrk.logically_deleted_y IS NULL 
               AND EXISTS   ( SELECT  1 
                           FROM   tle_title_tokens ttt  
                           WHERE token_type in ('E', 'N')  
                           AND dn_wrk_cre_surr_id = wrk.cre_surr_id  
                           AND  search_token LIKE :title||'%' )                                          
               AND EXISTS ( SELECT 1  
                           FROM   works_ips wips,  
                                ip_name_tokens ipnt  
                           WHERE  wips.ip_surr_id = ipnt.ip_surr_id  
                           AND    ipnt.search_token like :writer||'%'  
                           AND ipnt.token_type = 'N'  
                           AND wips.wrk_cre_surr_id = wrk.cre_surr_id)  
            AND cc.dn_ccst_status <> '6' ) cct ON cct.prod_cre_surr_id = prod.cre_surr_id  
            AND (( prod.music_content_indicator = 'W'  
            AND (SELECT MIN (uh.performance_date) 
                 FROM   prblk.usage_headers uh 
                 WHERE  uh.prod_exploitation_cre_surr_id = prod.cre_surr_id) BETWEEN SYSDATE -  CASE prod.production_type WHEN 'COM'                                                                                                         THEN 1091 
                                                                                                      ELSE 1091                                                                                                     END 
                   AND SYSDATE -  CASE prod.production_type WHEN 'COM' 
                                           THEN 90 
                                           ELSE 90 
                                END    ) OR NVL  (prod.music_content_indicator, 'N') in ('Y','N') ) ORDER BY title asc

 Predicate Information (identified by operation id):
 ---------------------------------------------------

  2 - filter((NVL("SYS_ALIAS_1"."MUSIC_CONTENT_INDICATOR",'N')='Y' OR NVL("SYS_ALIAS_1"."MUSIC_CONTENT_INDICATOR",'N')='N' OR 
          ("SYS_ALIAS_1"."MUSIC_CONTENT_INDICATOR"='W' AND >=SYSDATE@!-1091 AND <=SYSDATE@!-90)))
  5 - access("CCT"."PROD_CRE_SURR_ID"="SYS_ALIAS_1"."CRE_SURR_ID")
  8 - access("WRK"."CRE_SURR_ID"="CC"."WRK_CRE_SURR_ID")
  9 - access("TTT"."DN_WRK_CRE_SURR_ID"="WRK"."CRE_SURR_ID")
 10 - access("WIPS"."WRK_CRE_SURR_ID"="WRK"."CRE_SURR_ID")
 11 - filter("WRK"."LOGICALLY_DELETED_Y" IS NULL)
 12 - access("WIPS"."IP_SURR_ID"="IPNT"."IP_SURR_ID")
 13 - access("IPNT"."TOKEN_TYPE"='N' AND "IPNT"."SEARCH_TOKEN" LIKE :WRITER||'%')
   filter("IPNT"."SEARCH_TOKEN" LIKE :WRITER||'%')
 16 - access((("TTT"."TOKEN_TYPE"='E' OR "TTT"."TOKEN_TYPE"='N')) AND "TTT"."SEARCH_TOKEN" LIKE :TITLE||'%')
   filter("TTT"."SEARCH_TOKEN" LIKE :TITLE||'%')
 17 - filter(("CC"."WRK_CRE_SURR_ID" IS NOT NULL AND "CC"."DN_CCST_STATUS"<>'6'))
 19 - access("TLE"."CRE_SURR_ID"="SYS_ALIAS_1"."CRE_SURR_ID" AND "TLE"."TT_CODE"='R')
 23 - access("UH"."PROD_EXPLOITATION_CRE_SURR_ID"=:B1)

Oracle SQL查询 - 解释计划大的估计/实际行差异

0 个答案: