SQL执行计划突变案例分析

前几日,同事发现一套库数据库的活动会话数激增,大量活动会话集中等待gc buffer busy acquire上,如下图所示

经过更一步的查看,发现这些等待均在sql_id:f7hnmtx8bd5q3上,利用如下sql进行查看发现:

SQL_TEXT如下:
SELECT *
FROM
  (SELECT p.*
   FROM t p,
        TD_PLAN_LEG d
   WHERE p.THR_DEP = d.THR_DEP
     AND p.THR_ARR = d.THR_ARR
     AND p.FLTNO = d._FLTNO
     AND pDATE = d.DATE
     AND (p.THR_DEP = :1
          OR p.THR_ARR = :2)
     AND nvl(d.STATUS_inner, ' ') != '??'
     AND d.LT_ID IS NULL
     AND nvl(d.STATUS_inner, ' ') != '??'
     AND p.OP_TM > :3
   ORDER BY p.OP_TM)
WHERE ROWNUM <= :4


SQL历史执行效率:
TIME      PLAN_HASH_VALUE EXECU_D        BG_D        DR_D      ET_D      CT_D IO_TIME CLUS_TIME AP_TIME CC_TIME GET_ONETIME   ROWS_PRO ROWS_ONETIME ET_MS_ONCE
------------ --------------- ------- ----------- ----------- --------- --------- ------- --------- ------- ------- ----------- ---------- ------------ ----------
2020092201        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092201        2495209816    3333  1351590946           0      2403      2409       0         0       0       0      405518        261            0        721
2020092202        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092202        2495209816    3238  1381884655           0      2449      2477       0         0       0       0      426771         82            0        756
2020092203        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092203        2495209816    3228  1380940555           0      2464      2475       0         0       0       0      427801         12            0        763
2020092204        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092204        2495209816    3249           0           0      2469      2486       0         0       0       0           0          0            0        760
2020092205        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092205        2495209816    3239  1401077673           0      2496      2510       0         0       0       0      432565          0            0        771
2020092206        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092206        2495209816    3240  1374013765           0      2449      2467       0         0       0       0      424078          0            0        756
2020092207        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092207        2495209816    3319           0           0      2584      2589       0         0       0       0           0        181            0        778
2020092208        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092208        2495209816    3656  1628720696           0      2827      2826       0         0       0       0      445493       1439            0        773
2020092209        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092209        2495209816    3238  1434887002           0      2610      2611       0         0       0       0      443140       2253            1        806
2020092210        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092210        2495209816    3240           0           0      2623      2629       0         0       0       0           0       2046            1        809
2020092211        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092211        2495209816    3240  1442329567           0      2672      2669       0         0       0       0      445163       2659            1        825
2020092212        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092212        2495209816    3240  1437033232           0      2676      2675       0         0       0       0      443529       2561            1        826
2020092213        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092213        2495209816    3222           0           0      2687      2689       0         0       0       0           0       2888            1        834
2020092214        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092214        2495209816    3240  1440743191           0      2706      2707       0         0       0       0      444674       3367            1        835
2020092215        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092215        2495209816    3243  1444795359           0      2747      2747       0         0       0       0      445512       2677            1        847
2020092216        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092216        2495209816    3243           0           0      2742      2749       0         0       0       0           0       2975            1        846
2020092217        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092217        2495209816    3256  1464276872           0      2774      2771       0         0       0       0      449716       2929            1        852
2020092218        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092218        2495209816    3240  1459846368           0      2802      2801       0         0       0       0      450570       3543            1        865
2020092219        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092219        2495209816    3240           0           0      2806      2806       0         0       0       0           0       3022            1        866
2020092220        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092220        2495209816    3221  1443354745           0      2819      2820       0         0       0       0      448108       2694            1        875
2020092221        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092221        2495209816    3239  1458055393           0      2891      2879       0         0       0       0      450156       2592            1        892
2020092222        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092222        2495209816    3240           0           0      2883      2887       0         0       0       0           0       2059            1        890
2020092223        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092223        2495209816    3240  1458681730           0      2926      2928       0         0       0       0      450210       1936            1        903
2020092300        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092300        2495209816    3238  1437599879           0      2925      2923       0         0       0       0      443978       1370            0        903
2020092301        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092301        2495209816    3251  1265725098           0      2330      2326       0         0       0       0      389334        695            0        717
2020092302        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092302        2495209816    3240  1322541308           0      2443      2447       0         0       0       0      408192        223            0        754
2020092303        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092303        2495209816    3240           0           0      2466      2471       0         0       0       0           0         41            0        761
2020092304        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092304        2495209816    3240  1309926437           0      2432      2431       0         0       0       0      404298          0            0        751
2020092305        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092305        2495209816    3250  1347086218           0      2466      2458       0         0       0       0      414488          0            0        759
2020092306        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092306        2495209816    3248  1327059467           0      2452      2452       0         0       0       0      408577          0            0        755
2020092307        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092307        2495209816    3242           0           0      2491      2488       0         0       0       0           0        194            0        768
2020092308        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092308        2495209816    3245  1405256862           0      2544      2538       0         0       0       0      433053       1625            1        784
2020092309        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092309        2495209816    3246  1421208667           0      2590      2579       0         0       0       0      437834       2518            1        798
2020092310        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092310        2495209816    3248           0           0      2619      2609       0         0       0       0           0       1961            1        806
2020092311        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092311        2495209816    3239  1426602319           0      2637      2632       0         0       0       0      440445       2673            1        814
2020092312        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092312        2495209816    3195  1403306564           0      2610      2603       0         0       0       0      439220       3029            1        817
2020092313        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092313        2495209816    3247           0           0      2698      2687       0         0       0       0           0       2976            1        831
2020092314        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092314        2495209816    3238  1418853144           0      2696      2690       0         0       0       0      438188       3496            1        833
2020092315        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092315        2495209816    3236  1443916772           0      2736      2728       0         0       0       0      446204       3600            1        846
2020092316        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092316        2495209816    3239           0           0      2731      2726       0         0       0       0           0       3630            1        843
2020092317        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092317        2495209816    3239  1435088513           0      2780      2768       0         0       0       0      443065       3446            1        858
2020092318        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092318        2495209816    3256  1422988985           0      2794      2782       0         0       0       0      437036       3043            1        858
2020092319        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092319        2495209816    3239           0           0      2816      2811       0         0       0       0           0       3108            1        869
2020092320        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092320        2495209816    3237  1414992685           0      2818      2813       0         0       0       0      437131       2993            1        870
2020092321        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092321        2495209816    3239  1450253448           0      2867      2859       0         0       0       0      447747       2686            1        885
2020092322        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092322        2495209816    3239           0           0      2866      2853       0         0       0       0           0       2661            1        885
2020092323        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092323        2495209816    3239  1440828417           0      2906      2889       0         0       0       0      444837       2007            1        897
2020092400        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092400        2495209816    3256  1405971757           0      2892      2884       0         0       0       0      431810       1569            0        888
2020092401        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092401        2495209816    3239   262264721           0      2332      2331       0         0       0       0       80971        570            0        720
2020092402        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092402        2495209816    3204  1328880815           0      2433      2428       0         0       0       0      414757        252            0        759
2020092403        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092403        2495209816    3240  1367144118           0      2459      2453       0         0       0       0      421958        101            0        759
2020092404        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092404        2495209816    3237  1318574101           0      2437      2432       0         0       0       0      407344         35            0        753
2020092405        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092405        2495209816    3220           0           0      2438      2435       0         0       0       0           0          0            0        757
2020092406        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092406        2495209816    3254  1346142138           0      2480      2469       0         0       0       0      413688          0            0        762
2020092407        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092407        2495209816    3238  1397020466           0      2503      2492       0         0       0       0      431445        160            0        773
2020092408        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092408        2495209816    3235           0           0      2529      2520       0         0       0       0           0       1401            0        782
2020092409        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092409        2495209816    3239  1424896212           0      2566      2556       0         0       0       0      439919       2275            1        792
2020092410        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092410        2495209816    3237  1421132007           0      2572      2569       0         0       0       0      439027       1956            1        795
2020092411        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092411        2495209816    3248           0           0      2629      2614       0         0       0       0           0       2913            1        809
2020092412        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092412        2495209816    3249  1448536971           0      2666      2651       0         0       0       0      445841       2722            1        820
2020092413        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092413        2495209816    3238  1437662381           0      2675      2668       0         0       0       0      443997       2445            1        826
2020092414        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092414        2495209816    3202           0           0      2680      2672       0         0       0       0           0       3238            1        837
2020092415        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092415        2495209816    3256  1450466091           0      2768      2758       0         0       0       0      445475       2920            1        850
2020092416        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092416        2495209816    3240  1450111226           0      2794      2779       0         0       0       0      447565       3109            1        862
2020092417        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092417        2495209816    3237           0           0      2824      2804       0         0       0       0           0       2818            1        873
2020092418        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092418        2495209816    3239  1424042026           0      2840      2831       0         0       0       0      439655       3346            1        877
2020092419        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092419        2495209816    3256  1435714284           0      2894      2885       0         0       0       0      440944       3120            1        889
2020092420        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092420        2495209816    3237           0           0      2914      2902       0         0       0       0           0       2788            1        900
2020092421        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092421        2495209816    3240  1433834204           0      2967      2946       0         0       0       0      442541       2857            1        916
2020092422        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092422        2495209816    3200  1413189546           0      2938      2924       0         0       0       0      441622       2346            1        918
2020092423        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092423        2495209816    3256           0           0      3032      3014       0         0       0       0           0       2108            1        931
2020092500        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092500        2495209816    3238  1417260989           0      3005      2982       0         0       0       0      437696       1358            0        928
2020092501        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092501        2495209816    3233  1296496694           0      2456      2444       0         0       0       0      401020        416            0        760
2020092502        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092502        2495209816    3220   473519624           0      2521      2518       0         0       0       0      147056        164            0        783
2020092503        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092503        2495209816    3257  1419336329           0      2546      2548       0         0       0       0      435780          9            0        782
2020092504        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092504        2495209816    3239  1410697902           0      2554      2548       0         0       0       0      435535          0            0        789
2020092505        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092505        2495209816    3239           0           0      2562      2548       0         0       0       0           0          0            0        791
2020092506        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092506        2495209816    3238  1422005253           0      2555      2551       0         0       0       0      439162          0            0        789
2020092507        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092507        2495209816    3244  1442245766           0      2591      2583       0         0       0       0      444589        276            0        799
2020092508        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092508        2495209816    3247           0           0      2642      2634       0         0       0       0           0       1679            1        814
2020092509        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092509        2495209816    3236  1467804298           0      2665      2656       0         0       0       0      453586       2599            1        824
2020092510        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092510        2495209816    3238  1462271228           0      2677      2670       0         0       0       0      451597       2009            1        827
2020092511        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092511        2495209816    3235           0           0      2720      2709       0         0       0       0           0       3010            1        841
2020092512        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092512        2495209816    3254  1465449842           0      2739      2723       0         0       0       0      450353       2555            1        842
2020092513        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092513        2495209816    3240  1459543406           0      2726      2709       0         0       0       0      450476       2664            1        841
2020092514        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092514        2495209816    3185           0           0      2702      2694       0         0       0       0           0       3784            1        848
2020092515        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092515        2495209816    3240  1447314954           0      2746      2742       0         0       0       0      446702       3116            1        848
2020092516        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092516        2495209816    3258  1475259620           0      2867      2821       0         0       0       0      452811       3183            1        880
2020092517        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092517        2495209816    3239           0           0      2841      2822       0         0       0       0           0       3168            1        877
2020092518        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092518        2495209816    3237  1455741217           0      2835      2815       0         0       0       0      449719       3258            1        876
2020092519        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092519        2495209816    3237  1456570263           0      2858      2846       0         0       0       0      449975       3135            1        883
2020092520        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092520        2495209816    3238           0           0      2881      2869       0         0       0       0           0       3033            1        890
2020092521        1636324798       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092521        2495209816    3238  1464946512           0      2912      2898       0         0       0       0      452423       2918            1        899
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2020092920        1636324798     198   725411011    42912011     66999      8657    8366     46635       0      72     3663692       4517           23     338377
2020092920        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092921        1636324798     182           0    56233403     68130      9001    9442     46655       0      79           0       3744           21     374340
2020092921        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092922        1636324798     200   761626806    56780398     67513      9089    8585     47243       0      60     3808134       3849           19     337564
2020092922        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020092923        1636324798     217   785661905    49927309     66720      9066    7530     46950       0      59     3620562       3528           16     307464
2020092923        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093000        1636324798     203   827248817    65561662     67630      9780    8513     46470       0      70     4075117       2246           11     333155
2020093000        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093001        1636324798     325  1200248776   124828228     62141     10674    6906     40984       0      19     3693073        619            2     191202
2020093001        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093002        1636324798     310  1110431303    39739255     57335      9643    2766     40456       0      23     3582036        185            1     184951
2020093002        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093003        1636324798     320  1149651569    39694801     61120      9942    3466     43492       0      27     3592661         47            0     191000
2020093003        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093004        1636324798     327           0    40854731     62249     10587    3609     43766       0      31           0         21            0     190365
2020093004        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093005        1636324798     319  1125342936    38863217     59590     10107    3507     41533       0      32     3527721          0            0     186801
2020093005        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093006        1636324798     309  1145849658    38889950     62572     10367    3745     44353       0      34     3708251          0            0     202500
2020093006        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093007        1636324798     327  1171387941    39245953     63327     10553    3852     44758       0      40     3582226        241            1     193662
2020093007        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093008        1636324798     296           0    38143234     64608     10248    4218     45887       0      41           0       2377            8     218271
2020093008        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093009        1636324798     291  1070234826    36419287     65024      9485    4331     46952       0      42     3677783       3606           12     223449
2020093009        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0
2020093010        1636324798     297  1060264318    35236356     65779      9293    4500     47678       0      43     3569914       3473           12     221476
2020093010        2495209816       0           0           0         0         0       0         0       0       0           0          0            0          0

404 rows selected.

从DBA_HIST_SQLSTAT中看到,该SQL有两个执行计划:

PLAH_HASH_VALUE:(1) 1636324798 (2)2495209816其中2495209816效率相对较高,1636324798一直存在但是在9月29日之前并没有启用过,一直在用2495209816,直到2020092902(2点)开始启用,并且在2020092903(3点)完全使用。但是ORACLE为何突然使用了差的执行计划了?


Inst: 1   Child: 0    Plan hash value: 2495209816

                      --------------------------------------------------------------------------------------------------------------------------------------------
                      | Id  | Operation                       | Name                         | E-Rows |E-Bytes| Cost (%CPU)| E-Time   |  OMem |  1Mem | Used-Mem |
                      --------------------------------------------------------------------------------------------------------------------------------------------
                      |   0 | SELECT STATEMENT                |                              |        |       |   372K(100)|          |       |       |          |
                      |*  1 |  COUNT STOPKEY                  |                              |        |       |            |          |       |       |          |
                      |   2 |   VIEW                          |                              |      1 |   176 |   372K  (1)| 01:14:32 |       |       |          |
                      |*  3 |    SORT ORDER BY STOPKEY        |                              |      1 |   125 |   372K  (1)| 01:14:32 |  1024 |  1024 |          |
                      |   4 |     NESTED LOOPS                |                              |      1 |   125 |   372K  (1)| 01:14:32 |       |       |          |
                      |   5 |      NESTED LOOPS               |                              |    120K|   125 |   372K  (1)| 01:14:32 |       |       |          |
                      |*  6 |       TABLE ACCESS FULL         | T1                           |    120K|  4482K| 10211   (1)| 00:02:03 |       |       |          |
                      |*  7 |       INDEX RANGE SCAN          | T_POSITIONS_KEY              |      1 |       |     3   (0)| 00:00:01 |       |       |          |
                      |*  8 |      TABLE ACCESS BY INDEX ROWID| T                            |      1 |    87 |     3   (0)| 00:00:01 |       |       |          |
                      --------------------------------------------------------------------------------------------------------------------------------------------

Inst: 1   Child: 38   Plan hash value: 1636324798

                      ----------------------------------------------------------------------------------------------------------------------------------
                      | Id  | Operation               | Name               | E-Rows |E-Bytes|E-Temp | Cost (%CPU)| E-Time   |  OMem |  1Mem | Used-Mem |
                      ----------------------------------------------------------------------------------------------------------------------------------
                      |   0 | SELECT STATEMENT        |                    |        |       |       |  1039K(100)|          |       |       |          |
                      |*  1 |  COUNT STOPKEY          |                    |        |       |       |            |          |       |       |          |
                      |   2 |   VIEW                  |                    |    118K|    19M|       |  1039K  (1)| 03:27:50 |       |       |          |
                      |*  3 |    SORT ORDER BY STOPKEY|                    |    118K|    14M|    16M|  1039K  (1)| 03:27:50 |  1024 |  1024 |          |
                      |*  4 |     HASH JOIN           |                    |    118K|    14M|  6024K|  1035K  (1)| 03:27:10 |  9516K|  3276K|   10M (0)|
                      |*  5 |      TABLE ACCESS FULL  | T1                 |    123K|  4576K|       | 10211   (1)| 00:02:03 |       |       |          |
                      |*  6 |      TABLE ACCESS FULL  | T                  |    118K|     9M|       |  1024K  (1)| 03:24:57 |       |       |          |
                      ----------------------------------------------------------------------------------------------------------------------------------

经过分析发现,此SQL涉及对象在9月28日时触发了统计信息收集,并且因此游标滚动失效,9月29日零时进行了硬解析。因数据库中绑定变量窥探关闭(_optim_peek_user_binds,被设定为FALSE),无法”窥视“直方图,根据数据分布与bind值分析,因数据倾斜严重+关闭“窥探直方图”情况下被认为平均分布,优化器选择了选择了”CBO认为效率高,实际效率差”的执行计划。针对此情形,可以利用SQL_PROFILE进行绑定(借助coe_load_sql_profile.sql)脚本绑定后

数据库GC类等待消失,SQL效率恢复至毫秒级别。