如何强制优化器重用 sql 游标
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【中文标题】如何强制优化器重用 sql 游标【英文标题】：How to force optimizer to reuse sql cursor 【发布时间】：2016-11-17 10:25:26 【问题描述】：我们在 oracle 12c 中遇到了 oracle 优化器的问题。它需要多次执行 sql 语句，直到 sql 被标记为 IS_REOPTIMIZABLE=N。
在 oracle11g/oracle12c 上输出相同的语句和几乎相同的数据。
-- output of v$sql (oracle 12c)
SQL_ID CHILD_NUMBER IS_REOPTIMIZABLE IS_BIND_SENSITIVE ELAPSED_TIME IS_BIND_AWARE IS_SHAREABLE IS_OBSOLETE FETCHES EXECUTIONS OPTIMIZER_COST SQL_PLAN_BASELINE
0f83zdknhqsmj 1 Y N 12575247 N N N 1 1 35 SQL_PLAN_3b0ugvyu8w97a4132b007
0f83zdknhqsmj 2 Y N 78337268 N N N 1 1 35 SQL_PLAN_3b0ugvyu8w97a4132b007
0f83zdknhqsmj 3 Y N 6079189 N N N 1 1 35 SQL_PLAN_3b0ugvyu8w97a4132b007
0f83zdknhqsmj 4 Y N 6162748 N N N 1 1 35 SQL_PLAN_3b0ugvyu8w97a4132b007
0f83zdknhqsmj 5 Y N 6647007 N N N 1 1 35 SQL_PLAN_3b0ugvyu8w97a4132b007
0f83zdknhqsmj 6 N N 6939813 N Y N 3 3 35 SQL_PLAN_3b0ugvyu8w97a4132b007
-- output of v$sql (oracle 11g)
SQL_ID CHILD_NUMBER IS_BIND_SENSITIVE ELAPSED_TIME IS_BIND_AWARE IS_SHAREABLE IS_OBSOLETE FETCHES EXECUTIONS OPTIMIZER_COST SQL_PLAN_BASELINE
0f83zdknhqsmj 0 N 2630792 N Y N 2 2 35 SQL_PLAN_3b0ugvyu8w97a4132b007
如你所见
经过时间在 oracle 12c 上非常糟糕。最后基线的执行计划总是被使用，这个计划已经足够好了。如果游标被重用（execution>=7），经过的时间大约是0.25秒
在 oracle 11g 上，游标立即被重用，在 oracle 12c 上，优化器需要 6 次尝试，直到它重用游标并且经过的时间可以接受。片刻之后，优化器重试优化 sql。
所以问题是： 我们并减少重新优化的工作量？
这里有一些可能需要的信息，如果您需要更多信息，请告诉我。 提前致谢！
-- optimization hints
select v.CHILD_NUMBER, v.HINT_ID, v.HINT_TEXT from V$SQL_REOPTIMIZATION_HINTS v where v.SQL_ID = '0f83zdknhqsmj';
CHILD_NUMBER HINT_ID HINT_TEXT
5 1 OPT_ESTIMATE (@"SEL$8" TABLE "HEFTFOLGE"@"SEL$8" MIN=132.000000 )
5 2 OPT_ESTIMATE (@"SEL$8" INDEX_FILTER "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=132.000000 )
5 3 OPT_ESTIMATE (@"SEL$8" INDEX_SCAN "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=132.000000 )
4 1 OPT_ESTIMATE (@"SEL$8" TABLE "HEFTFOLGE"@"SEL$8" MIN=578.000000 )
4 2 OPT_ESTIMATE (@"SEL$8" INDEX_FILTER "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=578.000000 )
4 3 OPT_ESTIMATE (@"SEL$8" INDEX_SCAN "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=578.000000 )
3 1 OPT_ESTIMATE (@"SEL$8" TABLE "HEFTFOLGE"@"SEL$8" MIN=75.000000 )
3 2 OPT_ESTIMATE (@"SEL$8" INDEX_FILTER "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=76.000000 )
3 3 OPT_ESTIMATE (@"SEL$8" INDEX_SCAN "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=76.000000 )
2 1 OPT_ESTIMATE (@"SEL$8" TABLE "HEFTFOLGE"@"SEL$8" MIN=730.000000 )
2 2 OPT_ESTIMATE (@"SEL$8" INDEX_FILTER "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=730.000000 )
2 3 OPT_ESTIMATE (@"SEL$8" INDEX_SCAN "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=730.000000 )
1 1 OPT_ESTIMATE (@"SEL$8" TABLE "HEFTFOLGE"@"SEL$8" MIN=1644.000000 )
1 2 OPT_ESTIMATE (@"SEL$8" INDEX_FILTER "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=1644.000000 )
1 3 OPT_ESTIMATE (@"SEL$8" INDEX_SCAN "HEFTFOLGE"@"SEL$8" "PS_CS_HEFTFOLGE_TB" MIN=1644.000000 )
-- Optimizer settings
NAME VALUE
plsql_optimize_level 2
optimizer_features_enable 12.1.0.2
optimizer_mode ALL_ROWS
_optimizer_max_permutations 50
optimizer_index_cost_adj 20
optimizer_index_caching 0
optimizer_dynamic_sampling 4
optimizer_secure_view_merging TRUE
optimizer_use_pending_statistics FALSE
optimizer_capture_sql_plan_baselines FALSE
optimizer_use_sql_plan_baselines TRUE
optimizer_use_invisible_indexes FALSE
optimizer_adaptive_reporting_only FALSE
optimizer_adaptive_features TRUE
optimizer_inmemory_aware TRUE
-- Execution plan
SQL_ID 0f83zdknhqsmj, child number 6
-------------------------------------
SELECT CS_AUFTRAG_ID, CS_AUFPOS_SEQ, CS_AUFLIEF_SEQ, CS_AUFUNT_SEQ,
CS_AUFUNT_SEQ_BEFR, CS_HEFTFOLGE_ID, SEQNO, CS_HEFTFOLGE,
TO_CHAR(ACTUAL_PUB_DATE,'YYYY-MM-DD'),
TO_CHAR(CS_VSSOLL_DT,'YYYY-MM-DD'), TO_CHAR(CS_VSIST_DT,'YYYY-MM-DD'),
CS_ANZAHL_GEL, CS_MINLIEF, CS_YESNO_WV, CS_YESNO_LIEFERN,
CS_BEFRIST_CD, CS_UNTERBR_CD, CS_UDGRUND_CD, CS_YESNO_LIEFEINST,
CS_VERSART_CD, CS_KONDITION, CS_LIEFERMENGE, CS_PREIS, CURRENCY_CD,
CS_YESNO_TERMADR, CS_KDNR_AS400, CS_ADR_LINE_1, CS_YESNO_NACHLIEF,
TO_CHAR(CS_VSIST2_DT,'YYYY-MM-DD'), CS_ZUSTELLTYP_CD, CS_YN_HORIZONT
FROM PS_CS_HEFTEREIT_VW WHERE CS_AUFTRAG_ID=:1 AND CS_AUFPOS_SEQ=:2 AND
CS_AUFLIEF_SEQ=:3 ORDER BY CS_AUFTRAG_ID, CS_AUFPOS_SEQ,
CS_AUFLIEF_SEQ, SEQNO
Plan hash value: 4191856942
-----------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 35 (100)| |
| 1 | SORT AGGREGATE | | 1 | 43 | | |
|* 2 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFLIEF_AU | 1 | 43 | 1 (0)| 00:00:01 |
|* 3 | INDEX RANGE SCAN | PSACS_AUFLIEF_AU | 1 | | 1 (0)| 00:00:01 |
| 4 | SORT ORDER BY | | 1 | 916 | 35 (9)| 00:00:01 |
|* 5 | FILTER | | | | | |
| 6 | NESTED LOOPS OUTER | | 1 | 916 | 31 (7)| 00:00:01 |
| 7 | NESTED LOOPS OUTER | | 1 | 866 | 30 (7)| 00:00:01 |
| 8 | NESTED LOOPS OUTER | | 1 | 798 | 29 (7)| 00:00:01 |
| 9 | NESTED LOOPS | | 1 | 708 | 28 (8)| 00:00:01 |
| 10 | NESTED LOOPS | | 1 | 640 | 27 (8)| 00:00:01 |
| 11 | NESTED LOOPS OUTER | | 1 | 550 | 26 (8)| 00:00:01 |
| 12 | NESTED LOOPS OUTER | | 1 | 512 | 25 (8)| 00:00:01 |
| 13 | NESTED LOOPS OUTER | | 1 | 469 | 24 (9)| 00:00:01 |
| 14 | NESTED LOOPS OUTER | | 1 | 411 | 23 (9)| 00:00:01 |
| 15 | VIEW | | 1 | 346 | 22 (10)| 00:00:01 |
| 16 | NESTED LOOPS OUTER | | 1 | 443 | 22 (10)| 00:00:01 |
|* 17 | VIEW | | 1 | 386 | 21 (10)| 00:00:01 |
| 18 | WINDOW SORT | | 1 | 540 | 21 (10)| 00:00:01 |
| 19 | NESTED LOOPS OUTER | | 1 | 540 | 20 (5)| 00:00:01 |
| 20 | NESTED LOOPS OUTER | | 1 | 488 | 19 (6)| 00:00:01 |
| 21 | NESTED LOOPS OUTER | | 1 | 424 | 18 (6)| 00:00:01 |
| 22 | NESTED LOOPS OUTER | | 1 | 374 | 17 (6)| 00:00:01 |
| 23 | NESTED LOOPS OUTER | | 1 | 322 | 16 (7)| 00:00:01 |
| 24 | VIEW | | 1 | 264 | 15 (7)| 00:00:01 |
| 25 | WINDOW BUFFER | | 1 | 254 | 15 (7)| 00:00:01 |
| 26 | VIEW | | 1 | 254 | 15 (7)| 00:00:01 |
| 27 | WINDOW SORT | | 1 | 532 | 15 (7)| 00:00:01 |
| 28 | NESTED LOOPS OUTER | | 1 | 532 | 13 (0)| 00:00:01 |
| 29 | NESTED LOOPS | | 1 | 503 | 12 (0)| 00:00:01 |
| 30 | NESTED LOOPS OUTER | | 1 | 474 | 11 (0)| 00:00:01 |
| 31 | NESTED LOOPS OUTER | | 1 | 445 | 10 (0)| 00:00:01 |
| 32 | NESTED LOOPS | | 1 | 390 | 9 (0)| 00:00:01 |
| 33 | NESTED LOOPS OUTER | | 1 | 303 | 8 (0)| 00:00:01 |
| 34 | NESTED LOOPS | | 1 | 258 | 7 (0)| 00:00:01 |
| 35 | NESTED LOOPS | | 1 | 240 | 6 (0)| 00:00:01 |
| 36 | NESTED LOOPS | | 1 | 198 | 5 (0)| 00:00:01 |
| 37 | NESTED LOOPS | | 1 | 171 | 4 (0)| 00:00:01 |
| 38 | VIEW | | 1 | 143 | 3 (0)| 00:00:01 |
| 39 | NESTED LOOPS | | 1 | 179 | 3 (0)| 00:00:01 |
| 40 | NESTED LOOPS | | 1 | 92 | 2 (0)| 00:00:01 |
| 41 | ROWID TABLE ACCESS BY INDEX | PS_CS_AUFTRAG_TB | 1 | 41 | 1 (0)| 00:00:01 |
|* 42 | INDEX UNIQUE SCAN | PS_CS_AUFTRAG_TB | 1 | | 1 (0)| 00:00:01 |
| 43 | ROWID TABLE ACCESS BY INDEX | PS_CS_AUFPOS_TB | 1 | 51 | 1 (0)| 00:00:01 |
|* 44 | INDEX UNIQUE SCAN | PS_CS_AUFPOS_TB | 1 | | 1 (0)| 00:00:01 |
| 45 | OWID TABLE ACCESS BY INDEX R | PS_CS_AUFLIEF_TB | 1 | 87 | 1 (0)| 00:00:01 |
|* 46 | INDEX UNIQUE SCAN | PS_CS_AUFLIEF_TB | 1 | | 1 (0)| 00:00:01 |
| 47 | ID TABLE ACCESS BY INDEX ROW | PS_CS_ARTIKEL_TB | 1 | 28 | 1 (0)| 00:00:01 |
|* 48 | INDEX UNIQUE SCAN | PS_CS_ARTIKEL_TB | 1 | | 1 (0)| 00:00:01 |
| 49 | D TABLE ACCESS BY INDEX ROWI | PS_CS_OBJEINW_TB | 1 | 27 | 1 (0)| 00:00:01 |
|* 50 | INDEX UNIQUE SCAN | PS_CS_OBJEINW_TB | 1 | | 1 (0)| 00:00:01 |
| 51 | TABLE ACCESS BY INDEX ROWID | PS_CS_MANDOBJ_TB | 1 | 42 | 1 (0)| 00:00:01 |
|* 52 | INDEX UNIQUE SCAN | PS_CS_MANDOBJ_TB | 1 | | 1 (0)| 00:00:01 |
| 53 | TABLE ACCESS BY INDEX ROWID | PS_CS_OBJSTEUER_TB | 1 | 18 | 1 (0)| 00:00:01 |
|* 54 | INDEX RANGE SCAN | PS_CS_OBJSTEUER_TB | 1 | | 1 (0)| 00:00:01 |
| 55 | SORT AGGREGATE | | 1 | 12 | | |
| 56 | FIRST ROW | | 1 | 12 | 1 (0)| 00:00:01 |
|* 57 | X) INDEX RANGE SCAN (MIN/MA | PS_CS_OBJSTEUER_TB | 1 | 12 | 1 (0)| 00:00:01 |
| 58 | TABLE ACCESS BY INDEX ROWID | PS_CS_AKT_PROD_TB | 1 | 45 | 1 (0)| 00:00:01 |
|* 59 | INDEX UNIQUE SCAN | PS_CS_AKT_PROD_TB | 1 | | 1 (0)| 00:00:01 |
|* 60 | TABLE ACCESS BY INDEX ROWID | PS_CS_HEFTFOLGE_TB | 6 | 522 | 1 (0)| 00:00:01 |
|* 61 | INDEX RANGE SCAN | PS_CS_HEFTFOLGE_TB | 2 | | 1 (0)| 00:00:01 |
| 62 | TABLE ACCESS BY INDEX ROWID | PS_CS_HEFTFOLGE_TB | 1 | 55 | 1 (0)| 00:00:01 |
|* 63 | INDEX UNIQUE SCAN | PS_CS_HEFTFOLGE_TB | 1 | | 1 (0)| 00:00:01 |
| 64 | TABLE ACCESS BY INDEX ROWID | PS_CS_HEFTFOLGE_TB | 1 | 29 | 1 (0)| 00:00:01 |
|* 65 | INDEX RANGE SCAN | PS0CS_HEFTFOLGE_TB | 1 | | 1 (0)| 00:00:01 |
| 66 | TABLE ACCESS BY INDEX ROWID | PS_CS_HEFTFOLGE_TB | 1 | 29 | 1 (0)| 00:00:01 |
|* 67 | INDEX RANGE SCAN | PS0CS_HEFTFOLGE_TB | 1 | | 1 (0)| 00:00:01 |
| 68 | TABLE ACCESS BY INDEX ROWID | PS_CS_HEFTFOLGE_TB | 1 | 29 | 1 (0)| 00:00:01 |
|* 69 | INDEX RANGE SCAN | PS0CS_HEFTFOLGE_TB | 1 | | 1 (0)| 00:00:01 |
|* 70 | TABLE ACCESS BY INDEX ROWID | PS_CS_SRY_REKLA_TB | 1 | 58 | 1 (0)| 00:00:01 |
|* 71 | INDEX RANGE SCAN | PSCCS_SRY_REKLA_TB | 1 | | 1 (0)| 00:00:01 |
|* 72 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFUNT_TB | 1 | 52 | 1 (0)| 00:00:01 |
|* 73 | INDEX RANGE SCAN | PS_CS_AUFUNT_TB | 1 | | 1 (0)| 00:00:01 |
|* 74 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFUNT_TB | 1 | 50 | 1 (0)| 00:00:01 |
|* 75 | INDEX RANGE SCAN | PS_CS_AUFUNT_TB | 1 | | 1 (0)| 00:00:01 |
|* 76 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFUNT_TB | 1 | 64 | 1 (0)| 00:00:01 |
|* 77 | INDEX RANGE SCAN | PS_CS_AUFUNT_TB | 1 | | 1 (0)| 00:00:01 |
|* 78 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFUNT_TB | 1 | 52 | 1 (0)| 00:00:01 |
|* 79 | INDEX RANGE SCAN | PS_CS_AUFUNT_TB | 1 | | 1 (0)| 00:00:01 |
|* 80 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFVERS_TB | 1 | 57 | 1 (0)| 00:00:01 |
|* 81 | INDEX RANGE SCAN | PS_CS_AUFVERS_TB | 2 | | 1 (0)| 00:00:01 |
| 82 | TABLE ACCESS BY INDEX ROWID | PS_CS_WVS_HFOLG_TB | 1 | 65 | 1 (0)| 00:00:01 |
|* 83 | INDEX UNIQUE SCAN | PS_CS_WVS_HFOLG_TB | 1 | | 1 (0)| 00:00:01 |
| 84 | TABLE ACCESS BY INDEX ROWID | PS_CS_VERSTRACK_TB | 1 | 58 | 1 (0)| 00:00:01 |
|* 85 | INDEX RANGE SCAN | PS1CS_VERSTRACK_TB | 1 | | 1 (0)| 00:00:01 |
|* 86 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFPOS_TB | 1 | 43 | 1 (0)| 00:00:01 |
|* 87 | INDEX RANGE SCAN | PSBCS_AUFPOS_TB | 1 | | 1 (0)| 00:00:01 |
| 88 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFLIEF_TB | 1 | 38 | 1 (0)| 00:00:01 |
|* 89 | INDEX RANGE SCAN | PS_CS_AUFLIEF_TB | 1 | | 1 (0)| 00:00:01 |
| 90 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFADR_TB | 1 | 90 | 1 (0)| 00:00:01 |
|* 91 | INDEX UNIQUE SCAN | PS_CS_AUFADR_TB | 1 | | 1 (0)| 00:00:01 |
| 92 | SORT AGGREGATE | | 1 | 49 | | |
|* 93 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFADR_TB | 1 | 49 | 1 (0)| 00:00:01 |
|* 94 | INDEX RANGE SCAN | PS_CS_AUFADR_TB | 1 | | 1 (0)| 00:00:01 |
| 95 | TABLE ACCESS BY INDEX ROWID | PS_CS_ADRART_TB | 1 | 68 | 1 (0)| 00:00:01 |
|* 96 | INDEX RANGE SCAN | PS_CS_ADRART_TB | 1 | | 1 (0)| 00:00:01 |
| 97 | SORT AGGREGATE | | 1 | 70 | | |
|* 98 | TABLE ACCESS BY INDEX ROWID | PS_CS_ADRART_TB | 1 | 70 | 1 (0)| 00:00:01 |
|* 99 | INDEX RANGE SCAN | PS_CS_ADRART_TB | 1 | | 1 (0)| 00:00:01 |
| 100 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFADR_TB | 1 | 90 | 1 (0)| 00:00:01 |
|*101 | INDEX RANGE SCAN | PS_CS_AUFADR_TB | 1 | | 1 (0)| 00:00:01 |
| 102 | TABLE ACCESS BY INDEX ROWID | PS_CS_ADRART_TB | 1 | 68 | 1 (0)| 00:00:01 |
|*103 | INDEX RANGE SCAN | PS_CS_ADRART_TB | 1 | | 1 (0)| 00:00:01 |
| 104 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFLIEFDT_TB | 1 | 50 | 1 (0)| 00:00:01 |
|*105 | INDEX RANGE SCAN | PS_CS_AUFLIEFDT_TB | 1 | | 1 (0)| 00:00:01 |
| 106 | SORT AGGREGATE | | 1 | 36 | | |
| 107 | FIRST ROW | | 1 | 36 | 1 (0)| 00:00:01 |
|*108 | INDEX RANGE SCAN (MIN/MAX) | PS_CS_AUFLIEFDT_TB | 1 | 36 | 1 (0)| 00:00:01 |
| 109 | SORT AGGREGATE | | 1 | 49 | | |
|*110 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFADR_TB | 1 | 49 | 1 (0)| 00:00:01 |
|*111 | INDEX RANGE SCAN | PS_CS_AUFADR_TB | 1 | | 1 (0)| 00:00:01 |
| 112 | SORT AGGREGATE | | 1 | 70 | | |
|*113 | TABLE ACCESS BY INDEX ROWID | PS_CS_ADRART_TB | 1 | 70 | 1 (0)| 00:00:01 |
|*114 | INDEX RANGE SCAN | PS_CS_ADRART_TB | 1 | | 1 (0)| 00:00:01 |
| 115 | SORT AGGREGATE | | 1 | 43 | | |
|*116 | FILTER | | | | | |
|*117 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFPOS_TB | 1 | 43 | 1 (0)| 00:00:01 |
|*118 | INDEX RANGE SCAN | PSBCS_AUFPOS_TB | 1 | | 1 (0)| 00:00:01 |
| 119 | SORT AGGREGATE | | 1 | 39 | | |
|*120 | TABLE ACCESS BY INDEX ROWID | PS_CS_AUFPOS_TB | 1 | 39 | 1 (0)| 00:00:01 |
|*121 | INDEX RANGE SCAN | PSBCS_AUFPOS_TB | 1 | | 1 (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------------------------------------------
Note
-----
- dynamic statistics used: dynamic sampling (level=4)
- SQL plan baseline SQL_PLAN_3b0ugvyu8w97a4132b007 used for this statement
- statistics feedback used for this statement
【问题讨论】：
优化器估计每个表只有 1 行。当你收集统计数据时它会改变吗？ 将 SQL 计划基线设置为 FIXED 是否有帮助？ 表PS_CS_HEFTFOLGE_TB 及其索引的统计信息是最新的。尽管如此，优化器估计“E-Rows=6”。有效结果为A-Rows=201。
不，将 SQL 计划基线设置为 FIXED 没有帮助。
【参考方案1】：
一般情况下，您可以运行以下 SQL：
select * from v$sql_shared_cursor
where sql_id = '0f83zdknhqsmj';
它会告诉你为什么 Oracle 不重用现有的子游标。
在您的特定情况下，您似乎已经知道不重用的原因是 Oracle 由于基数不匹配而重新优化查询，您可以直接进入此查询：
select *
from V$SQL_REOPTIMIZATION_HINTS
where sql_id = '0f83zdknhqsmj';
这应该让您深入了解基数不匹配涉及哪个计划步骤。
【讨论】：
谢谢，我已经检查了这些观点，你可以在我的问题末尾看到。问题是如何强制优化器立即使用基线 sql 重用现有游标。 你没有发布足够的信息让我在这里给你一个确凿的证据。我所能做的就是建议您使用该技术，即使用V$SQL_REOPTIMIZATION_HINTS 或alter session set statistics_level = ALL 加上DBMS_XPLAN.display_cursor 来确定Oracle 在其初始基数估计中出错的地方。然后，使用dbms_stats.create_extended_statistics 后跟dbms_stats.gather_table_stats 收集扩展（多列）统计信息，以便Oracle 的CBO 获得第一次做出正确基数估计所需的信息。
谢谢，我想我应该试试dbms_stats.create_extended_statistics。
祝你好运。为获得最佳结果，如果列中的数据有偏差，请务必使用直方图（使用 method_opt 参数）收集扩展统计信息。
这种方法是正确的，它有助于解决谓词引用同一个表的多个列的问题。以上是关于如何强制优化器重用 sql 游标的主要内容，如果未能解决你的问题，请参考以下文章
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