为什么AUTOTRACE不会在执行计划中显示分区截断（partitionpruning）？

The(tm)Users'Co-OperativeFAQ
WhydoesAUTOTRACEnotshowpartitionpruningintheexplainplan?
为什么AUTOTRACE不会在执行计划中显示分区截断（partitionpruning）？
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Author'sname:NormanDunbar
作者：NormanDunbar
Author'sEmail:Oracle(at)BountifulSolutions.co.uk
Datewritten: 25 March2004
写作日期：2004年3月25日
Oracleversion(s):9.2.0.3.0
Oracle版本：9.2.0.3.0
WhyisitthatwhenIuseAUTOTRACEinSQL*Plus,theexplainplannevershowspartitionpruningtakingplace?
为什么当我在SQL*Plus中使用AUTOTRACE时，执行计划从不显示发生了分区截断呢？

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AUTOTRACEnotshowingpartitionpruning/eliminationisbug1426992,but,afterinvestigationOraclehasdecidedthatthisisnotanoptimiserbug,butabuginSQL*Plus.Youcan,withabitofknowledgeofyourdataandalittleexperimentation,deducethatpartitionpruningistakingplacefromtheoutputofAUTOTRACE,buttherearemucheasierways!
AUTOTRACE不显示分区截断/是错误（BUG）1426992，但调查后Oracle发现这不是优化器的错误，而是SQL*Plus的问题。对数据有所了解并经过一点试验后，你可以根据AUTOTRACE的输出推断出发生了分区截断，但有更简单的方法！
ThefollowingdemonstrationshowsthefailingsinAUTOTRACEanddemonstratesacoupleofothermethodsofdeterminingwhetherornotyourpartitionsarebeingpruned-ornot.
下面的演示显示了AUTOTRACE不能显示时用其他方法判断是否发生了分区截断。

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AUTOTRACE
AUTOTRACE
Firstofall,createasimpletablerangepartitionedover6differentpartitions,andfillitwithsometestdataextractedfromALL_OBJECTS.
首先创建一个简单的根据区间分为6个分区（rangepartitioned）的表，并从ALL_OBJECTS填充一些测试数据。

SQL>createtabletab_part(part_keynumber(1),some_textvarchar2(500))
2 partitionbyrange(part_key)(
3 partitionpart_1valueslessthan(2),
4 partitionpart_2valueslessthan(3),
5 partitionpart_3valueslessthan(4),
6 partitionpart_4valueslessthan(5),
7 partitionpart_5valueslessthan(6),
8 partitionpart_6valueslessthan(MAXVALUE));
Tablecreated.

SQL>insert/*+append*/intotab_part
2 selectmod(rownum,10),object_name
3 fromall_objects;
24683rowscreated.

SQL>commit;
Commitcomplete.
Oncethetablehasbeenfilled,analyseitandseehowthedatahasbeenspreadoverthevariouspartitions.Thefirstandlastpartitionshavemoredatainthemthattheremainingfour,hencethedifferingtotals.
一旦表中填入数据，分析并查看数据如何在不同的分区分布。第一和最后的分区比其他四个分区有更多的数据。

SQL>analyzetabletab_partcomputestatistics;
Tableanalyzed.

SQL>selectpartition_name,num_rows
2 fromuser_tab_partitions
3 wheretable_name='TAB_PART'1