oracle – 插入到varchar2列中从xmltype列中选择：极慢

我使用的是oracle10gR2 10.2.0.4和solaris10 64bit

我需要从xmltype列表(word.testmeta)中的xml中选择数据值
并插入另一个表(word.testwordyy)

desc word.testmeta;
 Name                 Null?    Type
 --------------------------------------
 FILENAME             CHAR(2000)
 XMLDATA              XMLTYPE

desc word.testwordyy;
 Name                 Null?    Type
 ---------------------------------------
 ID                   VARCHAR2(255)
 KEYWORD              VARCHAR2(4000)

我使用xmltable并执行：

insert /*+append */ into word.testwordyy(KEYWORD)
select /*+ gather_plan_statistics */ dbms_lob.substr(xmltype.getclobval(b.KEWOR),254)
from word.testmeta,xmltable
(
'$B/mets/KEWOR'
passing
word.testmeta.XMLDATA as B
columns
KEWOR xmltype path '/KEWOR/text()'
)
b

这是解释计划select * from table(dbms_xplan.display_cursor(null,null,’iostats last’));

PLAN_TABLE_OUTPUT
-----------------------------------------------------------------------------------------------------------------------------------
SQL_ID  37ua3npnxx8su,child number 0
-------------------------------------
insert /*+append */ into word.testwordyy(KEYWORD) select /*+ gather_plan_statistics */
dbms_lob.substr(xmltype.getclobval(b.KEWOR),254) from word.testmeta,xmltable ( '$B/mets/KEWOR' passing
    > word.testmeta.XMLDATA as
B columns KEWOR xmltype path '/KEWOR/text()' ) b

Plan hash value: 875848213
-----------------------------------------------------------------------------------------------------------------------------------

PLAN_TABLE_OUTPUT
-----------------------------------------------------------------------------------------------------------------------------------
| Id  | Operation                           | Name                   | Starts | E-Rows | A-Rows |   A-Time   | Buffers | Reads  | Writes |
-----------------------------------------------------------------------------------------------------------------------------------
|   1 |  LOAD AS SELECT                     |                        |      1 |        |      1 |00:10:32.72 |   16832 |      7 |   90 |
|   2 |   NESTED LOOPS                      |                        |      1 |     29M|  34688 |00:00:25.95 |   12639 |      5 |    0 |
|   3 |    TABLE ACCESS FULL                | TESTMETA               |      1 |   3638 |   3999 |00:00:00.08 |     909 |      0 |    0 |
|   4 |    COLLECTION ITERATOR PICKLER FETCH| XMLSEQUENCEFROMXMLTYPE |   3999 |        |  34688 |00:00:24.50 |   11730 |      5 |    0 |

Note
-----
   - dynamic sampling used for this statement


21 rows selected.

表word.testmeta中的行数越多,每行花费的时间就越多

我的XML简单而小巧,但需要处理大量的XML(5000000)
当行数超过8000时,处理速度非常慢,需要几个小时.
有没有优化或更快的方式？

解决方法

“the contents of the tag are more than 4000 characters>>> are there any methods to substring the contents of the tag in the xmltable”

有XPath子串函数.

insert /*+append */ into word.testwordyy(KEYWORD)
select /*+ gather_plan_statistics */ b.KEWOR
from word.testmeta,xmltable
      (
        '$B/mets/KEWOR'
        passing
        word.testmeta.XMLDATA as B
        columns
        KEWOR varchar2(4000) path 'substring(KEWOR,254,4000)'
      ) b

在这里,我已经启动了您在原始帖子中使用的偏移量为254的子字符串.我还明确地将其长度设置为4000.

在声明列时,我认为您不需要显式引用text()节点.

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