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如何优化ABAP性能

2011-12-09 10:03 267 查看
1、使用where语句
  不推荐

  Select * from zflight.

  Check : zflight-airln = ‘LF’ and zflight-fligh = ‘BW222’.

  Endselect.

  推荐

  Select * from zflight where airln = ‘LF’ and fligh = ‘222’.

  Endselect.

  2、使用聚合函数

  不推荐

  Maxnu = 0.

  Select * from zflight where airln = ‘LF’ and cntry = ‘IN’.

  Check zflight-fligh > maxnu.

  Maxnu = zflight-fligh.

  Endselect.

  推荐

  Select max( fligh ) from zflight into maxnu where airln = ‘LF’andcntry = ‘IN’.

  3、使用视图代替基本表查询

  不推荐

  Select * from zcntry where cntry like ‘IN%’.

  Select single * from zflight where cntry = zcntry-cntry andairln= ‘LF’.

  Endselect.

  推荐

  Select * from zcnfl where cntry like ‘IN%’ and airln = ‘LF’.

  Endselect.

  4、使用INTO table 代替select endselect

  不推荐

  Refresh: int_fligh.

  Select * from zflight into int_fligh.

  Append int_fligh. Clear int_fligh.

  Endselect.

  推荐

  Refresh: int_fligh.

  Select * from zflight into table int_fligh.

  5、使用批量修改内表代替逐行修改

  不推荐

  Loop at int_fligh.

  If int_fligh-flag is initial.

  Int_fligh-flag = ‘X’.

  Endif.

  Modify int_fligh.

  Endloop.

  推荐

  Int_fligh-flag = ‘X’.

  Modify int_fligh transporting flag where flag is initial.

  6、使用二分法查询,提高查询内表数据速度

  不推荐

  Read table int_fligh with key airln = ‘LF’.

  推荐

  Read table int_fligh with key airln = ‘LF’ binary search.

  7、两个内表添加使用批量增加代替逐行

  不推荐

  Loop at int_fligh1.

  Append int_fligh1 to int_fligh2.

  Endloop.

  推荐

  Append lines of int_fligh1 to int_fligh2.

  8、使用table buffering

  Use of buffered tables is recommended to improve theperformanceconsiderably. The buffer is bypassed while using thefollowingstatementsSelect distinct

  Select … for update

  Order by, group by, having clause

  Joins

  Use the Bypass buffer addition to the select clause in ordertoexplicitly bypass the buffer while selecting the data.

  9、 使用FOR ALL Entries

  不推荐

  Loop at int_cntry. Select single * from zfligh intoint_flighwhere cntry = int_cntry-cntry. Append int_fligh.Endloop.

  推荐

  Select * from zfligh appending table int_fligh

  For all entries in int_cntry

  Where cntry = int_cntry-cntry.

  10、正确地使用where语句,使查询能使用索引

  When a base table has multiple indices, the where clause shouldbein the order of the index, either a primary or a secondaryindex

  To choose an index, the optimizer checks the field namesspecifiedin the where clause and then uses an index that has thesame orderof the fields. One more tip is that if a table beginswith MANDT,while an index does not, there is a high possibilitythat theoptimizer
might not use that index.

  11、正确地使用MOVE语句

  Instead of using the move-corresponding clause it is advisabletouse the move statement instead. Attempt should be made tomoveentire internal table headers in a single shot, rather thanmovingthe fields one by one.

  12、正确地使用inner join

  Let us take an example of 2 tables, zairln and zflight. Thetablezairln has the field airln, which is the airline code and thefieldlnnam, which is the name of the airline. The table zflight hasthefield airln, the airline code and other fields which holdthedetails
of the flights that an airline operates.

  Since these 2 tables a re logically joined by the airln field,itis advisable to use the inner join.

  Select a~airln a~lnnam b~fligh b~cntry into table int_airdet

  From zairln as a inner join zflight as b on a~airln =b~airln.

  In order to restrict the data as per the selection criteria,awhere clause can be added to the above inner join.

  13、使用sort by 代替order by

  14、避免使用SELECT DISTINCT语句

  使用的 ABAP SORT + DELETE ADJACENT DUPLICATES 代替.
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