01-24-2008 2:39 PM
Hi friends
I am writing below code
loop at tab1.
select single * from tablename
where objnr = tab1-field.
if sy-subrc = 0.
delete tab1.
continue.
else.
perform sleset.
endif.
endloop.
select inside the loop statement, This will raise performance issue. pls let me know how to rewrite the code without effecting the performance
thanks
01-24-2008 2:46 PM
Press F1 on SELECT and look at the section on FOR ALL ENTRIES.
Rob
01-25-2008 4:26 AM
Hi karthik,
Put the select statement before the loop for all entries in tab1.
Now inside the loop use Read statement for objnr = tab1-field.
This will solve your problem.
Reward Points if Helpful.
Regards,
Sachin M M
01-25-2008 4:39 AM
Hi,
sort the internal table tab1 by field.
change the existing query to this :
if not tab1[] is initial.
select * from tablename into tab2
for all entries in tab1
where objnr = tab1-field.
if sy-subrc ne 0.
do the action which you want to take
endif.
endif.
Now your tab2 will contain only those entries which are present in tablename.
If you want to delete the entries from tab1 which are not present in tab2 then
sort tb_tab2 by field.
loop at tab1.
read table tab with key field = tab1-field binary search transporting no fields.
sy-subrc ne 0.
delete tab1.
endif.
endloop.
Hope this helps you!!
Thanks and Regards,
Sriranjani Chimakurthy.
01-25-2008 9:18 AM
Sorry, there is not automatically a performance issue if there is SELECT SINGLE inside a LOOP.
Usually it is o.k.
You should only change the coding, if the internal table tab1 and the database table for the SELECT are very large and the whole this is really performance crictical.
But if you change then you should really know what you doing.
The FOR ALL ENTRIES does not require a sorted table tab1.
Instead of the SELECT SINGLE there must be READ inside the LOOP the READ must at least be a READ BINARY SEARCH better a HASHED READ.
For performance optimization of existing coding I would always recommend you to run trace
(SE30 and ST05) and concentrate on the top contributions.
I would wonder there are no other issues, with much more potential.
Siegfried
01-25-2008 12:07 PM
AVOID LOOP AND WRITE THE READ CONDITION IT WILL IMPROVE THE PERFORMANCE
01-25-2008 12:07 PM
Ways of Performance Tuning
1. Selection Criteria
2. Select Statements
Select Queries
SQL Interface
Aggregate Functions
For all Entries
Select Over more than one internal table
Selection Criteria
1. Restrict the data to the selection criteria itself, rather than filtering it out using the ABAP code using CHECK statement.
2. Select with selection list.
SELECT * FROM SBOOK INTO SBOOK_WA.
CHECK: SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
ENDSELECT.
The above code can be much more optimized by the code written below which avoids CHECK, selects with selection list
SELECT CARRID CONNID FLDATE BOOKID FROM SBOOK INTO TABLE T_SBOOK
WHERE SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
Select Statements Select Queries
1. Avoid nested selects
SELECT * FROM EKKO INTO EKKO_WA.
SELECT * FROM EKAN INTO EKAN_WA
WHERE EBELN = EKKO_WA-EBELN.
ENDSELECT.
ENDSELECT.
The above code can be much more optimized by the code written below.
SELECT PF1 PF2 FF3 FF4 INTO TABLE ITAB
FROM EKKO AS P INNER JOIN EKAN AS F
ON PEBELN = FEBELN.
Note: A simple SELECT loop is a single database access whose result is passed to the ABAP program line by line. Nested SELECT loops mean that the number of accesses in the inner loop is multiplied by the number of accesses in the outer loop. One should therefore use nested SELECT loops only if the selection in the outer loop contains very few lines or the outer loop is a SELECT SINGLE statement.
2. Select all the records in a single shot using into table clause of select statement rather than to use Append statements.
SELECT * FROM SBOOK INTO SBOOK_WA.
CHECK: SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
ENDSELECT.
The above code can be much more optimized by the code written below which avoids CHECK, selects with selection list and puts the data in one shot using into table
SELECT CARRID CONNID FLDATE BOOKID FROM SBOOK INTO TABLE T_SBOOK
WHERE SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
3. When a base table has multiple indices, the where clause should be in the order of the index, either a primary or a secondary index.
To choose an index, the optimizer checks the field names specified in the where clause and then uses an index that has the same order of the fields. In certain scenarios, it is advisable to check whether a new index can speed up the performance of a program. This will come handy in programs that access data from the finance tables.
4. For testing existence, use Select.. Up to 1 rows statement instead of a Select-Endselect-loop with an Exit.
SELECT * FROM SBOOK INTO SBOOK_WA
UP TO 1 ROWS
WHERE CARRID = 'LH'.
ENDSELECT.
The above code is more optimized as compared to the code mentioned below for testing existence of a record.
SELECT * FROM SBOOK INTO SBOOK_WA
WHERE CARRID = 'LH'.
EXIT.
ENDSELECT.
5. Use Select Single if all primary key fields are supplied in the Where condition .
If all primary key fields are supplied in the Where conditions you can even use Select Single.
Select Single requires one communication with the database system, whereas Select-Endselect needs two.
Select Statements SQL Interface
1. Use column updates instead of single-row updates
to update your database tables.
SELECT * FROM SFLIGHT INTO SFLIGHT_WA.
SFLIGHT_WA-SEATSOCC =
SFLIGHT_WA-SEATSOCC - 1.
UPDATE SFLIGHT FROM SFLIGHT_WA.
ENDSELECT.
The above mentioned code can be more optimized by using the following code
UPDATE SFLIGHT
SET SEATSOCC = SEATSOCC - 1.
2. For all frequently used Select statements, try to use an index.
SELECT * FROM SBOOK CLIENT SPECIFIED INTO SBOOK_WA
WHERE CARRID = 'LH'
AND CONNID = '0400'.
ENDSELECT.
The above mentioned code can be more optimized by using the following code
SELECT * FROM SBOOK CLIENT SPECIFIED INTO SBOOK_WA
WHERE MANDT IN ( SELECT MANDT FROM T000 )
AND CARRID = 'LH'
AND CONNID = '0400'.
ENDSELECT.
3. Using buffered tables improves the performance considerably.
Bypassing the buffer increases the network considerably
SELECT SINGLE * FROM T100 INTO T100_WA
BYPASSING BUFFER
WHERE SPRSL = 'D'
AND ARBGB = '00'
AND MSGNR = '999'.
The above mentioned code can be more optimized by using the following code
SELECT SINGLE * FROM T100 INTO T100_WA
WHERE SPRSL = 'D'
AND ARBGB = '00'
AND MSGNR = '999'.
Select Statements Aggregate Functions
If you want to find the maximum, minimum, sum and average value or the count of a database column, use a select list with aggregate functions instead of computing the aggregates yourself.
Some of the Aggregate functions allowed in SAP are MAX, MIN, AVG, SUM, COUNT, COUNT( * )
Consider the following extract.
Maxno = 0.
Select * from zflight where airln = LF and cntry = IN.
Check zflight-fligh > maxno.
Maxno = zflight-fligh.
Endselect.
The above mentioned code can be much more optimized by using the following code.
Select max( fligh ) from zflight into maxno where airln = LF and cntry = IN.
Select Statements For All Entries
The for all entries creates a where clause, where all the entries in the driver table are combined with OR. If the number of entries in the driver table is larger than rsdb/max_blocking_factor, several similar SQL statements are executed to limit the length of the WHERE clause.
The plus
Large amount of data
Mixing processing and reading of data
Fast internal reprocessing of data
Fast
The Minus
Difficult to program/understand
Memory could be critical (use FREE or PACKAGE size)
Points to be must considered FOR ALL ENTRIES
Check that data is present in the driver table
Sorting the driver table
Removing duplicates from the driver table
Consider the following piece of extract
Loop at int_cntry.
Select single * from zfligh into int_fligh
where cntry = int_cntry-cntry.
Append int_fligh.
Endloop.
The above mentioned can be more optimized by using the following code.
Sort int_cntry by cntry.
Delete adjacent duplicates from int_cntry.
If NOT int_cntry[] is INITIAL.
Select * from zfligh appending table int_fligh
For all entries in int_cntry
Where cntry = int_cntry-cntry.
Endif.
Select Statements Select Over more than one Internal table
1. Its better to use a views instead of nested Select statements.
SELECT * FROM DD01L INTO DD01L_WA
WHERE DOMNAME LIKE 'CHAR%'
AND AS4LOCAL = 'A'.
SELECT SINGLE * FROM DD01T INTO DD01T_WA
WHERE DOMNAME = DD01L_WA-DOMNAME
AND AS4LOCAL = 'A'
AND AS4VERS = DD01L_WA-AS4VERS
AND DDLANGUAGE = SY-LANGU.
ENDSELECT.
The above code can be more optimized by extracting all the data from view DD01V_WA
SELECT * FROM DD01V INTO DD01V_WA
WHERE DOMNAME LIKE 'CHAR%'
AND DDLANGUAGE = SY-LANGU.
ENDSELECT
2. To read data from several logically connected tables use a join instead of nested Select statements. Joins are preferred only if all the primary key are available in WHERE clause for the tables that are joined. If the primary keys are not provided in join the Joining of tables itself takes time.
SELECT * FROM EKKO INTO EKKO_WA.
SELECT * FROM EKAN INTO EKAN_WA
WHERE EBELN = EKKO_WA-EBELN.
ENDSELECT.
ENDSELECT.
The above code can be much more optimized by the code written below.
SELECT PF1 PF2 FF3 FF4 INTO TABLE ITAB
FROM EKKO AS P INNER JOIN EKAN AS F
ON PEBELN = FEBELN.
3. Instead of using nested Select loops it is often better to use subqueries.
SELECT * FROM SPFLI
INTO TABLE T_SPFLI
WHERE CITYFROM = 'FRANKFURT'
AND CITYTO = 'NEW YORK'.
SELECT * FROM SFLIGHT AS F
INTO SFLIGHT_WA
FOR ALL ENTRIES IN T_SPFLI
WHERE SEATSOCC < F~SEATSMAX
AND CARRID = T_SPFLI-CARRID
AND CONNID = T_SPFLI-CONNID
AND FLDATE BETWEEN '19990101' AND '19990331'.
ENDSELECT.
The above mentioned code can be even more optimized by using subqueries instead of for all entries.
SELECT * FROM SFLIGHT AS F INTO SFLIGHT_WA
WHERE SEATSOCC < F~SEATSMAX
AND EXISTS ( SELECT * FROM SPFLI
WHERE CARRID = F~CARRID
AND CONNID = F~CONNID
AND CITYFROM = 'FRANKFURT'
AND CITYTO = 'NEW YORK' )
AND FLDATE BETWEEN '19990101' AND '19990331'.
ENDSELECT.
1. Table operations should be done using explicit work areas rather than via header lines.
READ TABLE ITAB INTO WA WITH KEY K = 'X BINARY SEARCH.
IS MUCH FASTER THAN USING
READ TABLE ITAB INTO WA WITH KEY K = 'X'.
If TAB has n entries, linear search runs in O( n ) time, whereas binary search takes only O( log2( n ) ).
2. Always try to use binary search instead of linear search. But dont forget to sort your internal table before that.
READ TABLE ITAB INTO WA WITH KEY K = 'X'. IS FASTER THAN USING
READ TABLE ITAB INTO WA WITH KEY (NAME) = 'X'.
3. A dynamic key access is slower than a static one, since the key specification must be evaluated at runtime.
4. A binary search using secondary index takes considerably less time.
5. LOOP ... WHERE is faster than LOOP/CHECK because LOOP ... WHERE evaluates the specified condition internally.
LOOP AT ITAB INTO WA WHERE K = 'X'.
" ...
ENDLOOP.
The above code is much faster than using
LOOP AT ITAB INTO WA.
CHECK WA-K = 'X'.
" ...
ENDLOOP.
6. Modifying selected components using MODIFY itab TRANSPORTING f1 f2.. accelerates the task of updating a line of an internal table.
WA-DATE = SY-DATUM.
MODIFY ITAB FROM WA INDEX 1 TRANSPORTING DATE.
The above code is more optimized as compared to
WA-DATE = SY-DATUM.
MODIFY ITAB FROM WA INDEX 1.
7. Accessing the table entries directly in a "LOOP ... ASSIGNING ..." accelerates the task of updating a set of lines of an internal table considerably
Modifying selected components only makes the program faster as compared to Modifying all lines completely.
e.g,
LOOP AT ITAB ASSIGNING <WA>.
I = SY-TABIX MOD 2.
IF I = 0.
<WA>-FLAG = 'X'.
ENDIF.
ENDLOOP.
The above code works faster as compared to
LOOP AT ITAB INTO WA.
I = SY-TABIX MOD 2.
IF I = 0.
WA-FLAG = 'X'.
MODIFY ITAB FROM WA.
ENDIF.
ENDLOOP.
8. If collect semantics is required, it is always better to use to COLLECT rather than READ BINARY and then ADD.
LOOP AT ITAB1 INTO WA1.
READ TABLE ITAB2 INTO WA2 WITH KEY K = WA1-K BINARY SEARCH.
IF SY-SUBRC = 0.
ADD: WA1-VAL1 TO WA2-VAL1,
WA1-VAL2 TO WA2-VAL2.
MODIFY ITAB2 FROM WA2 INDEX SY-TABIX TRANSPORTING VAL1 VAL2.
ELSE.
INSERT WA1 INTO ITAB2 INDEX SY-TABIX.
ENDIF.
ENDLOOP.
The above code uses BINARY SEARCH for collect semantics. READ BINARY runs in O( log2(n) ) time. The above piece of code can be more optimized by
LOOP AT ITAB1 INTO WA.
COLLECT WA INTO ITAB2.
ENDLOOP.
SORT ITAB2 BY K.
COLLECT, however, uses a hash algorithm and is therefore independent
of the number of entries (i.e. O(1)) .
9. "APPEND LINES OF itab1 TO itab2" accelerates the task of appending a table to another table considerably as compared to LOOP-APPEND-ENDLOOP.
APPEND LINES OF ITAB1 TO ITAB2.
This is more optimized as compared to
LOOP AT ITAB1 INTO WA.
APPEND WA TO ITAB2.
ENDLOOP.
10. DELETE ADJACENT DUPLICATES accelerates the task of deleting duplicate entries considerably as compared to READ-LOOP-DELETE-ENDLOOP.
DELETE ADJACENT DUPLICATES FROM ITAB COMPARING K.
This is much more optimized as compared to
READ TABLE ITAB INDEX 1 INTO PREV_LINE.
LOOP AT ITAB FROM 2 INTO WA.
IF WA = PREV_LINE.
DELETE ITAB.
ELSE.
PREV_LINE = WA.
ENDIF.
ENDLOOP.
11. "DELETE itab FROM ... TO ..." accelerates the task of deleting a sequence of lines considerably as compared to DO -DELETE-ENDDO.
DELETE ITAB FROM 450 TO 550.
This is much more optimized as compared to
DO 101 TIMES.
DELETE ITAB INDEX 450.
ENDDO.
12. Copying internal tables by using ITAB2[ ] = ITAB1[ ] as compared to LOOP-APPEND-ENDLOOP.
ITAB2[] = ITAB1[].
This is much more optimized as compared to
REFRESH ITAB2.
LOOP AT ITAB1 INTO WA.
APPEND WA TO ITAB2.
ENDLOOP.
13. Specify the sort key as restrictively as possible to run the program faster.
SORT ITAB BY K. makes the program runs faster as compared to SORT ITAB.
Internal Tables contd
Hashed and Sorted tables
1. For single read access hashed tables are more optimized as compared to sorted tables.
2. For partial sequential access sorted tables are more optimized as compared to hashed tables
Hashed And Sorted Tables
Point # 1
Consider the following example where HTAB is a hashed table and STAB is a sorted table
DO 250 TIMES.
N = 4 * SY-INDEX.
READ TABLE HTAB INTO WA WITH TABLE KEY K = N.
IF SY-SUBRC = 0.
" ...
ENDIF.
ENDDO.
This runs faster for single read access as compared to the following same code for sorted table
DO 250 TIMES.
N = 4 * SY-INDEX.
READ TABLE STAB INTO WA WITH TABLE KEY K = N.
IF SY-SUBRC = 0.
" ...
ENDIF.
ENDDO.
Point # 2
Similarly for Partial Sequential access the STAB runs faster as compared to HTAB
LOOP AT STAB INTO WA WHERE K = SUBKEY.
" ...
ENDLOOP.
This runs faster as compared to
LOOP AT HTAB INTO WA WHERE K = SUBKEY.
" ...
ENDLOOP.
01-25-2008 3:02 PM
Please look at the sample code below. You can select from the table outside the loop using for all entries and then use read statements in the loop. Again the delete statement within the loop will cause performance issues. In your code your delete statament is not doing anything so I have excluded it. If the deletion of the entries in table tab1 is necessary for later processing, create a field of type CHAR1 in table tab1, mark the records to be deleted by modifying the record with 'X' in this field and after the loop delete all the entries with one delete statement where this field in 'X'.
types: begin of ty_tablename,
objnr type tablename-objnr,
end of ty_tablename.
data: tab2 like table of tab1,
t_tablename type hashed table of ty_tablename
with unique key objnr.
if not tab1[] is initial.
tab2[] = tab1[].
sort tab2 with field.
delete adjacent duplicates from tab2 comparing field.
select objnr
from tablename
into table of t_tablname
for all entries in tab2
where objnr eq tab2-field.
endif.
loop at tab1.
read table t_tablname with key objnr = tab1-field
transporting no fields.
if sy-subrc ne 0.
perform sleset.
endif.
endloop.
01-29-2008 6:14 AM
Hi!
Put the select statement before the loop for all entries in tab1.
Now inside the loop use Read statement for objnr = tab1-field.
01-29-2008 6:21 AM
HI
points to improve performance in the report
Ways of Performance Tuning
1. Selection Criteria
2. Select Statements
Select Queries
SQL Interface
Aggregate Functions
For all Entries
Select Over more than one internal table
Selection Criteria
1. Restrict the data to the selection criteria itself, rather than filtering it out using the ABAP code using CHECK statement.
2. Select with selection list.
SELECT * FROM SBOOK INTO SBOOK_WA.
CHECK: SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
ENDSELECT.
The above code can be much more optimized by the code written below which avoids CHECK, selects with selection list
SELECT CARRID CONNID FLDATE BOOKID FROM SBOOK INTO TABLE T_SBOOK
WHERE SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
Select Statements Select Queries
1. Avoid nested selects
SELECT * FROM EKKO INTO EKKO_WA.
SELECT * FROM EKAN INTO EKAN_WA
WHERE EBELN = EKKO_WA-EBELN.
ENDSELECT.
ENDSELECT.
The above code can be much more optimized by the code written below.
SELECT P~F1 P~F2 F~F3 F~F4 INTO TABLE ITAB
FROM EKKO AS P INNER JOIN EKAN AS F
ON P~EBELN = F~EBELN.
Note: A simple SELECT loop is a single database access whose result is passed to the ABAP program line by line. Nested SELECT loops mean that the number of accesses in the inner loop is multiplied by the number of accesses in the outer loop. One should therefore use nested SELECT loops only if the selection in the outer loop contains very few lines or the outer loop is a SELECT SINGLE statement.
2. Select all the records in a single shot using into table clause of select statement rather than to use Append statements.
SELECT * FROM SBOOK INTO SBOOK_WA.
CHECK: SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
ENDSELECT.
The above code can be much more optimized by the code written below which avoids CHECK, selects with selection list and puts the data in one shot using into table
SELECT CARRID CONNID FLDATE BOOKID FROM SBOOK INTO TABLE T_SBOOK
WHERE SBOOK_WA-CARRID = 'LH' AND
SBOOK_WA-CONNID = '0400'.
3. When a base table has multiple indices, the where clause should be in the order of the index, either a primary or a secondary index.
To choose an index, the optimizer checks the field names specified in the where clause and then uses an index that has the same order of the fields. In certain scenarios, it is advisable to check whether a new index can speed up the performance of a program. This will come handy in programs that access data from the finance tables.
4. For testing existence, use Select.. Up to 1 rows statement instead of a Select-Endselect-loop with an Exit.
SELECT * FROM SBOOK INTO SBOOK_WA
UP TO 1 ROWS
WHERE CARRID = 'LH'.
ENDSELECT.
The above code is more optimized as compared to the code mentioned below for testing existence of a record.
SELECT * FROM SBOOK INTO SBOOK_WA
WHERE CARRID = 'LH'.
EXIT.
ENDSELECT.
5. Use Select Single if all primary key fields are supplied in the Where condition .
If all primary key fields are supplied in the Where conditions you can even use Select Single.
Select Single requires one communication with the database system, whereas Select-Endselect needs two.
Select Statements SQL Interface
1. Use column updates instead of single-row updates
to update your database tables.
SELECT * FROM SFLIGHT INTO SFLIGHT_WA.
SFLIGHT_WA-SEATSOCC =
SFLIGHT_WA-SEATSOCC - 1.
UPDATE SFLIGHT FROM SFLIGHT_WA.
ENDSELECT.
The above mentioned code can be more optimized by using the following code
UPDATE SFLIGHT
SET SEATSOCC = SEATSOCC - 1.
2. For all frequently used Select statements, try to use an index.
SELECT * FROM SBOOK CLIENT SPECIFIED INTO SBOOK_WA
WHERE CARRID = 'LH'
AND CONNID = '0400'.
ENDSELECT.
The above mentioned code can be more optimized by using the following code
SELECT * FROM SBOOK CLIENT SPECIFIED INTO SBOOK_WA
WHERE MANDT IN ( SELECT MANDT FROM T000 )
AND CARRID = 'LH'
AND CONNID = '0400'.
ENDSELECT.
3. Using buffered tables improves the performance considerably.
Bypassing the buffer increases the network considerably
SELECT SINGLE * FROM T100 INTO T100_WA
BYPASSING BUFFER
WHERE SPRSL = 'D'
AND ARBGB = '00'
AND MSGNR = '999'.
The above mentioned code can be more optimized by using the following code
SELECT SINGLE * FROM T100 INTO T100_WA
WHERE SPRSL = 'D'
AND ARBGB = '00'
AND MSGNR = '999'.
Select Statements Aggregate Functions
If you want to find the maximum, minimum, sum and average value or the count of a database column, use a select list with aggregate functions instead of computing the aggregates yourself.
Some of the Aggregate functions allowed in SAP are MAX, MIN, AVG, SUM, COUNT, COUNT( * )
Consider the following extract.
Maxno = 0.
Select * from zflight where airln = LF and cntry = IN.
Check zflight-fligh > maxno.
Maxno = zflight-fligh.
Endselect.
The above mentioned code can be much more optimized by using the following code.
Select max( fligh ) from zflight into maxno where airln = LF and cntry = IN.
Select Statements For All Entries
The for all entries creates a where clause, where all the entries in the driver table are combined with OR. If the number of entries in the driver table is larger than rsdb/max_blocking_factor, several similar SQL statements are executed to limit the length of the WHERE clause.
The plus
Large amount of data
Mixing processing and reading of data
Fast internal reprocessing of data
Fast
The Minus
Difficult to program/understand
Memory could be critical (use FREE or PACKAGE size)
Points to be must considered FOR ALL ENTRIES
Check that data is present in the driver table
Sorting the driver table
Removing duplicates from the driver table
Consider the following piece of extract
Loop at int_cntry.
Select single * from zfligh into int_fligh
where cntry = int_cntry-cntry.
Append int_fligh.
Endloop.
The above mentioned can be more optimized by using the following code.
Sort int_cntry by cntry.
Delete adjacent duplicates from int_cntry.
If NOT int_cntry[] is INITIAL.
Select * from zfligh appending table int_fligh
For all entries in int_cntry
Where cntry = int_cntry-cntry.
Endif.
Select Statements Select Over more than one Internal table
1. Its better to use a views instead of nested Select statements.
SELECT * FROM DD01L INTO DD01L_WA
WHERE DOMNAME LIKE 'CHAR%'
AND AS4LOCAL = 'A'.
SELECT SINGLE * FROM DD01T INTO DD01T_WA
WHERE DOMNAME = DD01L_WA-DOMNAME
AND AS4LOCAL = 'A'
AND AS4VERS = DD01L_WA-AS4VERS
AND DDLANGUAGE = SY-LANGU.
ENDSELECT.
The above code can be more optimized by extracting all the data from view DD01V_WA
SELECT * FROM DD01V INTO DD01V_WA
WHERE DOMNAME LIKE 'CHAR%'
AND DDLANGUAGE = SY-LANGU.
ENDSELECT
2. To read data from several logically connected tables use a join instead of nested Select statements. Joins are preferred only if all the primary key are available in WHERE clause for the tables that are joined. If the primary keys are not provided in join the Joining of tables itself takes time.
SELECT * FROM EKKO INTO EKKO_WA.
SELECT * FROM EKAN INTO EKAN_WA
WHERE EBELN = EKKO_WA-EBELN.
ENDSELECT.
ENDSELECT.
The above code can be much more optimized by the code written below.
SELECT P~F1 P~F2 F~F3 F~F4 INTO TABLE ITAB
FROM EKKO AS P INNER JOIN EKAN AS F
ON P~EBELN = F~EBELN.
3. Instead of using nested Select loops it is often better to use subqueries.
SELECT * FROM SPFLI
INTO TABLE T_SPFLI
WHERE CITYFROM = 'FRANKFURT'
AND CITYTO = 'NEW YORK'.
SELECT * FROM SFLIGHT AS F
INTO SFLIGHT_WA
FOR ALL ENTRIES IN T_SPFLI
WHERE SEATSOCC < F~SEATSMAX
AND CARRID = T_SPFLI-CARRID
AND CONNID = T_SPFLI-CONNID
AND FLDATE BETWEEN '19990101' AND '19990331'.
ENDSELECT.
The above mentioned code can be even more optimized by using subqueries instead of for all entries.
SELECT * FROM SFLIGHT AS F INTO SFLIGHT_WA
WHERE SEATSOCC < F~SEATSMAX
AND EXISTS ( SELECT * FROM SPFLI
WHERE CARRID = F~CARRID
AND CONNID = F~CONNID
AND CITYFROM = 'FRANKFURT'
AND CITYTO = 'NEW YORK' )
AND FLDATE BETWEEN '19990101' AND '19990331'.
ENDSELECT.
1. Table operations should be done using explicit work areas rather than via header lines.
READ TABLE ITAB INTO WA WITH KEY K = 'X BINARY SEARCH.
IS MUCH FASTER THAN USING
READ TABLE ITAB INTO WA WITH KEY K = 'X'.
If TAB has n entries, linear search runs in O( n ) time, whereas binary search takes only O( log2( n ) ).
2. Always try to use binary search instead of linear search. But dont forget to sort your internal table before that.
READ TABLE ITAB INTO WA WITH KEY K = 'X'. IS FASTER THAN USING
READ TABLE ITAB INTO WA WITH KEY (NAME) = 'X'.
3. A dynamic key access is slower than a static one, since the key specification must be evaluated at runtime.
4. A binary search using secondary index takes considerably less time.
5. LOOP ... WHERE is faster than LOOP/CHECK because LOOP ... WHERE evaluates the specified condition internally.
LOOP AT ITAB INTO WA WHERE K = 'X'.
" ...
ENDLOOP.
The above code is much faster than using
LOOP AT ITAB INTO WA.
CHECK WA-K = 'X'.
" ...
ENDLOOP.
6. Modifying selected components using MODIFY itab TRANSPORTING f1 f2.. accelerates the task of updating a line of an internal table.
WA-DATE = SY-DATUM.
MODIFY ITAB FROM WA INDEX 1 TRANSPORTING DATE.
The above code is more optimized as compared to
WA-DATE = SY-DATUM.
MODIFY ITAB FROM WA INDEX 1.
7. Accessing the table entries directly in a "LOOP ... ASSIGNING ..." accelerates the task of updating a set of lines of an internal table considerably
Modifying selected components only makes the program faster as compared to Modifying all lines completely.
e.g,
LOOP AT ITAB ASSIGNING <WA>.
I = SY-TABIX MOD 2.
IF I = 0.
<WA>-FLAG = 'X'.
ENDIF.
ENDLOOP.
The above code works faster as compared to
LOOP AT ITAB INTO WA.
I = SY-TABIX MOD 2.
IF I = 0.
WA-FLAG = 'X'.
MODIFY ITAB FROM WA.
ENDIF.
ENDLOOP.
8. If collect semantics is required, it is always better to use to COLLECT rather than READ BINARY and then ADD.
LOOP AT ITAB1 INTO WA1.
READ TABLE ITAB2 INTO WA2 WITH KEY K = WA1-K BINARY SEARCH.
IF SY-SUBRC = 0.
ADD: WA1-VAL1 TO WA2-VAL1,
WA1-VAL2 TO WA2-VAL2.
MODIFY ITAB2 FROM WA2 INDEX SY-TABIX TRANSPORTING VAL1 VAL2.
ELSE.
INSERT WA1 INTO ITAB2 INDEX SY-TABIX.
ENDIF.
ENDLOOP.
The above code uses BINARY SEARCH for collect semantics. READ BINARY runs in O( log2(n) ) time. The above piece of code can be more optimized by
LOOP AT ITAB1 INTO WA.
COLLECT WA INTO ITAB2.
ENDLOOP.
SORT ITAB2 BY K.
COLLECT, however, uses a hash algorithm and is therefore independent
of the number of entries (i.e. O(1)) .
9. "APPEND LINES OF itab1 TO itab2" accelerates the task of appending a table to another table considerably as compared to LOOP-APPEND-ENDLOOP.
APPEND LINES OF ITAB1 TO ITAB2.
This is more optimized as compared to
LOOP AT ITAB1 INTO WA.
APPEND WA TO ITAB2.
ENDLOOP.
10. DELETE ADJACENT DUPLICATES accelerates the task of deleting duplicate entries considerably as compared to READ-LOOP-DELETE-ENDLOOP.
DELETE ADJACENT DUPLICATES FROM ITAB COMPARING K.
This is much more optimized as compared to
READ TABLE ITAB INDEX 1 INTO PREV_LINE.
LOOP AT ITAB FROM 2 INTO WA.
IF WA = PREV_LINE.
DELETE ITAB.
ELSE.
PREV_LINE = WA.
ENDIF.
ENDLOOP.
11. "DELETE itab FROM ... TO ..." accelerates the task of deleting a sequence of lines considerably as compared to DO -DELETE-ENDDO.
DELETE ITAB FROM 450 TO 550.
This is much more optimized as compared to
DO 101 TIMES.
DELETE ITAB INDEX 450.
ENDDO.
12. Copying internal tables by using ITAB2[ ] = ITAB1[ ] as compared to LOOP-APPEND-ENDLOOP.
ITAB2] = ITAB1[.
This is much more optimized as compared to
REFRESH ITAB2.
LOOP AT ITAB1 INTO WA.
APPEND WA TO ITAB2.
ENDLOOP.
13. Specify the sort key as restrictively as possible to run the program faster.
SORT ITAB BY K. makes the program runs faster as compared to SORT ITAB.
Internal Tables contd
Hashed and Sorted tables
1. For single read access hashed tables are more optimized as compared to sorted tables.
2. For partial sequential access sorted tables are more optimized as compared to hashed tables
Hashed And Sorted Tables
Point # 1
Consider the following example where HTAB is a hashed table and STAB is a sorted table
DO 250 TIMES.
N = 4 * SY-INDEX.
READ TABLE HTAB INTO WA WITH TABLE KEY K = N.
IF SY-SUBRC = 0.
" ...
ENDIF.
ENDDO.
This runs faster for single read access as compared to the following same code for sorted table
DO 250 TIMES.
N = 4 * SY-INDEX.
READ TABLE STAB INTO WA WITH TABLE KEY K = N.
IF SY-SUBRC = 0.
" ...
ENDIF.
ENDDO.
Point # 2
Similarly for Partial Sequential access the STAB runs faster as compared to HTAB
LOOP AT STAB INTO WA WHERE K = SUBKEY.
" ...
ENDLOOP.
This runs faster as compared to
LOOP AT HTAB INTO WA WHERE K = SUBKEY.
" ...
ENDLOOP.
Kindly Reward Points If Found Usefull,
Cheers,
Chaitanya.