Regarding COLLECT stmt usage in an ABAP Program.

Question

Hi All,
Could anyone please explain if the COLLECT statement really hampers the performance of the program, to a large extent.
If it is so, please explain how the performance can be improved with out using the same.
Thanks & Regards,
Goutham.

Answer 1

COLLECT allows you to create unique or summarized datasets. The system first tries to find a table entry corresponding to the table key. (See also Defining Keys for Internal Tables). The key values are taken either from the header line of the internal table itab, or from the explicitly-specified work area wa. The line type of itab must be flat - that is, it cannot itself contain any internal tables. All the components that do not belong to the key must be numeric types ( ABAP Numeric Types).
Notes
COLLECT allows you to create a unique or summarized dataset, and you should only use it when this is necessary. If neither of these characteristics are required, or where the nature of the table in the application means that it is impossible for duplicate entries to occur, you should use INSERT [wa INTO] TABLE itab instead of COLLECT. If you do need the table to be unique or summarized, COLLECT is the most efficient way to achieve it.
If you use COLLECT with a work area, the work area must be compatible with the line type of the internal table.
If you edit a standard table using COLLECT, you should only use the COLLECT or MODIFY ... TRANSPORTING f1 f2 ... statements (where none of f1, f2, ... may be in the key). Only then can you be sure that:
-The internal table actually is unique or summarized
-COLLECT runs efficiently. The check whether the dataset
already contains an entry with the same key has a constant
search time (hash procedure).
If you use any other table modification statements, the check for entries in the dataset with the same key can only run using a linear search (and will accordingly take longer). You can use the function module ABL_TABLE_HASH_STATE to test whether the COLLECT has a constant or linear search time for a given standard table.
Example
Summarized sales figures by company:
TYPES: BEGIN OF COMPANY,
        NAME(20) TYPE C,
        SALES    TYPE I,
      END OF COMPANY.
DATA: COMP    TYPE COMPANY,
      COMPTAB TYPE HASHED TABLE OF COMPANY
                                WITH UNIQUE KEY NAME.
COMP-NAME = 'Duck'.  COMP-SALES = 10. COLLECT COMP INTO COMPTAB.
COMP-NAME = 'Tiger'. COMP-SALES = 20. COLLECT COMP INTO COMPTAB.
COMP-NAME = 'Duck'.  COMP-SALES = 30. COLLECT COMP INTO COMPTAB.
Table COMPTAB now has the following contents:
          NAME    | SALES
          Duck    |   40
          Tiger   |   20