topic Re: Itab Performance! in Application Development and Automation Discussions

Itab Performance!

Former Member — Wed, 05 Sep 2007 12:14:58 GMT

Hi!

we ve different itabs

Standard

SOrted

Hashed

Which is best to use? gives good performance? good to use in program?

Thanks!

Rahul.

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:19:23 GMT

Hi,

Standard Internal Tables

Standard tables have a linear index. You can access them using either the index or the key. If you use the key, the response time is in linear relationship to the number of table entries. The key of a standard table is always non-unique, and you may not include any specification for the uniqueness in the table definition.

This table type is particularly appropriate if you want to address individual table entries using the index. This is the quickest way to access table entries. To fill a standard table, append lines using the (APPEND) statement. You should read, modify and delete lines by referring to the index (INDEX option with the relevant ABAP command). The response time for accessing a standard table is in linear relation to the number of table entries. If you need to use key access, standard tables are appropriate if you can fill and process the table in separate steps. For example, you can fill a standard table by appending records and then sort it. If you then use key access with the binary search option (BINARY), the response time is in logarithmic relation to

the number of table entries.

Sorted Internal Tables

Sorted tables are always saved correctly sorted by key. They also have a linear key, and, like standard tables, you can access them using either the table index or the key. When you use the key, the response time is in logarithmic relationship to the number of table entries, since the system uses a binary search. The key of a sorted table can be either unique, or non-unique, and you must specify either UNIQUE or NON-UNIQUE in the table definition. Standard tables and sorted tables both belong to the generic group index tables.

This table type is particularly suitable if you want the table to be sorted while you are still adding entries to it. You fill the table using the (INSERT) statement, according to the sort sequence defined in the table key. Table entries that do not fit are recognised before they are inserted. The response time for access using the key is in logarithmic relation to the number of

table entries, since the system automatically uses a binary search. Sorted tables are appropriate for partially sequential processing in a LOOP, as long as the WHERE condition contains the beginning of the table key.

Hashed Internal Tables

Hashes tables have no internal linear index. You can only access hashed tables by specifying the key. The response time is constant, regardless of the number of table entries, since the search uses a hash algorithm. The key of a hashed table must be unique, and you must specify UNIQUE in the table definition.

This table type is particularly suitable if you want mainly to use key access for table entries. You cannot access hashed tables using the index. When you use key access, the response time remains constant, regardless of the number of table entries. As with database tables, the key of a hashed table is always unique. Hashed tables are therefore a useful way of constructing and

using internal tables that are similar to database tables.

Regards

Sudheer

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:23:19 GMT

Hi,

Choosing a Table Type

The table type (and particularly the access method) that you will use depends on how the typical internal table operations will be most frequently executed.

Standard tables

standard tables are particularly useful if you can fill and process the table in separate steps. For example, you could fill the table by appending entries, and then sort it. If you use the binary search option with key access, the response time is logarithmically proportional to the number of table entries.

Sorted tables

This is the most appropriate type if you need a table which is sorted as you fill it. You fill sorted tables using the INSERT statement. Entries are inserted according to the sort sequence defined through the table key. Any illegal entries are recognized as soon as you try to add them to the table. The response time for key access is logarithmically proportional to the number of table entries, since the system always uses a binary search. Sorted tables are particularly useful for

partially sequential processing in a LOOP if you specify the beginning of the table key in the WHERE condition.

Hashed tables

This is the most appropriate type for any table where the main operation is key access. You cannot access a hashed table using its index. The response time for key access remains constant, regardless of the number of table entries. Like database tables, hashed tables always have a unique key. Hashed tables are useful if you want to construct and use an internal table which resembles a database table or for processing large amounts of data.

Regards,

Bhaskar

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:23:28 GMT

Hi!

Can u pls give some specific answer to my question

Which itab is best to use? why?

Thanks.

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:25:34 GMT

Hi Rahul,

Sorted is best but to avoid complexity we generally used Standard!

Sorted is faster though it recommanded to use Standard itabs!

Regards,

Mehfuze

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:26:59 GMT

Hi Rahul,

Use Standard!

Though it depends on sitution.

Regards

Mehfuze

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:28:30 GMT

hi,

you can check the performance of the below two program which ultimately shows their performances.

READ on a unique sorted table

Entries: 1000
Line width: 100, key width: 20
STAB is a unique sorted table, 250 entries are read

DO 250 TIMES.

N = 4 * SY-INDEX.

READ TABLE STAB INTO WA WITH TABLE KEY K = N.

IF SY-SUBRC = 0.

" ...

ENDIF.

ENDDO.

READ on a unique hashed table

Entries: 1000
Line width: 100, key width: 20
HTAB is a hased table, 250 entries are read

DO 250 TIMES.

N = 4 * SY-INDEX.

READ TABLE HTAB INTO WA WITH TABLE KEY K = N.

IF SY-SUBRC = 0.

" ...

ENDIF.

ENDDO.

Entries in a sorted table are located by binary search.

The costs depend on the number of entries in the table (O (log n)).

Entries in a hashed table are located by an internal hash-algorithm

The costs are constant (O (1)), i.e. they do not depend on the table

size.

Hashed tables are optimized for single entry access, whereas sorted

tables are optimized for partial sequential loop operations (see the

separate example).

reward point if find this useful

Regards

Siva

Refer se30

Message was edited by:

SivaKumar

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:39:50 GMT

Hi rahul,

Standard tables

This is the most appropriate type if you are going to address the individual table entries using the index. Index access is the quickest possible access. You should fill a standard table by appending lines (ABAP APPEND statement), and read, modify and delete entries by specifying the index (INDEX option with the relevant ABAP command). The access time for a standard table increases in a linear relationship with the number of table entries. If you need key access, standard tables are particularly useful if you can fill and process the table in separate steps. For example, you could fill the table by appending entries, and then sort it. If you use the binary search option with key access, the response time is logarithmically proportional to the number of table entries.

Sorted tables

Hashed tables

AND

Index Tables

Index table is only used to specify the type of generic parameters in a FORM or FUNCTION. That means that you can't create a table of type INDEX.

Internal tables are not DB tables. Standard and Sorted tables in combined are basically called as Index tables and there nothing else. Here is the hierarchy

ANY TABLE

| |

Index Tables Hashed Table

| |

Standard Table Sorted Table

Types of internal tablesSTANDARD table Key access to a standard table uses a linear search. This means that the time required for a search is in linear relation to the number of table entries. You should use index operations to access standard tables. 2 SORTED tableDefines the table as one that is always saved correctly sorted. Key access to a sorted table uses a binary key. If the key is not unique, the system takes the entry with the lowest index. The runtime required for key access is logarithmically related to the number of table entries. 3 HASHED tableDefines the table as one that is managed with an internal hash procedureYou can only access a hashed table using the generic key operations or other generic operations ( SORT, LOOP, and so on). Explicit or implicit index operations (such as LOOP ... FROM oe INSERT itab within a LOOP) are not allowed. 4 INDEX tableA table that can be accessed using an index.Index table is only used to specify the type of generic parameters in a FORM or FUNCTION. That means that you can't create a table of type INDEX.Standard tables and sorted tables are index tables.5 ANY tableAny table is only used to specify the type of generic parameters in a FORM or FUNCTION. That means that you can't create a table of type ANY.Standard, sorted and hashed tables belongs to ANY tables

Regards,

Kumar.

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 12:44:04 GMT

hi,

standard tables: used for normal purposes. i.e to store data

sorted tables : special requirement such as all data while entering only should be sorted like dat. here sorted table uses all key fields

hashed tables: for quick accessing of data from a internal table. used when performance is considered. hashed tables use a hash algorithms.

if helpful reward some points.

with regards,

Suresh Aluri.

Re: Itab Performance!

Former Member — Wed, 05 Sep 2007 13:10:51 GMT

Hi!

Thanks for your replies!

Any specific reason why we go for standard tables without going for others.

Thanks!