Modify key in Hashed table
Hi All,
I have hashehed internal table like this.
data : it_zawcumsetz like hashed table of zawcumsetz with unique key
KTONR_OPUS ZZ_AWC WAERS_OPUS.
I am geeting entries in table.
LOOP AT it_zawcumsetz into wa_zawcumsetz.
IF wa_zawcumsetz-zz_awc IS INITIAL.
wa_zawcumsetz-zz_awc = 'X'. "New value is * for
ENDIF.
MODIFY TABLE it_zawcumsetz FROM wa_zawcumsetz.
ENDLOOP.
i want to modify key value in loop.
Rather than append from wa to another internal table is not possiable.
Can anybody please tell me how to solve this pblm.
Thanks,
Hi Katta.
If you created a hashed table just to improve the MODIFY inside the loop, change your itab to a standard table and use field symbol:
DATA: it_zawcumsetz TYPE TABLE OF zawcumsetz.
FIELD-SYMBOLS: <fs_zawcumsetz> LIKE LINE OF it_zawcumsetz.
LOOP AT it_zawcumsetz ASSIGNING <fs_zawcumsetz>.
IF <fs_zawcumsetz>-zz_awc IS INITIAL.
<fs_zawcumsetz>-zz_awc = 'X'.
ENDIF.
ENDLOOP.
If you can't change to a standard table, maybe you can duplicate the itab, just for the loop:
DATA: it_std TYPE TABLE OF zawcumsetz.
FIELD-SYMBOLS: <fs_std> LIKE LINE OF it_std.
it_std = it_zawcumsetz.
LOOP AT it_std ASSIGNING <fs_std>.
IF <fs_std>-zz_awc IS INITIAL.
<fs_std>-zz_awc = 'X'.
ENDIF.
ENDLOOP.
it_zawcumsetz = it_std.
REFRESH it_std.
Regards
Darley
Similar Messages
-
Date Object as a key in Hash table
Hi,
I'm having a hash table with date object as key , the purpose is I can pick the value which is available in given date range. Consider the below example
Coffee Powder[Code CODE1] - Effective 21-Jan & Expiry 20-Jun
Coffee Powder[Code CODE1] - Effective 22-Jun & Expiry 30-Dec
Meat[Code CODE2] - Effective 21 - Jan & Expiry 1 - Feb
Meat[Code CODE2] - Effective 2 Feb & Expiry 6 - Feb
Currently I'm using the following hashtable & it has the structure Key - Code & Value [ List of objects] ]
CODE1- List[ Coffe Powder - 21 Jan - 20 Jun , Coffee Powder - 22 Jun - 30 Dec ]
CODE2- List[ Meat - 21 Jan - 01 Feb, Meat - 02 Feb - 06 Feb ]
To get the value which is valid for the given date , i need to get the list by passing the code & iterate the list to get the best matched value.
Example , if I want the Coffee Powder Information which is valid on 1 Feb. I need to get pass the code ( CODE 1 ) which will returns the list of objects. After we need to iterate the list to get the best match.
Instead of iteration , is there any way to maintain the hashtable & get the results quicker..?
Thx.To get a benefit out of the HashMaps quick access to keys you you'd need an exact match between your search date and a key date.
Can you cluster your Map-Content? eg.: do you always serch for a complete month?
Then you could change your Map from Map<Date,Object> to Map<Date,List<Object>> where Date is "normalised" to the first Day in month 00:00 o clock (UTC or local...).
You could also consider an additional map (Map<Date,List<Date>>) where you group the actual keys of the original Map by the expected search clusters.
bye
TPD -
Hi,
In my last thread i had asked about the ways of deleting the cube contents selectively using a job/FM and i was suggested this by one of you.
CALL FUNCTION 'RSDRD_SEL_DELETION'
EXPORTING
I_DATATARGET = 'YOUR_CUBE'
I_THX_SEL = L_THX_SEL
I_AUTHORITY_CHECK = 'X'
I_THRESHOLD = '1.0000E-01'
I_MODE = 'C'
I_NO_LOGGING = ''
I_PARALLEL_DEGREE = 1
I_NO_COMMIT = ''
CHANGING
C_T_MSG = L_T_MSG.
Although the FM is the correct one the structure L_THX_SEL is a hashed table structure and i am not aware how to fill values into it. My requirement is to give a condition for the 0CALDAY info-object i.e 0CALDAY < 30 days. Please suggest me.
Regadrs,
Pramod MHI,
Internal Tables
Internal tables provide a means of taking data from a fixed structure and storing it in working memory in ABAP. The data is stored line by line in memory, and each line has the same structure. In ABAP, internal tables fulfill the function of arrays. Since they are dynamic data objects, they save the programmer the task of dynamic memory management in his or her programs. You should use internal tables whenever you want to process a dataset with a fixed structure within a program. A particularly important use for internal tables is for storing and formatting data from a database table within a program. They are also a good way of including very complicated data structures in an ABAP program.
Data Type of an Internal Table
The data type of an internal table is fully specified by its line type, key, and table type.
Line Type
The line type of an internal table can be any data type. The data type of an internal table is normally a structure. Each component of the structure is a column in the internal table. However, the line type may also be elementary or another internal table.
Key
The key identifies table rows. There are two kinds of key for internal tables - the standard key and a user-defined key. You can specify whether the key should be UNIQUE or NON-UNIQUE. Internal tables with a unique key cannot contain duplicate entries. The uniqueness depends on the table access method.
At tables with structured row type, the standard key is formed from all character-type columns of the internal table. If a table has an elementary line type, the default key is the entire line. The default key of an internal table whose line type is an internal table, the default key is empty. At tables with non-structured row type, the standard key consists of the entire row. If the row type is also a table, an empty key is defined.
The user-defined key can contain any columns of the internal table that are no internal table themselves, and do not contain internal tables. References are allowed as table keys. Internal tables with a user-defined key are called key tables. When you define the key, the sequence of the key fields is significant. You should remember this, for example, if you intend to sort the table according to the key.
Table type
The table type determines how ABAP will access individual table entries. Internal tables can be divided into three types:
Standard tables have an internal linear index. From a particular size upwards, the indexes of internal tables are administered as trees. In this case, the index administration overhead increases in logarithmic and not linear relation to the number of lines. The system can access records either by using the table index or the key. The response time for key access is proportional to the number of entries in the table. The key of a standard table is always non-unique. You cannot specify a unique key. This means that standard tables can always be filled very quickly, since the system does not have to check whether there are already existing entries.
Sorted tables are always saved sorted by the key. They also have an internal index. The system can access records either by using the table index or the key. The response time for key access is logarithmically proportional 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. When you define the table, you must specify whether the key is to be UNIQUE or NON-UNIQUE. Standard tables and sorted tables are known generically as index tables.
Hashed tables have no linear index. You can only access a hashed table using its key. The response time is independent of the number of table entries, and is constant, since the system access the table entries using a hash algorithm. The key of a hashed table must be unique. When you define the table, you must specify the key as UNIQUE.
Generic Internal Tables
Unlike other local data types in programs, you do not have to specify the data type of an internal table fully. Instead, you can specify a generic construction, that is, the key or key and line type of an internal table data type may remain unspecified. You can use generic internal tables to specify the types of field symbols and the interface parameters of procedures . You cannot use them to declare data objects.
Internal Tables as Dynamic Data Objects
Internal tables are always completely specified regarding row type, key and access type. However, the number of lines is not fixed. Thus internal tables are dynamic data objects, since they can contain any number of lines of a particular type. The only restriction on the number of lines an internal table may contain are the limits of your system installation. The maximum memory that can be occupied by an internal table (including its internal administration) is 2 gigabytes. A more realistic figure is up to 500 megabytes. An additional restriction for hashed tables is that they may not contain more than 2 million entries. The line types of internal tables can be any ABAP data types - elementary, structured, or internal tables. The individual lines of an internal table are called table lines or table entries. Each component of a structured line is called a column in the internal table.
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
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 APPENDstatement), 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 (BINARY) 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 INSERTstatement. 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 WHEREcondition.
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.
If help full please give me max Reward -
Hi all
what exactly are the SORTED & HASHED tables??
Regards
SriniInternal tables are the core of ABAP. They are like soul of a body. For any program we use
internal tables extensively. We can use Internal tables like normal data base tables only, but the
basic difference is the memory allocated for internal tables is temporary. Once the program is
closed the memory allocated for internal tables will also be out of memory.
But while using the internal tables, there are many performance issues to be considered. i.e which
type of internal table to be used for the program..like standard internal table, hashed internal
table or sorted internal table etc..
Internal tables
Internal tables provide a means of taking data from a fixed structure and storing it in working memory in ABAP. The data is stored line by
line in memory, and each line has the same structure. In ABAP, internal tables fulfill the function of arrays. Since they are dynamic data
objects, they save the programmer the task of dynamic memory management in his or her programs. You should use internal tables
whenever you want to process a dataset with a fixed structure within a program. A particularly important use for internal tables is for
storing and formatting data from a database table within a program. They are also a good way of including very complicated data
structures in an ABAP program.
Like all elements in the ABAP type concept, internal tables can exist both as data types and as data objects A data type is the abstract
description of an internal table, either in a program or centrally in the ABAP Dictionary, that you use to create a concrete data object. The
data type is also an attribute of an existing data object.
Internal Tables as Data Types
Internal tables and structures are the two structured data types in ABAP. The data type of an internal table is fully specified by its line type,
key, and table type.
Line type
The line type of an internal table can be any data type. The data type of an internal table is normally a structure. Each component of the
structure is a column in the internal table. However, the line type may also be elementary or another internal table.
Key
The key identifies table rows. There are two kinds of key for internal tables - the standard key and a user-defined key. You can specify
whether the key should be UNIQUE or NON-UNIQUE. Internal tables with a unique key cannot contain duplicate entries. The uniqueness
depends on the table access method.
If a table has a structured line type, its default key consists of all of its non-numerical columns that are not references or themselves
internal tables. If a table has an elementary line type, the default key is the entire line. The default key of an internal table whose line type
is an internal table, the default key is empty.
The user-defined key can contain any columns of the internal table that are not references or themselves internal tables. Internal tables
with a user-defined key are called key tables. When you define the key, the sequence of the key fields is significant. You should remember
this, for example, if you intend to sort the table according to the key.
Table type
The table type determines how ABAP will access individual table entries. Internal tables can be divided into three types:
Standard tables have an internal linear index. From a particular size upwards, the indexes of internal tables are administered as trees. In
this case, the index administration overhead increases in logarithmic and not linear relation to the number of lines. The system can access
records either by using the table index or the key. The response time for key access is proportional to the number of entries in the table.
The key of a standard table is always non-unique. You cannot specify a unique key. This means that standard tables can always be filled
very quickly, since the system does not have to check whether there are already existing entries.
Sorted tables are always saved sorted by the key. They also have an internal index. The system can access records either by using the
table index or the key. The response time for key access is logarithmically proportional 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. When you define the table, you must specify whether
the key is to be unique or not. Standard tables and sorted tables are known generically as index tables.
Hashed tables have no linear index. You can only access a hashed table using its key. The response time is independent of the number of
table entries, and is constant, since the system access the table entries using a hash algorithm. The key of a hashed table must be unique.
When you define the table, you must specify the key as UNIQUE.
Generic Internal Tables
Unlike other local data types in programs, you do not have to specify the data type of an internal table fully. Instead, you can specify a
generic construction, that is, the key or key and line type of an internal table data type may remain unspecified. You can use generic
internal tables to specify the types of field symbols and the interface parameters of procedures . You cannot use them to declare data
objects.
Internal Tables as Dynamic Data Objects
Data objects that are defined either with the data type of an internal table, or directly as an internal table, are always fully defined in
respect of their line type, key and access method. However, the number of lines is not fixed. Thus internal tables are dynamic data objects,
since they can contain any number of lines of a particular type. The only restriction on the number of lines an internal table may contain are
the limits of your system installation. The maximum memory that can be occupied by an internal table (including its internal administration)
is 2 gigabytes. A more realistic figure is up to 500 megabytes. An additional restriction for hashed tables is that they may not contain more
than 2 million entries. The line types of internal tables can be any ABAP data types - elementary, structured, or internal tables. The
individual lines of an internal table are called table lines or table entries. Each component of a structured line is called a column in the
internal table.
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
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
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.
Creating Internal Tables
Like other elements in the ABAP type concept, you can declare internal tables as abstract data
types in programs or in the ABAP Dictionary, and then use them to define data objects.
Alternatively, you can define them directly as data objects. When you create an internal table as a
data object, you should ensure that only the administration entry which belongs to an internal
table is declared statically. The minimum size of an internal table is 256 bytes. This is important if an
internal table occurs as a component of an aggregated data object, since even empty internal
tables within tables can lead to high memory usage. (In the next functional release, the size of the
table header for an initial table will be reduced to 8 bytes). Unlike all other ABAP data objects, you
do not have to specify the memory required for an internal table. Table rows are added to and
deleted from the table dynamically at runtime by the various statements for adding and deleting
records.
You can create internal tables in different types.
You can create standard internal table and then make it sort in side the program.
The same way you can change to hashed internal tables also.
There will be some performance issues with regard to standard internal tables/ hashed internal
tables/ sorted internal tables.
Internal table types
This section describes how to define internal tables locally in a program. You can also define internal tables globally as data types in the
ABAP Dictionary.
Like all local data types in programs , you define internal tables using the TYPES statement. If you do not refer to an existing table type
using the TYPE or LIKE addition, you can use the TYPES statement to construct a new local internal table in your program.
TYPES <t> TYPE|LIKE <tabkind> OF <linetype> [WITH <key>]
[INITIAL SIZE <n>].
After TYPE or LIKE, there is no reference to an existing data type. Instead, the type constructor occurs:
<tabkind> OF <linetype> [WITH <key>]
The type constructor defines the table type <tabkind>, the line type <linetype>, and the key <key> of the internal table <t>.
You can, if you wish, allocate an initial amount of memory to the internal table using the INITIAL SIZE addition.
Table type
You can specify the table type <tabkind> as follows:
Generic table types
INDEX TABLE
For creating a generic table type with index access.
ANY TABLE
For creating a fully-generic table type.
Data types defined using generic types can currently only be used for field symbols and for interface parameters in procedures . The generic
type INDEX TABLE includes standard tables and sorted tables. These are the two table types for which index access is allowed. You cannot
pass hashed tables to field symbols or interface parameters defined in this way. The generic type ANY TABLE can represent any table. You
can pass tables of all three types to field symbols and interface parameters defined in this way. However, these field symbols and
parameters will then only allow operations that are possible for all tables, that is, index operations are not allowed.
Fully-Specified Table Types
STANDARD TABLE or TABLE
For creating standard tables.
<b>SORTED TABLE</b>
For creating sorted tables.
<b>HASHED TABLE</b>
For creating hashed tables.
Fully-specified table types determine how the system will access the entries in the table in key operations. It uses a linear search for
standard tables, a binary search for sorted tables, and a search using a hash algorithm for hashed tables.
Line type
For the line type <linetype>, you can specify:
Any data type if you are using the TYPE addition. This can be a predefined ABAP type, a local type in the program, or a data type from the
ABAP Dictionary. If you specify any of the generic elementary types C, N, P, or X, any attributes that you fail to specify (field length, number
of decimal places) are automatically filled with the default values. You cannot specify any other generic types.
Any data object recognized within the program at that point if you are using the LIKE addition. The line type adopts the fully-specified data
type of the data object to which you refer. Except for within classes, you can still use the LIKE addition to refer to database tables and
structures in the ABAP Dictionary (for compatibility reasons).
All of the lines in the internal table have the fully-specified technical attributes of the specified data type.
Key
You can specify the key <key> of an internal table as follows:
[UNIQUE|NON-UNIQUE] KEY <col1> ... <col n>
In tables with a structured line type, all of the components <coli> belong to the key as long as they are not internal tables or references,
and do not contain internal tables or references. Key fields can be nested structures. The substructures are expanded component by
component when you access the table using the key. The system follows the sequence of the key fields.
[UNIQUE|NON-UNIQUE] KEY TABLE LINE
If a table has an elementary line type (C, D, F, I, N, P, T, X), you can define the entire line as the key. If you try this for a table whose line
type is itself a table, a syntax error occurs. If a table has a structured line type, it is possible to specify the entire line as the key. However,
you should remember that this is often not suitable.
[UNIQUE|NON-UNIQUE] DEFAULT KEY
This declares the fields of the default key as the key fields. If the table has a structured line type, the default key contains all non-numeric
columns of the internal table that are not and do not contain references or internal tables. If the table has an elementary line type, the
default key is the entire line. The default key of an internal table whose line type is an internal table, the default key is empty.
Specifying a key is optional. If you do not specify a key, the system defines a table type with an arbitrary key. You can only use this to
define the types of field symbols and the interface parameters of procedures . For exceptions, refer to Special Features of Standard Tables.
The optional additions UNIQUE or NON-UNIQUE determine whether the key is to be unique or non-unique, that is, whether the table can
accept duplicate entries. If you do not specify UNIQUE or NON-UNIQUE for the key, the table type is generic in this respect. As such, it can
only be used for specifying types. When you specify the table type simultaneously, you must note the following restrictions:
You cannot use the UNIQUE addition for standard tables. The system always generates the NON-UNIQUE addition automatically.
You must always specify the UNIQUE option when you create a hashed table.
Initial Memory Requirement
You can specify the initial amount of main memory assigned to an internal table object when you define the data type using the following
addition:
INITIAL SIZE <n>
This size does not belong to the data type of the internal table, and does not affect the type check. You can use the above addition to
reserve memory space for <n> table lines when you declare the table object.
When this initial area is full, the system makes twice as much extra space available up to a limit of 8KB. Further memory areas of 12KB each
are then allocated.
You can usually leave it to the system to work out the initial memory requirement. The first time you fill the table, little memory is used. The
space occupied, depending on the line width, is 16 <= <n> <= 100.
It only makes sense to specify a concrete value of <n> if you can specify a precise number of table entries when you create the table and
need to allocate exactly that amount of memory (exception: Appending table lines to ranked lists). This can be particularly important for
deep-structured internal tables where the inner table only has a few entries (less than 5, for example).
To avoid excessive requests for memory, large values of <n> are treated as follows: The largest possible value of <n> is 8KB divided by the
length of the line. If you specify a larger value of <n>, the system calculates a new value so that n times the line width is around 12KB.
Examples
TYPES: BEGIN OF LINE,
COLUMN1 TYPE I,
COLUMN2 TYPE I,
COLUMN3 TYPE I,
END OF LINE.
TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.
The program defines a table type ITAB. It is a sorted table, with line type of the structure LINE and a unique key of the component
COLUMN1.
TYPES VECTOR TYPE HASHED TABLE OF I WITH UNIQUE KEY TABLE LINE.
TYPES: BEGIN OF LINE,
COLUMN1 TYPE I,
COLUMN2 TYPE I,
COLUMN3 TYPE I,
END OF LINE.
TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.
TYPES: BEGIN OF DEEPLINE,
FIELD TYPE C,
TABLE1 TYPE VECTOR,
TABLE2 TYPE ITAB,
END OF DEEPLINE.
TYPES DEEPTABLE TYPE STANDARD TABLE OF DEEPLINE
WITH DEFAULT KEY.
The program defines a table type VECTOR with type hashed table, the elementary line type I and a unique key of the entire table line. The
second table type is the same as in the previous example. The structure DEEPLINE contains the internal table as a component. The table
type DEEPTABLE has the line type DEEPLINE. Therefore, the elements of this internal table are themselves internal tables. The key is the
default key - in this case the column FIELD. The key is non-unique, since the table is a standard table.
Internal table objects
Internal tables are dynamic variable data objects. Like all variables, you declare them using the DATA statement. You can also declare static
internal tables in procedures using the STATICS statement, and static internal tables in classes using the CLASS-DATA statement. This
description is restricted to the DATA statement. However, it applies equally to the STATICS and CLASS-DATA statements.
Reference to Declared Internal Table Types
Like all other data objects, you can declare internal table objects using the LIKE or TYPE addition of the DATA statement.
DATA <itab> TYPE <type>|LIKE <obj> [WITH HEADER LINE].
Here, the LIKE addition refers to an existing table object in the same program. The TYPE addition can refer to an internal type in the
program declared using the TYPES statement, or a table type in the ABAP Dictionary.
You must ensure that you only refer to tables that are fully typed. Referring to generic table types (ANY TABLE, INDEX TABLE) or not
specifying the key fully is not allowed (for exceptions, refer to Special Features of Standard Tables).
The optional addition WITH HEADER line declares an extra data object with the same name and line type as the internal table. This data
object is known as the header line of the internal table. You use it as a work area when working with the internal table (see Using the
Header Line as a Work Area). When you use internal tables with header lines, you must remember that the header line and the body of the
table have the same name. If you have an internal table with header line and you want to address the body of the table, you must indicate
this by placing brackets after the table name (<itab>[]). Otherwise, ABAP interprets the name as the name of the header line and not of the
body of the table. You can avoid this potential confusion by using internal tables without header lines. In particular, internal tables nested
in structures or other internal tables must not have a header line, since this can lead to ambiguous expressions.
TYPES VECTOR TYPE SORTED TABLE OF I WITH UNIQUE KEY TABLE LINE.
DATA: ITAB TYPE VECTOR,
JTAB LIKE ITAB WITH HEADER LINE.
MOVE ITAB TO JTAB. <- Syntax error!
MOVE ITAB TO JTAB[].
The table object ITAB is created with reference to the table type VECTOR. The table object JTAB has the same data type as ITAB. JTAB also
has a header line. In the first MOVE statement, JTAB addresses the header line. Since this has the data type I, and the table type of ITAB
cannot be converted into an elementary type, the MOVE statement causes a syntax error. The second MOVE statement is correct, since
both operands are table objects.
Declaring New Internal Tables
You can use the DATA statement to construct new internal tables as well as using the LIKE or TYPE addition to refer to existing types or
objects. The table type that you construct does not exist in its own right; instead, it is only an attribute of the table object. You can refer to
it using the LIKE addition, but not using TYPE. The syntax for constructing a table object in the DATA statement is similar to that for defining
a table type in the TYPES statement.
DATA <itab> TYPE|LIKE <tabkind> OF <linetype> WITH <key>
[INITIAL SIZE <n>]
[WITH HEADER LINE].
As when you define a table type , the type constructor
<tabkind> OF <linetype> WITH <key>
defines the table type <tabkind>, the line type <linekind>, and the key <key> of the internal table <itab>. Since the technical attributes of
data objects are always fully specified, the table must be fully specified in the DATA statement. You cannot create generic table types (ANY
TABLE, INDEX TABLE), only fully-typed tables (STANDARD TABLE, SORTED TABLE, HASHED TABLE). You must also specify the key and whether
it is to be unique (for exceptions, refer to Special Features of Standard Tables).
As in the TYPES statement, you can, if you wish, allocate an initial amount of memory to the internal table using the INITIAL SIZE addition.
You can create an internal table with a header line using the WITH HEADER LINE addition. The header line is created under the same
conditions as apply when you refer to an existing table type.
DATA ITAB TYPE HASHED TABLE OF SPFLI
WITH UNIQUE KEY CARRID CONNID.
The table object ITAB has the type hashed table, a line type corresponding to the flat structure SPFLI from the ABAP Dictionary, and a
unique key with the key fields CARRID and CONNID. The internal table ITAB can be regarded as an internal template for the database table
SPFLI. It is therefore particularly suitable for working with data from this database table as long as you only access it using the key. -
What is the difference between standard,sorted and hash table
<b>can anyone say what is the difference between standard,sorted and hash tabl</b>
Hi,
Standard 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 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 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,
Ferry Lianto -
hello every one,
This is rahul
when we are declaring internal table by default it takes as standard table
but y don't we take hashed table they can get performance very well
hashed can perform very well than standard nahI
READ THIS POINTS
Internal tables are the core of ABAP. They are like soul of a body. For any program we use
internal tables extensively. We can use Internal tables like normal data base tables only, but the
basic difference is the memory allocated for internal tables is temporary. Once the program is
closed the memory allocated for internal tables will also be out of memory.
But while using the internal tables, there are many performance issues to be considered. i.e which
type of internal table to be used for the program..like standard internal table, hashed internal
table or sorted internal table etc..
Internal tables
Internal tables provide a means of taking data from a fixed structure and storing it in working memory in ABAP. The data is stored line by
line in memory, and each line has the same structure. In ABAP, internal tables fulfill the function of arrays. Since they are dynamic data
objects, they save the programmer the task of dynamic memory management in his or her programs. You should use internal tables
whenever you want to process a dataset with a fixed structure within a program. A particularly important use for internal tables is for
storing and formatting data from a database table within a program. They are also a good way of including very complicated data
structures in an ABAP program.
Like all elements in the ABAP type concept, internal tables can exist both as data types and as data objects A data type is the abstract
description of an internal table, either in a program or centrally in the ABAP Dictionary, that you use to create a concrete data object. The
data type is also an attribute of an existing data object.
Internal Tables as Data Types
Internal tables and structures are the two structured data types in ABAP. The data type of an internal table is fully specified by its line type,
key, and table type.
Line type
The line type of an internal table can be any data type. The data type of an internal table is normally a structure. Each component of the
structure is a column in the internal table. However, the line type may also be elementary or another internal table.
Key
The key identifies table rows. There are two kinds of key for internal tables - the standard key and a user-defined key. You can specify
whether the key should be UNIQUE or NON-UNIQUE. Internal tables with a unique key cannot contain duplicate entries. The uniqueness
depends on the table access method.
If a table has a structured line type, its default key consists of all of its non-numerical columns that are not references or themselves
internal tables. If a table has an elementary line type, the default key is the entire line. The default key of an internal table whose line type
is an internal table, the default key is empty.
The user-defined key can contain any columns of the internal table that are not references or themselves internal tables. Internal tables
with a user-defined key are called key tables. When you define the key, the sequence of the key fields is significant. You should remember
this, for example, if you intend to sort the table according to the key.
Table type
The table type determines how ABAP will access individual table entries. Internal tables can be divided into three types:
Standard tables have an internal linear index. From a particular size upwards, the indexes of internal tables are administered as trees. In
this case, the index administration overhead increases in logarithmic and not linear relation to the number of lines. The system can access
records either by using the table index or the key. The response time for key access is proportional to the number of entries in the table.
The key of a standard table is always non-unique. You cannot specify a unique key. This means that standard tables can always be filled
very quickly, since the system does not have to check whether there are already existing entries.
Sorted tables are always saved sorted by the key. They also have an internal index. The system can access records either by using the
table index or the key. The response time for key access is logarithmically proportional 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. When you define the table, you must specify whether
the key is to be unique or not. Standard tables and sorted tables are known generically as index tables.
Hashed tables have no linear index. You can only access a hashed table using its key. The response time is independent of the number of
table entries, and is constant, since the system access the table entries using a hash algorithm. The key of a hashed table must be unique.
When you define the table, you must specify the key as UNIQUE.
Generic Internal Tables
Unlike other local data types in programs, you do not have to specify the data type of an internal table fully. Instead, you can specify a
generic construction, that is, the key or key and line type of an internal table data type may remain unspecified. You can use generic
internal tables to specify the types of field symbols and the interface parameters of procedures . You cannot use them to declare data
objects.
Internal Tables as Dynamic Data Objects
Data objects that are defined either with the data type of an internal table, or directly as an internal table, are always fully defined in
respect of their line type, key and access method. However, the number of lines is not fixed. Thus internal tables are dynamic data objects,
since they can contain any number of lines of a particular type. The only restriction on the number of lines an internal table may contain are
the limits of your system installation. The maximum memory that can be occupied by an internal table (including its internal administration)
is 2 gigabytes. A more realistic figure is up to 500 megabytes. An additional restriction for hashed tables is that they may not contain more
than 2 million entries. The line types of internal tables can be any ABAP data types - elementary, structured, or internal tables. The
individual lines of an internal table are called table lines or table entries. Each component of a structured line is called a column in the
internal table.
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
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
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.
Creating Internal Tables
Like other elements in the ABAP type concept, you can declare internal tables as abstract data
types in programs or in the ABAP Dictionary, and then use them to define data objects.
Alternatively, you can define them directly as data objects. When you create an internal table as a
data object, you should ensure that only the administration entry which belongs to an internal
table is declared statically. The minimum size of an internal table is 256 bytes. This is important if an
internal table occurs as a component of an aggregated data object, since even empty internal
tables within tables can lead to high memory usage. (In the next functional release, the size of the
table header for an initial table will be reduced to 8 bytes). Unlike all other ABAP data objects, you
do not have to specify the memory required for an internal table. Table rows are added to and
deleted from the table dynamically at runtime by the various statements for adding and deleting
records.
You can create internal tables in different types.
You can create standard internal table and then make it sort in side the program.
The same way you can change to hashed internal tables also.
There will be some performance issues with regard to standard internal tables/ hashed internal
tables/ sorted internal tables.
Internal table types
This section describes how to define internal tables locally in a program. You can also define internal tables globally as data types in the
ABAP Dictionary.
Like all local data types in programs , you define internal tables using the TYPES statement. If you do not refer to an existing table type
using the TYPE or LIKE addition, you can use the TYPES statement to construct a new local internal table in your program.
TYPES <t> TYPE|LIKE <tabkind> OF <linetype> [WITH <key>]
[INITIAL SIZE <n>].
After TYPE or LIKE, there is no reference to an existing data type. Instead, the type constructor occurs:
<tabkind> OF <linetype> [WITH <key>]
The type constructor defines the table type <tabkind>, the line type <linetype>, and the key <key> of the internal table <t>.
You can, if you wish, allocate an initial amount of memory to the internal table using the INITIAL SIZE addition.
Table type
You can specify the table type <tabkind> as follows:
Generic table types
INDEX TABLE
For creating a generic table type with index access.
ANY TABLE
For creating a fully-generic table type.
Data types defined using generic types can currently only be used for field symbols and for interface parameters in procedures . The generic
type INDEX TABLE includes standard tables and sorted tables. These are the two table types for which index access is allowed. You cannot
pass hashed tables to field symbols or interface parameters defined in this way. The generic type ANY TABLE can represent any table. You
can pass tables of all three types to field symbols and interface parameters defined in this way. However, these field symbols and
parameters will then only allow operations that are possible for all tables, that is, index operations are not allowed.
Fully-Specified Table Types
STANDARD TABLE or TABLE
For creating standard tables.
SORTED TABLE
For creating sorted tables.
HASHED TABLE
For creating hashed tables.
Fully-specified table types determine how the system will access the entries in the table in key operations. It uses a linear search for
standard tables, a binary search for sorted tables, and a search using a hash algorithm for hashed tables.
Line type
For the line type <linetype>, you can specify:
Any data type if you are using the TYPE addition. This can be a predefined ABAP type, a local type in the program, or a data type from the
ABAP Dictionary. If you specify any of the generic elementary types C, N, P, or X, any attributes that you fail to specify (field length, number
of decimal places) are automatically filled with the default values. You cannot specify any other generic types.
Any data object recognized within the program at that point if you are using the LIKE addition. The line type adopts the fully-specified data
type of the data object to which you refer. Except for within classes, you can still use the LIKE addition to refer to database tables and
structures in the ABAP Dictionary (for compatibility reasons).
All of the lines in the internal table have the fully-specified technical attributes of the specified data type.
Key
You can specify the key <key> of an internal table as follows:
[UNIQUE|NON-UNIQUE] KEY <col1> ... <col n>
In tables with a structured line type, all of the components <coli> belong to the key as long as they are not internal tables or references,
and do not contain internal tables or references. Key fields can be nested structures. The substructures are expanded component by
component when you access the table using the key. The system follows the sequence of the key fields.
[UNIQUE|NON-UNIQUE] KEY TABLE LINE
If a table has an elementary line type (C, D, F, I, N, P, T, X), you can define the entire line as the key. If you try this for a table whose line
type is itself a table, a syntax error occurs. If a table has a structured line type, it is possible to specify the entire line as the key. However,
you should remember that this is often not suitable.
[UNIQUE|NON-UNIQUE] DEFAULT KEY
This declares the fields of the default key as the key fields. If the table has a structured line type, the default key contains all non-numeric
columns of the internal table that are not and do not contain references or internal tables. If the table has an elementary line type, the
default key is the entire line. The default key of an internal table whose line type is an internal table, the default key is empty.
Specifying a key is optional. If you do not specify a key, the system defines a table type with an arbitrary key. You can only use this to
define the types of field symbols and the interface parameters of procedures . For exceptions, refer to Special Features of Standard Tables.
The optional additions UNIQUE or NON-UNIQUE determine whether the key is to be unique or non-unique, that is, whether the table can
accept duplicate entries. If you do not specify UNIQUE or NON-UNIQUE for the key, the table type is generic in this respect. As such, it can
only be used for specifying types. When you specify the table type simultaneously, you must note the following restrictions:
You cannot use the UNIQUE addition for standard tables. The system always generates the NON-UNIQUE addition automatically.
You must always specify the UNIQUE option when you create a hashed table.
Initial Memory Requirement
You can specify the initial amount of main memory assigned to an internal table object when you define the data type using the following
addition:
INITIAL SIZE <n>
This size does not belong to the data type of the internal table, and does not affect the type check. You can use the above addition to
reserve memory space for <n> table lines when you declare the table object.
When this initial area is full, the system makes twice as much extra space available up to a limit of 8KB. Further memory areas of 12KB each
are then allocated.
You can usually leave it to the system to work out the initial memory requirement. The first time you fill the table, little memory is used. The
space occupied, depending on the line width, is 16 <= <n> <= 100.
It only makes sense to specify a concrete value of <n> if you can specify a precise number of table entries when you create the table and
need to allocate exactly that amount of memory (exception: Appending table lines to ranked lists). This can be particularly important for
deep-structured internal tables where the inner table only has a few entries (less than 5, for example).
To avoid excessive requests for memory, large values of <n> are treated as follows: The largest possible value of <n> is 8KB divided by the
length of the line. If you specify a larger value of <n>, the system calculates a new value so that n times the line width is around 12KB.
Examples
TYPES: BEGIN OF LINE,
COLUMN1 TYPE I,
COLUMN2 TYPE I,
COLUMN3 TYPE I,
END OF LINE.
TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.
The program defines a table type ITAB. It is a sorted table, with line type of the structure LINE and a unique key of the component
COLUMN1.
TYPES VECTOR TYPE HASHED TABLE OF I WITH UNIQUE KEY TABLE LINE.
TYPES: BEGIN OF LINE,
COLUMN1 TYPE I,
COLUMN2 TYPE I,
COLUMN3 TYPE I,
END OF LINE.
TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.
TYPES: BEGIN OF DEEPLINE,
FIELD TYPE C,
TABLE1 TYPE VECTOR,
TABLE2 TYPE ITAB,
END OF DEEPLINE.
TYPES DEEPTABLE TYPE STANDARD TABLE OF DEEPLINE
WITH DEFAULT KEY.
The program defines a table type VECTOR with type hashed table, the elementary line type I and a unique key of the entire table line. The
second table type is the same as in the previous example. The structure DEEPLINE contains the internal table as a component. The table
type DEEPTABLE has the line type DEEPLINE. Therefore, the elements of this internal table are themselves internal tables. The key is the
default key - in this case the column FIELD. The key is non-unique, since the table is a standard table.
Internal table objects
Internal tables are dynamic variable data objects. Like all variables, you declare them using the DATA statement. You can also declare static
internal tables in procedures using the STATICS statement, and static internal tables in classes using the CLASS-DATA statement. This
description is restricted to the DATA statement. However, it applies equally to the STATICS and CLASS-DATA statements.
Reference to Declared Internal Table Types
Like all other data objects, you can declare internal table objects using the LIKE or TYPE addition of the DATA statement.
DATA <itab> TYPE <type>|LIKE <obj> [WITH HEADER LINE].
Here, the LIKE addition refers to an existing table object in the same program. The TYPE addition can refer to an internal type in the
program declared using the TYPES statement, or a table type in the ABAP Dictionary.
You must ensure that you only refer to tables that are fully typed. Referring to generic table types (ANY TABLE, INDEX TABLE) or not
specifying the key fully is not allowed (for exceptions, refer to Special Features of Standard Tables).
The optional addition WITH HEADER line declares an extra data object with the same name and line type as the internal table. This data
object is known as the header line of the internal table. You use it as a work area when working with the internal table (see Using the
Header Line as a Work Area). When you use internal tables with header lines, you must remember that the header line and the body of the
table have the same name. If you have an internal table with header line and you want to address the body of the table, you must indicate
this by placing brackets after the table name (<itab>[]). Otherwise, ABAP interprets the name as the name of the header line and not of the
body of the table. You can avoid this potential confusion by using internal tables without header lines. In particular, internal tables nested
in structures or other internal tables must not have a header line, since this can lead to ambiguous expressions.
TYPES VECTOR TYPE SORTED TABLE OF I WITH UNIQUE KEY TABLE LINE.
DATA: ITAB TYPE VECTOR,
JTAB LIKE ITAB WITH HEADER LINE.
MOVE ITAB TO JTAB. <- Syntax error!
MOVE ITAB TO JTAB[].
The table object ITAB is created with reference to the table type VECTOR. The table object JTAB has the same data type as ITAB. JTAB also
has a header line. In the first MOVE statement, JTAB addresses the header line. Since this has the data type I, and the table type of ITAB
cannot be converted into an elementary type, the MOVE statement causes a syntax error. The second MOVE statement is correct, since
both operands are table objects.
Declaring New Internal Tables
You can use the DATA statement to construct new internal tables as well as using the LIKE or TYPE addition to refer to existing types or
objects. The table type that you construct does not exist in its own right; instead, it is only an attribute of the table object. You can refer to
it using the LIKE addition, but not using TYPE. The syntax for constructing a table object in the DATA statement is similar to that for defining
a table type in the TYPES statement.
DATA <itab> TYPE|LIKE <tabkind> OF <linetype> WITH <key>
[INITIAL SIZE <n>]
[WITH HEADER LINE].
As when you define a table type , the type constructor
<tabkind> OF <linetype> WITH <key>
defines the table type <tabkind>, the line type <linekind>, and the key <key> of the internal table <itab>. Since the technical attributes of
data objects are always fully specified, the table must be fully specified in the DATA statement. You cannot create generic table types (ANY
TABLE, INDEX TABLE), only fully-typed tables (STANDARD TABLE, SORTED TABLE, HASHED TABLE). You must also specify the key and whether
it is to be unique (for exceptions, refer to Special Features of Standard Tables).
As in the TYPES statement, you can, if you wish, allocate an initial amount of memory to the internal table using the INITIAL SIZE addition.
You can create an internal table with a header line using the WITH HEADER LINE addition. The header line is created under the same
conditions as apply when you refer to an existing table type.
DATA ITAB TYPE HASHED TABLE OF SPFLI
WITH UNIQUE KEY CARRID CONNID.
The table object ITAB has the type hashed table, a line type corresponding to the flat structure SPFLI from the ABAP Dictionary, and a
unique key with the key fields CARRID and CONNID. The internal table ITAB can be regarded as an internal template for the database table
SPFLI. It is therefore particularly suitable for working with data from this database table as long as you only access it using the key. -
How Hash tables can be used in PI mapping
Hi Experts,
I'm don't have any idea how we store the values in hash tables and how to implement them in mapping.
In my scenario I have two fields matnum and quantity.if matnum is not null ,then we have to check whether the matnum exists in hash table and also check whether the hash table is empty or not.
How we can do this in graphical message mapping?
how to store the variable matnum in a table?
If global variables are used, how to implement in mapping.how we call the keys from hash table ?Divya,
We have a similiar requirement for getting different values. Below param1 may you be matnum,param2 is quantity
What you need to do is first declare global varaible(A), fill hash table as below(B) and retrieve(C) based on index. You can tweak code based on your requirement
(A) Declare global variable(last icon in message mapping tool bar)
String globlalString[] = new String[10];
(B) Fill Hash Table
import java.util.Hashtable;
public void saveparam1(String[] param1,String[] param2,ResultList result,Container container){
Hashtable htparam1 = new Hashtable();
int Indx = 0;
for (int i = 0 ;i < param1.length ; i++) {
String strparam1 = param1<i>.trim();
if (strparam1.length() > 0) {
Object obj = htparam1.get(strparam1);
if (obj == null){
globlalString[Indx++] = strparam1 ;
htparam1.put(strparam1,strparam1);
if (Indx < globalString.length) {
for (int i = 0; i < param2.length ; i++) {
String strparam2 = param2<i>.trim();
if (strparam2.length() > 0) {
Object obj = htparam1.get(strparam2);
if (obj == null){
globalString[Indx++] = strparam2 ;
htparam1.put(strparam2,strparam2);
result.addValue(globalString[0]); // for first value
(C) for subsequent reading/accessing
//pass constant whatever number is required to this function
String retValue = "";
int indx = Integer.parseInt(index);
indx = indx - 1;
if ((indx >= 0) && (indx < globalString.length)){
retValue = globalString[indx];
return retValue;
Hope this helps! -
Hi..
I want to know that how we can define a hash table in ABAB.
And what are the advantages of that table?
Thanksonce you have data in your internal table, there is not much of a performance issue...unless of course it contains a huge number of entries...
i m not aware of such a possibility that an internal table can behave as both sorted and hashed...
if you go for a hashed table, the response time for your search will always be constant, regardless of the number of table entries....this is because the search uses a hash algorithm...u must specify the UNIQUE key for hashed tables.
just go thru this link for some more information...
http://www.sap-img.com/abap/what-are-different-types-of-internal-tables-and-their-usage.htm
read this...
Standard tables are managed system-internally by a logical index. New rows are either attached to the table or added at certain positions. The table key or the index identify individual rows.
Sorted tables are managed by a logical index (like standard tables). The entries are listed in ascending order according to table key.
Hashed tables are managed by a hash algorithm. There is no logical index. The entries are not ordered in the memory. The position of a row is calculated by specifying a key using a hash function.
Sorted tables store records in a "sorted" fashion at all times. It is faster to search through a sorted table vs a standard table. But performance is dictated by the amount of records in the internal table.
A hashed table's performance in reads is NOT dependent on the number of records. However, it is intended for reads that will return only and only one record. It uses a "side-table" with a hash algorithm to store off the physical location of the record in the actual internal table. It is not NECESSARILY sorted/organized in an meaningful order (like a sorted table is). Please note that changes to a hashed tables records must be managed carefully. Review SAP's on-help in SE38/80 about managing hashed tables.
TYPES: BEGIN OF TY_ITAB,
FIELD1 TYPE I,
FIELD2 TYPE I,
END OF TY_ITAB.
TYPES ITAB TYPE SORTED TABLE OF TY_ITAB WITH UNIQUE KEY FIELD1.....
FOR PROPER SYNTEX F1 HELP.... -
Hi all,
Can anyone explain me what is HASH table?
Thanks in Advance.......An internal table of type HASHED can be used to improve performance. Hashed tables have no linear index. You can only access hashed tables by specifying
the key. The system has its own hash algorithm for managing the table.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.A restriction for hashed tables is that they may not contain more than 2 million entries.
You can also chk the links
http://help.sap.com/saphelp_nw04/helpdata/en/fc/eb2fcc358411d1829f0000e829fbfe/content.htm
http://help.sap.com/saphelp_47x200/helpdata/en/90/8d7328b1af11d194f600a0c929b3c3/frameset.htm
If you have an internal table in your program which is used solely for lookup, it is good programming practice to use a hash table. The example below shows this, in combination with a method for buffering SELECT SINGLE results.
Code
*& Form select_dispo
Get MRP controller and in-house production time from material
and plant
--> MATNR Material
--> RESWK Plant
<-- DISPO MRP controller
<-- DZEIT In-house production time
form select_from_marc using matnr werks dispo dzeit.
types: begin of mrp_lookup_type,
matnr like marc-matnr,
werks like marc-werks,
dispo like marc-dispo,
dzeit like marc-dzeit,
end of mrp_lookup_type.
Define static hashed table to hold results
statics: st_mrp type hashed table of mrp_lookup_type
with unique key matnr werks.
data: l_wa_mrp type mrp_lookup_type.
clear dzeit.
See if data is in the table
read table st_mrp into l_wa_mrp with table key matnr = matnr
werks = werks.
If not in table, get it from the database
if not sy-subrc is initial.
select single dispo dzeit from marc
into corresponding fields of l_wa_mrp-dispo
where matnr eq matnr
and werks eq werks.
Insert into table
l_wa_mrp-matnr = matnr.
l_wa_mrp-werks = werks.
insert l_wa_mrp into table st_mrp.
endif.
dispo = l_wa_mrp-dispo. " MRP Controller
dzeit = l_wa_mrp-dzeit. " Inhouse production time
endform. " select_from_marc
reward points if helpful -
Hi Guys,
I have an internal table with employee name and its attributes, like address, family etc. Each employee can have multiple records in the table.
I want to create a table of tables with key as employee ID and rest of the employee attributes inside the table.
So each employee then will have one row in the main table and all its attributes will be in the inner table.
Can someone please share a sample code to achieve this?
Regards,
~MarkHi,
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.
Example:
TYPES VECTOR TYPE HASHED TABLE OF I WITH UNIQUE KEY TABLE
LINE.
TYPES: BEGIN OF LINE,
COLUMN1 TYPE I,
COLUMN2 TYPE I,
COLUMN3 TYPE I,
END OF LINE.
TYPES ITAB TYPE SORTED TABLE OF LINE WITH UNIQUE KEY COLUMN1.
TYPES: BEGIN OF DEEPLINE,
FIELD TYPE C,
TABLE1 TYPE VECTOR,
TABLE2 TYPE ITAB,
END OF DEEPLINE.
TYPES DEEPTABLE TYPE STANDARD TABLE OF DEEPLINE
WITH DEFAULT KEY.
The program defines a table type VECTOR with type hashed table, the elementary line type I and a unique key of the entire table line. The second table type is the same as in the previous example. The structure DEEPLINE contains the internal table as a component. The table type DEEPTABLE has the line type DEEPLINE. Therefore, the elements of this internal table are themselves internal tables. The key is the default key - in this case the column FIELD. The key is non-unique, since the table is a standard table.
Regards,
Bhaskar -
How about use partial key to loop at a hashed table?
Such as I want to loop a Internal table of BSID according to BKPF.
data itab_bsid type hashed table of BSID with unique key bukrs belnr gjahr buzid.
Loop at itab_bsid where bukrs = wa_bkpf-bukrs
and belnr = wa_bkpf-belnr
and gjahr = wa_bkpf-gjahr.
endloop.
I know if you use all key to access this hashed table ,it is certainly quick, and my question is when i use partial key of this internal hashed table to loop it, how about its performance.
Another question is in this case(BSID have many many record) , Sorted table and Hashed table , Which is better in performance.You can't cast b/w data reference which l_tax is and object reference which l_o_tax_code is.
osref is a generic object type and you store a reference to some object in it, right? So the question is: what kind of object you store there? Please note - this must be an object reference , not data reference .
i.e
"here goes some class
class zcl_spfli definition.
endclass.
class zcl_spfli implementation.
endclass.
"here is an OBJECT REFERENCE for it, (so I refer to a class) i.e persistent object to table SPFLI
data oref_spfli type ref to zcl_spfli.
"but here I have a DATA REFERENCE (so I refer to some data object) i.e DDIC structure SPFLI
data dref_spfli type ref to spfli.
So my OSREF can hold only oref_spfli but it not intended for dref_spfli . That's why you get this syntax error. Once you have stored reference to zcl_spfli in osref then you will be able to dereference it and access this object's attributes.
data: osref type osref.
create object osref_spfli.
osref = osref_spfli.
"now osref holds reference to object, you can deference it
oref_spfli ?= osref.
osref_spfli->some_attribute = ....
OSREFTAB is just a table whose line is of type OSREF (so can hold multiple object references - one in each line).
Regards
Marcin -
How to Implement a Chained Hash Table with Linked Lists
I'm making a migration from C/C++ to Java, and my task is to implement a Chained Hash Table with a Linked List. My problem is to put the strings(in this case names) hashed by the table using de Division Metod (H(k)= k mod N) in to a Linked list that is handling the colisions. My table has an interface implemented(public boolean insert(), public boolean findItem(), public void remove()). Any Help is needed. Thanks for everyone in advance.
OK. you have your hash table. What you want it to do is keep key/value pairs in linked lists, so that when there is a collision, you add the key/value pair to the linked list rather than searching for free space on the table.
This means that whenever you add an item, you hash it out, check to see if there is already a linked list and if not, create one and put it in that slot. Then in either case you add the key/value pair to the linked list if the key is not already on the linked list. If it is there you have to decide whether your requirements are to give an error or allow duplicate keys or just keep or modify one or the other (old/new).
When you are searching for a key, you hash it out once again and check to see if there is a linked list at that slot. If there is one, look for the key and if it's there, return it and if not, or if there was no linked list at that slot, return an error.
You aren't clear on whether you can simply use the provided linked-list implementations in the Java Collections or whether you have to cobble the linked list yourself. In any case, it's up to you.
Is this what you're asking?
Doug -
How to create hashed table in runtime
hi experts
how to create hashed table in runtime, please give me the coading style.
please help me.
regards
subhasisHi,
Have alook at the code, and pls reward points.
Use Hashed Tables to Improve Performance :
report zuseofhashedtables.
Program: ZUseOfHashedTables **
Author: XXXXXXXXXXXXXXXXXX **
Versions: 4.6b - 4.6c **
Notes: **
this program shows how we can use hashed tables to improve **
the responce time. **
It shows, **
1. how to declare hashed tables **
2. a cache-like technique to improve access to master data **
3. how to collect data using hashed tables **
4. how to avoid deletions of unwanted data **
Results: the test we run read about 31000 rows from mkpf, 150000 **
rows from mseg, 500 rows from makt and 400 from lfa1. **
it filled ht_lst with 24500 rows and displayed them in **
alv grid format. **
It needed about 65 seconds to perform this task (with **
all the db buffers empty) **
The same program with standard tables needed 140 seconds **
to run with the same recordset and with buffers filled in **
Objetive: show a list that consists of all the material movements **
'101' - '901' for a certain range of dates in mkpf-budat. **
the columns to be displayed are: **
mkpf-budat, **
mkpf-mblnr, **
mseg-lifnr, **
lfa1-name1, **
mkpf-xblnr, **
mseg-zeile **
mseg-charg, **
mseg-matnr, **
makt-maktx, **
mseg-erfmg, **
mseg-erfme. **
or show a sumary list by matnr - menge **
You'll have to create a pf-status called vista - **
See form set_pf_status for details **
tables used -
tables: mkpf,
mseg,
lfa1,
makt.
global hashed tables used
data: begin of wa_mkpf, "header
mblnr like mkpf-mblnr,
mjahr like mkpf-mjahr,
budat like mkpf-budat,
xblnr like mkpf-xblnr,
end of wa_mkpf.
data: ht_mkpf like hashed table of wa_mkpf
with unique key mblnr mjahr
with header line.
data: begin of wa_mseg, " line items
mblnr like mseg-mblnr,
mjahr like mseg-mjahr,
zeile like mseg-zeile,
bwart like mseg-bwart,
charg like mseg-charg,
matnr like mseg-matnr,
lifnr like mseg-lifnr,
erfmg like mseg-erfmg,
erfme like mseg-erfme,
end of wa_mseg.
data ht_mseg like hashed table of wa_mseg
with unique key mblnr mjahr zeile
with header line.
cache structure for lfa1 records
data: begin of wa_lfa1,
lifnr like lfa1-lifnr,
name1 like lfa1-name1,
end of wa_lfa1.
data ht_lfa1 like hashed table of wa_lfa1
with unique key lifnr
with header line.
cache structure for material related data
data: begin of wa_material,
matnr like makt-matnr,
maktx like makt-maktx,
end of wa_material.
data: ht_material like hashed table of wa_material
with unique key matnr
with header line.
result table
data: begin of wa_lst, "
budat like mkpf-budat,
mblnr like mseg-mblnr,
lifnr like mseg-lifnr,
name1 like lfa1-name1,
xblnr like mkpf-xblnr,
zeile like mseg-zeile,
charg like mseg-charg,
matnr like mseg-matnr,
maktx like makt-maktx,
erfmg like mseg-erfmg,
erfme like mseg-erfme,
mjahr like mseg-mjahr,
end of wa_lst.
data: ht_lst like hashed table of wa_lst
with unique key mblnr mjahr zeile
with header line.
data: begin of wa_lst1, " sumary by material
matnr like mseg-matnr,
maktx like makt-maktx,
erfmg like mseg-erfmg,
erfme like mseg-erfme,
end of wa_lst1.
data: ht_lst1 like hashed table of wa_lst1
with unique key matnr
with header line.
structures for alv grid display.
itabs
type-pools: slis.
data: it_lst like standard table of wa_lst with header line,
it_fieldcat_lst type slis_t_fieldcat_alv with header line,
it_sort_lst type slis_t_sortinfo_alv,
it_lst1 like standard table of wa_lst1 with header line,
it_fieldcat_lst1 type slis_t_fieldcat_alv with header line,
it_sort_lst1 type slis_t_sortinfo_alv.
structures
data: wa_sort type slis_sortinfo_alv,
ls_layout type slis_layout_alv.
global varialbes
data: g_lines type i.
data: g_repid like sy-repid,
ok_code like sy-ucomm.
selection-screen
"text: Dates:
select-options: so_budat for mkpf-budat default sy-datum.
"text: Material numbers.
select-options: so_matnr for mseg-matnr.
selection-screen uline.
selection-screen skip 1.
"Text: show summary by material.
parameters: gp_bymat as checkbox default ''.
start-of-selection.
perform get_data.
perform show_data.
end-of-selection.
FORM get_data *
form get_data.
select mblnr mjahr budat xblnr
into table ht_mkpf
from mkpf
where budat in so_budat. " make use of std index.
have we retrieved data from mkpf?
describe table ht_mkpf lines g_lines.
if g_lines > 0.
if true then retrieve all related records from mseg.
Doing this way we make sure that the access is by primary key
of mseg.
The reason is that is faster to filter them in memory
than to allow the db server to do it.
select mblnr mjahr zeile bwart charg
matnr lifnr erfmg erfme
into table ht_mseg
from mseg
for all entries in ht_mkpf
where mblnr = ht_mkpf-mblnr
and mjahr = ht_mkpf-mjahr.
endif.
fill t_lst or t_lst1 according to user's choice.
if gp_bymat = ' '.
perform fill_ht_lst.
else.
perform fill_ht_lst1.
endif.
endform.
form fill_ht_lst.
refresh ht_lst.
Example: how to discard unwanted data in an efficient way.
loop at ht_mseg.
filter unwanted data
check ht_mseg-bwart = '101' or ht_mseg-bwart = '901'.
check ht_mseg-matnr in so_matnr.
read header line.
read table ht_mkpf with table key mblnr = ht_mseg-mblnr
mjahr = ht_mseg-mjahr.
clear ht_lst.
* note : this may be faster if you specify field by field.
move-corresponding ht_mkpf to ht_lst.
move-corresponding ht_mseg to ht_lst.
perform read_lfa1 using ht_mseg-lifnr changing ht_lst-name1.
perform read_material using ht_mseg-matnr changing ht_lst-maktx.
insert table ht_lst.
endloop.
endform.
form fill_ht_lst1.
refresh ht_lst1.
Example: how to discard unwanted data in an efficient way.
hot to simulate a collect in a faster way
loop at ht_mseg.
filter unwanted data
check ht_mseg-bwart = '101' or ht_mseg-bwart = '901'.
check ht_mseg-matnr in so_matnr.
* note : this may be faster if you specify field by field.
read table ht_lst1 with table key matnr = ht_mseg-matnr
transporting erfmg.
if sy-subrc <> 0. " if matnr doesn't exist in sumary table
" insert a new record
ht_lst1-matnr = ht_mseg-matnr.
perform read_material using ht_mseg-matnr changing ht_lst1-maktx.
ht_lst1-erfmg = ht_mseg-erfmg.
ht_lst1-erfme = ht_mseg-erfme.
insert table ht_lst1.
else." a record was found.
" collect erfmg. To do so, fill in the unique key and add
" the numeric fields.
ht_lst1-matnr = ht_mseg-matnr.
add ht_mseg-erfmg to ht_lst1-erfmg.
modify table ht_lst1 transporting erfmg.
endif.
endloop.
endform.
implementation of cache for lfa1.
form read_lfa1 using p_lifnr changing p_name1.
read table ht_lfa1 with table key lifnr = p_lifnr
transporting name1.
if sy-subrc <> 0.
clear ht_lfa1.
ht_lfa1-lifnr = p_lifnr.
select single name1
into ht_lfa1-name1
from lfa1
where lifnr = p_lifnr.
if sy-subrc <> 0. ht_lfa1-name1 = 'n/a in lfa1'. endif.
insert table ht_lfa1.
endif.
p_name1 = ht_lfa1-name1.
endform.
implementation of cache for material data
form read_material using p_matnr changing p_maktx.
read table ht_material with table key matnr = p_matnr
transporting maktx.
if sy-subrc <> 0.
ht_material-matnr = p_matnr.
select single maktx into ht_material-maktx
from makt
where spras = sy-langu
and matnr = p_matnr.
if sy-subrc <> 0. ht_material-maktx = 'n/a in makt'. endif.
insert table ht_material.
endif.
p_maktx = ht_material-maktx.
endform.
form show_data.
if gp_bymat = ' '.
perform show_ht_lst.
else.
perform show_ht_lst1.
endif.
endform.
form show_ht_lst.
"needed because the FM can't use a hashed table.
it_lst[] = ht_lst[].
perform fill_layout using 'full display'
changing ls_layout.
perform fill_columns_lst.
perform sort_lst.
g_repid = sy-repid.
call function 'REUSE_ALV_GRID_DISPLAY'
exporting
i_callback_program = g_repid
i_callback_pf_status_set = 'SET_PF_STATUS'
is_layout = ls_layout
it_fieldcat = it_fieldcat_lst[]
it_sort = it_sort_lst
tables
t_outtab = it_lst
exceptions
program_error = 1
others = 2.
endform.
form show_ht_lst1.
"needed because the FM can't use a hashed table.
it_lst1[] = ht_lst1[].
perform fill_layout using 'Sumary by matnr'
changing ls_layout.
perform fill_columns_lst1.
perform sort_lst.
g_repid = sy-repid.
call function 'REUSE_ALV_GRID_DISPLAY'
exporting
i_callback_program = g_repid
i_callback_pf_status_set = 'SET_PF_STATUS'
is_layout = ls_layout
it_fieldcat = it_fieldcat_lst1[]
it_sort = it_sort_lst
tables
t_outtab = it_lst1
exceptions
program_error = 1
others = 2.
endform.
form fill_layout using p_window_titlebar
changing cs_layo type slis_layout_alv.
clear cs_layo.
cs_layo-window_titlebar = p_window_titlebar.
cs_layo-edit = 'X'.
cs_layo-edit_mode = space.
endform. " armar_layout_stock
form set_pf_status using rt_extab type slis_t_extab.
create a new status
and then select extras -> adjust template -> listviewer
set pf-status 'VISTA'.
endform. "set_pf_status
define add_lst.
clear it_fieldcat_lst.
it_fieldcat_lst-fieldname = &1.
it_fieldcat_lst-outputlen = &2.
it_fieldcat_lst-ddictxt = 'L'.
it_fieldcat_lst-seltext_l = &1.
it_fieldcat_lst-seltext_m = &1.
it_fieldcat_lst-seltext_m = &1.
if &1 = 'MATNR'.
it_fieldcat_lst-emphasize = 'C111'.
endif.
append it_fieldcat_lst.
end-of-definition.
define add_lst1.
clear it_fieldcat_lst.
it_fieldcat_lst1-fieldname = &1.
it_fieldcat_lst1-outputlen = &2.
it_fieldcat_lst1-ddictxt = 'L'.
it_fieldcat_lst1-seltext_l = &1.
it_fieldcat_lst1-seltext_m = &1.
it_fieldcat_lst1-seltext_m = &1.
append it_fieldcat_lst1.
end-of-definition.
form fill_columns_lst.
set columns for output.
refresh it_fieldcat_lst.
add_lst 'BUDAT' 10.
add_lst 'MBLNR' 10.
add_lst 'LIFNR' 10.
add_lst 'NAME1' 35.
add_lst 'XBLNR' 15.
add_lst 'ZEILE' 5.
add_lst 'CHARG' 10.
add_lst 'MATNR' 18.
add_lst 'MAKTX' 30.
add_lst 'ERFMG' 17.
add_lst 'ERFME' 5.
add_lst 'MJAHR' 4.
endform.
form fill_columns_lst1.
set columns for output.
refresh it_fieldcat_lst1.
add_lst1 'MATNR' 18.
add_lst1 'MAKTX' 30.
add_lst1 'ERFMG' 17.
add_lst1 'ERFME' 5..
endform.
Regards,
Ameet -
How can I use Hash Table when processing the data from cdpos and cdhdr
Hello Guru,
I've a question,
I need to reduce the access time to both cdhdr and cdpos.
Because may be I'll get a huge number of entries.
It looks like that by processing cdhdr and cdpos data will take many secondes,
it depends on how many data you need to find.
Hints : Putting instructions inside a form will slow down the program?
Also, I just want use Hash table and I need to put a loop-instruction going on the hash-table in form.
I know that it's no possible but I can declare an index inside my customized hash table.
For example :
DO
READ TABLE FOR specific_hash_table WITH KEY TABLE oindex = d_oindex.
Process data
d_oindex += 1.
UNTIL d_oindex = c_max_lines + 1.
Doing this would actually not necessary improve the performance.
Because It looks like I'm having a standard table, may be there's a hash function, but it could be a bad function.
Also I need to use for example COUNT (*) to know how many lines I get with the select.
FORM find_cdpos_data_with_loop
TABLES
i_otf_objcs TYPE STANDARD TABLE
USING
i_cdhdr_data TYPE HASHED TABLE
i_objcl TYPE j_objnr
* i_obj_lst TYPE any
i_option TYPE c
CHANGING
i_global TYPE STANDARD TABLE.
" Hint: cdpos is a cluster-table
CONSTANTS : objectid TYPE string VALUE 'objectid = i_obj_lst-objectid',
changenr TYPE string VALUE 'changenr = i_obj_lst-changenr',
tabname TYPE string VALUE 'tabname = i_otf_objcs-tablename',
tabnameo1 TYPE string VALUE 'tabname NE ''''',
tabnameo2 TYPE string VALUE 'tabname NE ''DRAD''',
fname TYPE string VALUE 'fname = i_otf_objcs-fieldname'.
DATA : BEGIN OF i_object_list OCCURS 0,
objectclas LIKE cdpos-objectclas,
objectid LIKE cdpos-objectid,
changenr LIKE cdpos-changenr,
END OF i_object_list.
DATA : i_cdpos LIKE TABLE OF i_object_list WITH HEADER LINE,
i_obj_lst LIKE LINE OF i_cdpos.
DATA : tabnamev2 TYPE string.
IF i_option EQ 'X'.
MOVE tabnameo2 TO tabnamev2.
ELSE.
MOVE tabnameo1 TO tabnamev2.
ENDIF.
*LOOP AT i_cdhdr_data TO i_obj_lst.
SELECT objectclas objectid changenr
INTO TABLE i_cdpos
FROM cdpos
FOR ALL ENTRIES IN i_otf_objcs
WHERE objectclas = i_objcl AND
(objectid) AND
(changenr) AND
(tabname) AND
(tabnamev2) AND
(fname).
LOOP AT i_cdpos.
APPEND i_cdpos-objectid TO i_global.
ENDLOOP.
*ENDLOOP.
ENDFORM. "find_cdpos_dataHey Mart,
This is what I met, unfortunately I get the same performance with for all entries.
But with a lot of more code.
FORM find_cdpos_data
TABLES
i_otf_objcs TYPE STANDARD TABLE
USING
i_objcl TYPE j_objnr
i_obj_lst TYPE any
i_option TYPE c
CHANGING
i_global TYPE STANDARD TABLE.
" Hint: cdpos is a cluster-table
CONSTANTS : objectid TYPE string VALUE 'objectid = i_obj_lst-objectid',
changenr TYPE string VALUE 'changenr = i_obj_lst-changenr',
tabname TYPE string VALUE 'tabname = i_otf_objcs-tablename',
tabnameo1 TYPE string VALUE 'tabname NE ''''',
tabnameo2 TYPE string VALUE 'tabname NE ''DRAD''',
fname TYPE string VALUE 'fname = i_otf_objcs-fieldname'.
* DATA : BEGIN OF i_object_list OCCURS 0,
* objectclas LIKE cdpos-objectclas,
* objectid LIKE cdpos-objectid,
* changenr LIKE cdpos-changenr,
* END OF i_object_list.
** complete modified code [begin]
DATA : BEGIN OF i_object_list OCCURS 0,
objectclas LIKE cdpos-objectclas,
objectid LIKE cdpos-objectid,
changenr LIKE cdpos-changenr,
tabname LIKE cdpos-tabname,
fname LIKE cdpos-fname,
END OF i_object_list.
** complete modified code [end]
DATA : i_cdpos LIKE TABLE OF i_object_list WITH HEADER LINE.
DATA : tabnamev2 TYPE string.
** complete modified code [begin]
FIELD-SYMBOLS : <otf> TYPE ANY,
<otf_field_tabname>,
<otf_field_fname>.
** complete modified code [end]
IF i_option EQ 'X'.
MOVE tabnameo2 TO tabnamev2.
ELSE.
MOVE tabnameo1 TO tabnamev2.
ENDIF.
** SELECT objectclas objectid changenr
** INTO TABLE i_cdpos
* SELECT objectid
* APPENDING CORRESPONDING FIELDS OF TABLE i_global
* FROM cdpos
* FOR ALL ENTRIES IN i_otf_objcs
* WHERE objectclas = i_objcl AND
* (objectid) AND
* (changenr) AND
* (tabname) AND
* (tabnamev2) AND
* (fname).
** complete modified code [begin]
SELECT objectid tabname fname
INTO CORRESPONDING FIELDS OF TABLE i_cdpos
FROM cdpos
WHERE objectclas = i_objcl AND
(objectid) AND
(changenr) AND
(tabnamev2).
ASSIGN LOCAL COPY OF i_otf_objcs TO <otf>.
LOOP AT i_cdpos.
LOOP AT i_otf_objcs INTO <otf>.
ASSIGN COMPONENT 'TABLENAME' OF STRUCTURE <otf> TO <otf_field_tabname>.
ASSIGN COMPONENT 'FIELDNAME' OF STRUCTURE <otf> TO <otf_field_fname>.
IF ( <otf_field_tabname> EQ i_cdpos-tabname ) AND ( <otf_field_fname> EQ i_cdpos-fname ).
APPEND i_cdpos-objectid TO i_global.
RETURN.
ENDIF.
ENDLOOP.
ENDLOOP.
** complete modified code [end]
** LOOP AT i_cdpos.
** APPEND i_cdpos-objectid TO i_global.
** ENDLOOP.
ENDFORM. "find_cdpos_data -
I would like to know if there is a method of class Hashtable to update values in a Hash Table. I know about methods "put", "get", "remove" and "contains", but what I need is to modify the field "quantity" of a certain row (element) in the Hash Table.
Do Hash Tables allow to update? I'm surprised my book does not mention any method for updating a Hash Table.
Thank you in advance for any information.put() will replace whatever exists under the specified key, if anything, with whatever new value you put. If you want to modify the contents of an object stored in the hashtable, you'd have to get the object, modify it, and put it back. At least for non-immutable objects you could just get and modify. The modify will modify that object, the reference to it would already exist in the table, so the put is kinda redundant, and would affect performance somewhat (although not noticeable for many apps). This wouldn't work for String or Integer, for example, you'd really just be putting a new String or Integer, so no need for get, just do put. Get it?
Maybe you are looking for
-
How to find out multiple instances of the same application
Hi, Please help me with your Java Networking expertise. Is there any way you could suggest where we could know how many instances of the same application is running in a network ? Sending a UDP packet would require to specify the destination of the m
-
I can't delete a folder in my mailbox.
I have tried to delete it on my ipad, ipod, iphone and computer, none will work. There's no emails in it, and if I do delete it, the next time I sign it it's back. Same thing happens if I try to rename the folder, it switches back after I sign in aga
-
Trouble connecting HP Laserjet 5M to iMac G5
I'm having difficulty hooking up an HP Laserjet 5M to an iMac G5 directly with a crossover ethernet network cable at a friend's house. I've tried resetting the ip address in the control panel of the HP printer, and then adding the printer on the iMac
-
Why can't I turn on Photostream?
I open iPhoto and regardless if I go to the Photostream tab and click "Turn On Photostream" or go to iPhoto Preferences and check "Enable Photostream", nothing happens. The button does it's little animation to acknowledge I clicked it and the check b
-
Is it possible to turn off the magnification animation?
I know my question doesn't clarify anything. I know how to disable the magnification. I quite know Mac deeply, but I want to know if there's a way to "shorten" the magnification animation. The magnification in my Mac has been slow (not slow but it's