topic Re: Qlikview buffer load in QlikView

Qlikview buffer load

singhcv123 — Fri, 20 Nov 2020 18:02:30 GMT

Hi Please any one share the qlikview buffer load example .....

Re: Qlikview buffer load

Tue, 06 May 2014 08:49:46 GMT

hi look at the link below

http://www.youtube.com/watch?v=1K7_WyksYxs

Re: Qlikview buffer load

ashfaq_haseeb — Tue, 06 May 2014 08:50:49 GMT

Hi,

Please find the below result from QlikView help.

Buffer

QVD files can be created and maintained automatically via the buffer prefix. This prefix can be used on most Load and Select (SQL) statements in script. It indicates that QVD Files are used to cache/buffer the result of the statement.

Numerous limitations exist, most notable is that there must be either a file load or a select statement at the core of any complex statement.

The name of the QVD file is a calculated name (a 160-bit hexadecimal hash of the entire following load or select statement and other discriminating info) and is typically stored in the Application Data folder or another folder specified under User Preferences: Locations. This means that the QVD buffer will be rendered invalid by any change in the following load or select statement.

QVD buffers will normally be removed when no longer referenced anywhere throughout a complete script execution in the document that created it or when the document that created it no longer exists. This housekeeping can be turned off by checking the options Keep Unreferenced QVD Buffers in Document Properties: General (first requirement) and Keep Orphaned QVD Buffers in User Preferences (second requirement) property pages respectively, though the procedure cannot be generally recommended.

The syntax is:

buffer[ (option [ , option] ) ] ( loadstatement | selectstatement )

where:

option ::= incremental | expiry

expiry::= stale [after]amount[ (days | hours)]

amount is a number specifying the time period. Decimals may be used. The unit is assumed to be days if omitted.

The incremental option enables the ability to read only part of an underlying file. Previous size of the file is stored in the XML header in the QVD file. This is particularly useful with log files. All records loaded at a previous occasion are read from the QVD file whereas the following new records are read from the original source and finally an updated QVD-file is created. Note that the incremental option can only be used with load statements and text files and that incremental load cannot be used where old data is changed or deleted!

The stale after option is typically used with DB sources where there is no simple timestamp on the original data. Instead one specifies how old the QVD snapshot can be to be used. A stale after clause simply states a time period from the creation time of the QVD buffer after which it will no longer be considered valid. Before that time the QVD buffer will be used as source for data and after that the original data source will be used. The QVD buffer file will then automatically be updated and a new period starts.

If no option is used, the QVD buffer created by the first execution of the script will be used indefinitely.

Examples:

buffer SQL SELECT * FROM MyTable;

buffer (stale after 7 days) SQL SELECT * FROM MyTable;

buffer (incremental) LOAD * FROM MyLog.log;

Back to Script Statements and Keywords.

Regards

ASHFAQ

Re: Qlikview buffer load

Tue, 06 May 2014 08:51:18 GMT

hi look at this

QVD files can be created and maintained automatically via the buffer prefix. This prefix can be used on most Loadand Select (SQL) statements in script. It indicates that QVD Files are used to cache/buffer the result of the statement.

Numerous limitations exist, most notable is that there must be either a file load or a select statement at the core of any complex statement.

The name of the QVD file is a calculated name (a 160-bit hexadecimal hash of the entire following load or selectstatement and other discriminating info) and is typically stored in the Application Data folder or another folder specified under User Preferences: Locations. This means that the QVD buffer will be rendered invalid by any change in the following load or select statement.

The syntax is:

buffer[ (option [ , option] ) ] ( loadstatement | selectstatement )

where:

option ::= incremental | expiry

expiry::= stale [after]amount[ (days | hours)]

amount is a number specifying the time period. Decimals may be used. The unit is assumed to be days if omitted.

If no option is used, the QVD buffer created by the first execution of the script will be used indefinitely.

Examples:

buffer select * from MyTable;

buffer (stale after 7 days) select * from MyTable;

buffer (incremental) load * from MyLog.log;

Re: Qlikview buffer load

Wed, 15 Oct 2014 02:39:51 GMT

Hi, Can you please give a clarification when why and where we are going to use this buffer load

Re: Qlikview buffer load

Wed, 15 Oct 2014 04:34:36 GMT

Hi,

Can you please give a clarification when why and where we are going to use this buffer load

As answer by you give me an idea about buffer load but the thing is

1. Buffer Select * from MyTable;

It will create a QVD in Apps folder Or we can use a defined path which is nothing but a cache file. why we are going with Buffer key word instead of that

table1:

Select * from MyTable;

store table1 into <Path>/Table.qvd;

2. Buffer (stale after 7 days) select * from Mytable;

the result is it will reload the data after the 7th day why can we use incermental Load by using triggers with assining some specified time

Re: Qlikview buffer load

ganeshsvm — Wed, 07 Dec 2016 08:11:33 GMT

Buffer LOAD: It stores QVD in temp folder and is used to improve reload time by fetching data from a temporary qvd.

There is no comparison between Buffer Load and incremental load

Buffer load will not fetch latest data; it will only fetch data from a temporary QVD which is created during first Buffer Load.

Buffer load does not match rows with the database, it will only check for number of columns and column names.

This video shows a simple example of Buffer load and its diff options.

https://www.youtube.com/watch?v=aMrrEC3QOFg