Partial reload

A full reload always starts by deleting all tables in the existing data model, and then runs the load script.

A partial reload will not do this. Instead it keeps all tables in the data model and then executes only Load and Select statements preceded by an Add, Merge, or Replace prefix. Other data tables are not affected by the command. The only argument denotes that the statement should be executed only during partial reloads, and should be disregarded during full reloads. The following table summarizes statement execution for partial and full reloads.


Statement	Full reload	Partial reload
Load ...	Statement will run	Statement will not run
Add/Replace/Merge Load ...	Statement will run	Statement will run
Add/Replace/Merge Only Load ...	Statement will not run	Statement will run

Partielle Ladevorgänge haben im Vergleich zu vollständigen Ladevorgängen mehrere Vorteile:

Sie sind schneller, da nur die kürzlich geänderten Daten geladen werden müssen. Bei großen Datensätzen ist der Unterschied signifikant.
Es wird weniger Speicher verbraucht, da weniger Daten geladen werden.
Der Vorgang ist zuverlässiger, da Abfragen an Datenquellen schneller ausgeführt werden, was das Risiko von Netzwerkproblemen reduziert.

Damit der partielle Ladevorgang korrekt funktioniert, muss die App mit Daten geöffnet werden, bevor der partielle Ladevorgang ausgelöst wird.

Führen Sie einen partiellen Ladevorgang durch, indem Sie die Schaltfläche Laden nutzen. Weitere Informationen finden Sie unter Button. Sie können auch das Qlik Engine JSON API verwenden.

Limitations

A partial reload will fail if there are commands with references to tables that existed during full reload, but not during partial reload.

Example commands

LEFT JOIN(<Table_removed_after_full_reload>)

CONCATENATE(<Table_removed_after_full_reload>)

Where <Table_removed_after_full_reload> is a table that existed in full reload, but not in partial reload.

Workaround

As a workaround you can surround the command with following if-statement:

IF NOT IsPartialReload() THEN ... ENDIF.

A partial reload can remove values from the data. However, this will not be reflected in the list of distinct values, which is a table maintained internally. So, after a partial reload, the list will contain all distinct values that have existed in the field since the last full reload, which may be more than what currently exists after the partial reload. This affects the output of the FieldValueCount() and the FieldValue() functions. The FieldValueCount() could potentially return a number greater than the current number of field values.

Example 1

Load script

Add the example script to your app and do a partial reload. To see the result, add the fields listed in the results column to a sheet in your app.

T1:
Add only Load distinct recno()+10 as Num autogenerate 10;

Result

Resulting table
Num	Count(Num)
11	1
12	1
13	1
14	1
15	1
16	1
17	1
18	1
19	1
20	1

Explanation

The statement is only executed during a partial reload. If the "distinct" prefix is omitted, the count of the Num field will increase with each subsequent partial reload.

Example 2

Load script

Add the example script to your app. Do a full reload and view the result. Next, do a partial reload and view the result. To see the results, add the fields listed in the results column to a sheet in your app.


T1:
Load recno() as ID, recno() as Value autogenerate 10;

T1:
Replace only Load recno() as ID, repeat(recno(),3) as Value autogenerate 10;

Result

Output table after full reload
ID	Value
1	1
2	2
3	3
4	4
5	5
6	6
7	7
8	8
9	9
10	10

Output table after partial reload
ID	Value
1	111
2	222
3	333
4	444
5	555
6	666
7	777
8	888
9	999
10	101010

Explanation

The first table is loaded during a full reload and the second table simply replaces the first table during a partial reload.

Weitere Informationen

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