visual composer - paging records - using sql to get chunks of data _ scn

20/2/2014 Paging records - Using SQL to get Chunks of Data | SCN

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created by Ehud Nir on Feb 17, 2014 1:26 PM, last modif ied by Ehud Nir on Feb 19, 2014 9:54 AM

Abstract & MotivationThis example shows yet another way to allow paging behavior for our application. Here it is achieved using a Data

Service that returns a subset of the data: For each Next / Previous press by the user we call the data service to get the

relevant chunk of rows.

For example, for the input:

Start index: 6

Number of records: 5

The result is a list containing the rows 6 to 10.

One big advantage of this method: The application does not need to handle big amounts of data. The other benefit

we see soon.

Related documents:

Paging records in the UI

Paging records in the UI - Coding our own Web Service to get Row Numbers

The applicationFirst five records:

After pressing Next:

The Backend - SQL ExampleOur data service consists of a simple SQL Query.

Input parameters:

@start - start index

@step - number of rows

Result: the requested subset of the Suppliers table.

Code specifics:

Step 1: The inner SELECT statement return the Suppliers data with an additional column called row, for

the row number (1, 2, 3...).

Step 2: The outer SELECT filters part of Step 1 result, using the input parameters @start and @step

Paging records - Using SQL to get Chunksof Data

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against the row column.

Modeling1. Search for the relevant data service and add it to the model.

2. In case it is a JDBC Stored Procedure, as shown here:

- Right click => Test Data Service.

- Enter input value and press Text.

- Press Add Fields to have the fields in the output port.

3. Add a Table View from the output of the service.

4. Add a Data Share element.

5. Connect the Data Share to the service, edit the link to "listen" to the "*get" event (we model its triggering in later

steps).

6. Add two fields to the Data Share, index and step, as follows:



7. Define the field assigns in the Mapping link. Here we pass our SQL code the starting index and number of rows:

8. Go to the Layout Board and define the Actions for the "First" button:

- ASSIGN to reset to the first chunk of records.

- GET as a Custom Action to activate the data service (see in step 5 where we define the link activation event).

9. Define the "Previous" button: Subtract the step size from the current index:



10. Define the Enabled condition for the "Previous" button, adding the step size to the index:

11. In quite the same way, define the "Next" button:

That's it. This solution involved:

A bit of SQL coding.

A super-simple VC model.

Benefit #2 (in addition to having No Big Data): Note how simple the modeling is comparing to the other paging

solution:

The Filter Operator is gone, as filtering is done on the database.

Also gone is the Data Share.

Possibly an additional Web Service to get the row number to rely on is gone as well - we don't need logic

depending on row numbers here.

Related documents:

Paging records in the UI

Paging records in the UI - Coding our own Web Service to get Row Numbers

100 View s Categories: SAP Visual Composer 7.1 and Above Topics: performance, database Tags: code, sql, paging



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