Implementing Input Parameters

The figure, Input Parameter Types, shows the different types of Input Parameters that can be defined.

The Direct parameter type can be combined with a semantic type such as Date, Currency, or Unit of measure. This means that the value help will be based on these types of values. For example, if you specify Date, then a popup calendar will appear for the user prompt. If you specify Currency, then a list of valid currencies will be presented in the value help. This allows us to provide flexible input for the user, but it also allows us to control the type of values that are allowed.

For the Currency and Unit of measure semantic types, the list of proposed values will be created based on the corresponding reference tables in SAP HANA. This setup requires that the default schema assigned to the view contains the reference tables.

Input parameters support multiple values. This means that, at runtime, the end user has the possibility to provide several values to the parameter. Some examples of use cases include the following:

• Applying filters of the types List of values and Not in List

• Expression of calculated columns and expression of filters in projection nodes, provided that the expression requires a multi-value input

When you define an input parameter of the type, Derived from Procedure/Scalar Function, it is possible to map parameters to the input of the scalar function or procedure.

Note

Input parameters of the types Derived from table and Derived from Procedure/Scalar Function do not generate a prompt for the end user (they pass the parameter values directly), except if you select the Input Enabled option. In this case, the values returned by the table, procedure, or scalar function, can be modified by the end user.

Upon the execution of the calculation view, input parameters are passed inside the SQL query using a PLACEHOLDER clause - for example:

SELECT <columns> FROM <calculation_view_name> (placeholder."$$IP_YEAR$$"=>'2019') GROUP BY <group_by columns>;

Not all applications are able to pass values to the PLACEHOLDER. That is why sometimes you must use variables to achieve the same outcome.

Note

When you have defined an input parameter, you must then use it in an expression. Otherwise, it is ignored.

As discussed already, unlike a variable, an input parameter can be used in a conditional expression. For example, we can use an input parameter to determine which measure should be displayed in a particular column.

To illustrate this, we create a calculated column called AMOUNT, which can be filled with either the gross amount or the net amount, depending on the value that the user chooses when querying the view.

In our example, we have chosen to use an input parameter of the type Static List. This means that we predefine the allowed value that can be chosen by the user in a list. This is fine for short lists but, when the list becomes large, it becomes cumbersome to manage because you would have to edit the calculation view and rebuild it each time. Of course, you could choose the type Direct, which would mean the user could input anything. However, that would mean that apart from the user not having any guidance, he/she could also mistype the value, or enter the value in the wrong format (perhaps adding leading zeros when they were not required).

A good solution would be to define the input parameter with the type Column and then, in the View / Table Value Help, enter the name of a table or view where the allowed entries are presented. This also means that this list can be used by multiple input parameters and encourages central maintenance of the consistent, allowed values list.

An input parameter used within a formula does not necessarily have to be of the type Static List. For example, it can also be a Direct numeric value used in multiplication or any other calculation type.

In the example in the figure, Calling an Input Parameter in a Calculation, if the user selects GROSS, the calculated column (of type Measure) will display the GROSS_AMOUNT measure in the AMOUNT column. Any other selection will result in NET_AMOUNT being displayed.

In the figure, Using a Calendar Dialog for Date Input Parameters, the user is asked for a single value. Dates can also be selected as ranges.

Note

SAP recommends using input parameters instead of variables whenever possible, because input parameters provide more flexibility and features than variables. However, some front-end tools cannot process input parameters and so variables must be used.

In many cases, calculation views use other calculation views as data sources. This is not necessarily confined to two levels; we can go on and layer the calculation views to create a stacked model. When you execute a calculation view in which variables or input parameters are defined, it is possible to pass their values (entered by the end user at runtime) to the lower level calculation views. In fact, the input parameters and variables at the lower levels are usually ignored unless you define input parameters and variables at the top level and map them to the input parameters and variables in the lower levels. This is called parameter mapping and is an important feature of SAP HANA calculation view modeling.

To enable parameter mapping, you must use the Input Parameter/Variables Mapping feature. You can find this feature in the Parameters tab in the calculation view.

When you open the mapping pane, you must first select the type of mapping you want to work with using the dropdown selector.

There are four types of parameter mapping and you choose the type from the Manage Mapping pane.

When you make your type selection, you will then see (on the left side) the input parameters and variables that are defined in the calculation views from all lower layers in the stack, which are related to the mapping type you selected. On the right side, you will see the input parameters and variables that are defined in the current calculation view (the one you are editing).

Note

You can only map Variables to Variables and Input Parameters to Input Parameters. Cross-Mapping (such as an Input Parameter to a Variable) is not possible.

You simply drag a line between the left and right side to map them. There is also an auto-map feature which means that if the names are the same, the mapping is done with a single click. The auto-map feature generates the input parameters or variables for the current view with the same name as the source variables and also maps them. This means that you do not have to manually create the input parameters or variables in the current view.

Pushing filters down to the source views using parameter mapping is a common scenario. To enable this, choose the type Data Sources from the dropdown list in the Manage Mapping dialog.

Hint

Mapping parameters of the current view to the parameters of the underlying data sources moves the filters down to the underlying data sources during runtime, which reduces the amount of data transferred across them. This is a great way to improve performance.

Another common scenario is when you want to push parameters down from the main calculation view to a calculated column in a lower view to support a calculation. Again, this would be the type Data Sources.

Note that in the type of mapping Data Source, you only map input parameters to input parameters. In other words, a Variable defined in an underlying Calculation View cannot be mapped to a Variable defined in the current Calculation View. However, it is possible to access these variables from the Extract Semantics feature and copy them to the current view. To do that, you right-click the data source in the calculation scenario and choose Extract Semantics. Then choose the Variables tab and select the ones you want to copy to the semantics of your Calculation View.

If a data source for your calculation view is an SQL view and the SQL view requires parameters, you can provide the values from input parameters of the consuming calculation view.

This technique is often used to push down the filters down to the SQL view in order to reduce the workload of the Calculation View.

Note

Mapping Input Parameters from SQL views is possible from SAP HANA QRC 4/2021 QRC onwards.

From SAP HANA Cloud QRC 1/2022 onwards, it is possible to pass input parameters from a Calculation View to an SQL View or a Calculation View that is accessed remotely as a Virtual Table. This ensures that filters are pushed down and executed as close to the data sources as possible.

This new feature requires Smart Data Access (SDA), relying on the odbc adapter – it is not possible with remote sources accessed through the Smart Data Integration (SDI) adapter. The scenario supports remote SAP HANA databases running on SAP HANA Cloud, or SAP HANA On-Premise version 2.0 minimum.

Note

Besides, in SAP HANA On-Premise, Input Parameters in SQL Views are supported only from version 2.0 SPS02 onwards.

Another important use case for mapping input parameters and variables is to enable dynamic value help views.

When you define input parameters and variables, the default data source that generates the value help list is taken from the calculation view itself. So, essentially you are getting an unrestricted list of all possible values to choose from. However, you can also redirect the value help to use a list from another table or view. The main reason we do this is to expose a restricted value help list.

This is also good practice for performance because the value help is not competing with the main calculation view for data. For example, you could create a calculation view on a table that contains all possible cities. Here, your calculation view would include a fixed filter expression that restricts the cities to a specific country. This means that the value help list presents only cities of a specific country to the user.

What if you wanted to change the country? You could go back to the calculation view and change the fixed filter expression, but this would be inefficient.

What we should do is replace the fixed value in the filter expression with a variable based on country. Then, we should map this variable to a variable we define in the main calculation view for the country. This means that when a user is prompted for a country in the main view, the value chosen is passed through the mapping to the value help calculation view, so that the cities are filtered by the country that was chosen. The list of cities is then presented as the value help for the cities column. This is also known as cascading prompts. Cascading is not restricted to two levels; you can also cascade prompts across multiple levels. For example, you could prompt for Continent, which then restricts the list of Countries, which in turn restricts the list of Cities, and so on.

To implement value help parameter mapping, you must select the option Views for value help for variables/input parameters from the dropdown list in the Manage Mapping dialog.

Note

An external view based on a hierarchy could also be considered as a value help cascading solution, and might be more visually appealing to the user.