At the flow level, you can define flow parameters to reference in your recipes. A flow parameter is a variable that is assigned a String value. 

• To flow parameters and parameters of other types, you can apply override values at the flow level through the same interface. Details are below.
• For more information on flow parameters, see Overview of Parameterization.

Limitations

• Flow parameters are of String data type.
  
  

  Tip
  Tip: You can wrap flow parameter references in your transformations with one of the PARSE functions. See "Examples" below.

• Flow parameters are converted to constants in macros. Use of the macro in other recipes results in the constant value being applied.

Limitations on usage

A flow parameter cannot be used in the following transformation steps or fields.

Transformations:

• Rename columns: Cannot use a flow parameter as a new column name.

Transformation fields:

• The as clause when creating a New formula transformation. 

Create Parameter

Steps:

1. Open the flow where you wish to apply the flow parameter. 
2. From the Flow View context menu, select Manage parameters.....
3. In the Manage Parameters dialog, click the Parameters tab. 
4. Click Add parameter.

5. Enter a Name for your parameter.
   
   

   Info
   NOTE: Name values are case-sensitive. After saving a flow parameter, its name cannot be changed.

6. Enter a default value for this parameter.

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   NOTE: Input Values are evaluated as String type.

7. Click Save.

The parameter is available for use in any recipe in your flow. See "Use Parameter."

Parameter Names

Parameter names can contain alphanumeric characters and spaces. in the following table, you can see how parameter names must be referenced in recipe steps. 

$paramRegion
${paramRegion}

${param Region}

Apply Parameter Override

You can apply overrides to all parameter types, including flow parameters, at the flow level. An overridden value applies to all references of the parameter within the flow.

• Upstream parameter values: Parameter values can be inherited from upstream recipes and datasets. 
  
  

  Info
  NOTE: Override values applied in a downstream flow are applied to the upstream flow when its objects are invoked for purposes of generating data for use in the downstream flow.

•  Downstream parameter values: Downstream flows receive parameter values, default or overridden, from upstream flows. These values can be overridden at the flow level.

Steps:

1. Open the flow where you wish to apply the flow parameter. 
2. From the Flow View context menu, select Manage parameters.....
3. In the Manage Parameters dialog, click the Overrides tab. 
4. Click Add override.

5. Select the parameter to override from the drop-down list.

6. Set the override value for this flow. Click Save.

7. Click Save.

This override value is applied to all references to the parameter in the flow. 

Override Evaluation

Override values can be applied in multiple locations. Parameter values are evaluated in the following order of precedence (highest to lowest):

1. Overrides at run-time in the Run Job page.
2. Overrides at the flow level.
3. Default values for the flow. 
4. Inherited values from upstream flows.

For more information, see Overview of Parameterization.

Use Parameter

In your recipe step, you can add references to your flow parameter in the following format:

${MyRecipeParameter}

In a recipe, flow parameters can be applied to:

• Function parameters
• Replacements for String values

Examples

Below are examples of how to use flow parameters.

Example - String parameter

In this example, data is segmented by time zone. You must create a parameter to capture the following U.S. time zones, which must be specified explicitly:

'Hawaii'
'Alaska'
'Pacific'
'Mountain'
'Central'
'Eastern'

In your flow, you create the following flow parameter:

In the following transformation, the parameter value is inserted into a new column, paramTZ in your dataset:

You can also use the parameter as an input to a function. In the following example, the paramTimeZone parameter is merged with the values in the Store_Nbr to compute primary key storeId field:

Example - Integer parameter

Instead of segmenting the data by named time zone values, suppose your data is segmented by regions, which are numeric in number. Your flow parameter definition could look like the following:

To use this flow parameter as an integer, you must reference it wrapped in the PARSEINT function, which evaluates the input value against the Integer data type:

In the column histogram for the paramRegionId column, you can verify that the value 0 is present. Set an override outside at the flow level to insert a different value in the column. 

For more information, see PARSEINT Function.

Example - Date parameter

Suppose you need to be able to pass a date into the execution of a recipe. If no date is passed in, then the current time is used. The variable is declared as follows:

Instead of segmenting the data by named time zone values, suppose your data is segmented by regions, which are numeric in number. Your flow parameter definition could look like the following:

yyyy-mm-dd HH:MM:SS

You can use the following to insert the parameter value into your dataset. Note that the value is initially inserted as a String value, so the PARSEDATE function is used as a wrapper:

For more information, see PARSEDATE Function.

If the inserted value is empty or null, you can insert the current timestamp:

In the above, the value in execDate is tested to see if it is either:

• empty
• null

If so, the output of the NOW function is written. By default, this function returns the timestamp value at UTC time. 

If there is a valid value, then it is written back to the column.

See NOW Function.

You can use the following to extract the time value from the parsed date param:

Since this value is not the parameter value specifically, the column name was listed simply as Time.

Apply Parameter Override via API

When you run a job via the APIs, you can apply parameter overrides to the following parameter types:

• dataset parameters
• output parmeters
• flow parameters

For more information, see API Workflow - Run Job.