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Create Flow Parameter

At the flow level, you can define flow parameters to reference in your recipes. A flow parameter is a (Variable) value or a set of enumerated values (Selector type).

注意

Flow parameters apply to recipe steps only.

  • 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.

    提示

    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 Parameters.

  3. In the Manage Parameters dialog, click the Parameters tab.

  4. Click Add parameter.

  5. Enter a Name for your parameter.

    注意

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

  6. (optional) Specify a user-friendly Description value.

  7. For Type, select the type of parameter. See below.

Variable type parameter

Variable type parameters are single values that can be one of the following formats:

Format

Example

String

Here is my String value.

Alteryx patterns

Any string of letters:

`{letter}+`

regular expression

Any string of letters:

/[a-zA-z]+/

Additional steps:

  1. Enter a default value for this parameter.

    注意

    Input Values are evaluated as String type.

  2. Click Save.

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

Selector type parameter

Selector type parameters are lists of one or more permitted values.

Additional steps:

  1. Under Choices, enter a value.

    提示

    The first value that you add is the default value.

  2. Click Add.

  3. Repeat the above steps until all permitted values have been added.

  4. 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.

Parameter name

Valid references

Notes

paramRegion
$paramRegion
${paramRegion}

Both references are valid.

param Region
${param Region}

注意

If the parameter name contains a space, the curly brackets are required. As a matter of habit, you might want to use the curly brackets for all parameter references. This syntax also helps to distinguish your named parameters from metadata references, which are fixed. See Source Metadata References.

Apply Parameter Override

注意

Parameter overrides that were defined in a pre-Release 7.1 version of the software now appear in the Overrides tab.

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.

注意

You can apply override values for any parameter of any type that is referenced in the flow: dataset parameters, flow parameters, and object parameters.

注意

For selector type flow parameters, the override value must be a value from the defined list of values.

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

    注意

    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.

提示

Through Flow View, overrides can also be applied to the recipe parameters that are included when flow tasks are executed as part of a plan.

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.

注意

When a parameter value is displayed in a column, the column type in the data grid may be correctly inferring the type to your desired data type. However, the underlying type is still String type. To convert the underlying type, you must use one of the PARSE functions on your String values.

Variable type 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:

Setting

Value

Notes

Name
paramRegionId

Note the more appropriate name.

Value
0

In this case, there is no region identifier value 0. You choose to set the default to a value that is valid for the target data type (Integer) but is invalid for the scope of the data itself.

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:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

PARSEINT(${paramregionId})

Parameter: New column name

paramRegionId

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.

Variable type 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:

Setting

Value

Notes

Name
paramDate

Note the more appropriate name.

Value

In this case, the value is left empty to be overridden as needed in the application with the current timestamp.

You should decide on the expected values for this parameter, as you must apply them to:

  • Parameter overrides

  • Recipe steps (e.g PARSEDATE function parameters)

It may be easier to insert the format string here as the default value. For example:

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:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

PARSEDATE(${paramDate},['yyyy-mm-dd HH:MM:SS'])

Parameter: New column name

paramDate

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

提示

You could also overwrite invalid values in the following manner. However, that may mask problems with your inserted values.

Transformation Name

Edit column with formula

Parameter: Columns

execDate

Parameter: Formula

IF((execDate == '') || ISNULL(execDate), NOW('UTC'), execDate)

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.

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

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

DATEFORMAT(execDate, 'HH:MM:SS')

Parameter: New column name

Time

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

Variable type example - parameter with range of values

Suppose you need to create a parameter that can contain any two-digit value from 0 to 99. To do so, you create a flow parameter of variable type, using a Wrangle as the value:

`{digit}{digit}`

The above matches two-digit values only. It does not match single-digit values. To expand the pattern to also match single digit values, you can use this one:

`({digit}|{digit}{digit})`

  • Note how the value is specified using backticks (`), which are used to indicate a Wrangle .

  • The vertical bars are delimiters to separate the values, when they are processed within the application.

This parameter now accepts the following values:

0-9
00-99

Selector type example - parameter with multiple values

Suppose you wish to create a flow parameter that can contain one of multiple values for color. Typically, you must track these values through an array, such as the following containing a set of colors:

["red","white","blue","black"]

Using a selector type of flow parameter, you can specify these values as choices in your permitted values list for the $myColors flow parameter:

red
white
blue
black

In this scenario, red is the default value.

Within your recipe, you can test for the presence of a parameter value. In the following transformation, a value of true is set in the new column isBlue if the value of $myColors is blue:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

F($myColors == "blue",true,false)

Parameter: New column name

'isBlue'

提示

When you reference a selector type flow parameter in a transformation step, you are presented the set of accepted values from which you apply the preferred one.

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 Task - Run Job.

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