Transformation Condition¶

Description¶

The transformation condition feature allows you to execute a defined transformation only if a specified condition is met. The condition must be defined as a boolean expression that evaluates to true or false. Greenmask uses expr-lang/expr under the hood. You can use all functions and syntax provided by the expr library.

You can use the same functions that are described in the built-in transformers

The transformers are executed one by one - this helps you create complex transformation pipelines. For instance depending on value chosen in the previous transformer, you can decide to execute the next transformer or not.

Record descriptors¶

To improve the user experience, Greenmask offers special namespaces for accessing values in different formats: either the driver-encoded value in its real type or as a raw string.

record: This namespace provides the record value in its actual type.
raw_record: This namespace provides the record value as a string.

You can access a specific column’s value using record.column_name for the real type or raw_record.column_name for the raw string value.

Warning

A record may always be modified by previous transformers before the condition is evaluated. This means Greenmask does not retain the original record value and instead provides the current modified value for condition evaluation.

Null values condition¶

To check if the value is null, you can use null value for the comparisson. This operation works compatibly with SQL operator IS NULL or IS NOT NULL.

Is null cond example

record.accountnumber == null && record.date > now()

Is not null cond example

record.accountnumber != null && record.date <= now()

Expression scope¶

Expression scope can be on table or specific transformer. If you define the condition on the table scope, then the condition will be evaluated before any transformer is executed. If you define the condition on the transformer scope, then the condition will be evaluated before the specified transformer is executed.

Table scope

- schema: "purchasing"
  name: "vendor"
  when: 'record.accountnumber == null || record.accountnumber == "ALLENSON0001"'
  transformers:
    - name: "RandomString"
      params:
        column: "accountnumber"
        min_length: 9
        max_length: 12
        symbols: "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ"

Transformer scope

- schema: "purchasing"
  name: "vendor"
  transformers:
    - name: "RandomString"
      when: 'record.accountnumber != null || record.accountnumber == "ALLENSON0001"'
      params:
        column: "accountnumber"
        min_length: 9
        max_length: 12
        symbols: "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ"

Int and float value definition¶

It is important to create the integer or float value in the correct format. If you want to define the integer value you must write a number without dot (1, 2, etc.). If you want to define the float value you must write a number with dot (1.0, 2.0, etc.).

Warning

You may see a wrong comparison result if you compare int and float, for example 1 == 1.0 will return false.

Architecture¶

Greenmask encodes the way only when evaluating the condition - this allows to optimize the performance of the transformation if you have a lot of conditions that uses or (||) or and (&&) operators.

Example: Chose random value and execute one of¶

In the following example, the RandomChoice transformer is used to choose a random value from the list of values. Depending on the chosen value, the Replace transformer is executed to set the activeflag column to true or false.

In this case the condition scope is on the transformer level.

- schema: "purchasing"
  name: "vendor"
  transformers:
    - name: "RandomChoice"
      params:
        column: "name"
        values:
          - "test1"
          - "test2"

    - name: "Replace"
      when: 'record.name == "test1"'
      params:
        column: "activeflag"
        value: "false"

    - name: "Replace"
      when: 'record.name == "test2"'
      params:
        column: "activeflag"
        value: "true"

Example: Do not transform specific columns¶

In the following example, the RandomString transformer is executed only if the businessentityid column value is not equal to 1492 or 1.

  - schema: "purchasing"
    name: "vendor"
    when: '!(record.businessentityid | has([1492, 1]))'
    transformers:
      - name: "RandomString"
        params:
          column: "accountnumber"
          min_length: 9
          max_length: 12
          symbols: "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ"

Example: Check the json attribute value¶

In the following example, the RandomString transformer is executed only if the a attribute in the json_data column is equal to 1.

- schema: "public"
  name: "jsondata"
  when: 'raw_record.json_data | jsonGet("a") == 1'
  transformers:
    - name: "RandomString"
      params:
        column: "accountnumber"
        min_length: 9
        max_length: 12
        symbols: "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ"