Using Change Schema to remap data property keys - Amazon Glue
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Using Change Schema to remap data property keys

A Change Schema transform remaps the source data property keys into the desired configured for the target data. In a Change Schema transform node, you can:

  • Change the name of multiple data property keys.

  • Change the data type of the data property keys, if the new data type is supported and there is a transformation path between the two data types.

  • Choose a subset of data property keys by indicating which data property keys you want to drop.

You can also add additional Change Schema nodes to the job diagram as needed – for example, to modify additional data sources or following a Join transform.

Using Change Schema with decimal datatype

When using the Change Schema transform with decimal datatype, the Change Schema transform modifies the precision to the default value of (10,2). To modify this and set the precision for your use case, you can use the SQL Query transform and cast the columns with a specific precision.

For example, if you have an input column named "DecimalCol" of type Decimal, and you want to remap it to an output column named "OutputDecimalCol" with a specific precision of (18,6), you would:

  1. Add a subsequent SQL Query transform after the Change Schema transform.

  2. In the SQL Query transform, use an SQL query to cast the remapped column to the desired precision. The SQL query would look like this:

    SELECT col1, col2, CAST(DecimalCol AS DECIMAL(18,6)) AS OutputDecimalCol FROM __THIS__

    In the above SQL query:

    • `col1` and `col2` are other columns in your data that you want to pass through without modification.

    • `DecimalCol` is the original column name from the input data.

    • `CAST(DecimalCol AS DECIMAL(18,6))` casts the `DecimalCol` to a Decimal type with a precision of 18 digits and 6 decimal places.

    • `AS OutputDecimalCol` renames the casted column to `OutputDecimalCol`.

By using the SQL Query transform, you can override the default precision set by the Change Schema transform and explicitly cast the Decimal columns to the desired precision. This approach allows you to leverage the Change Schema transform for renaming and restructuring your data while handling the precision requirements for Decimal columns through the subsequent SQL Query transformation.

Adding a Change Schema transform to your job


The Change Schema transform is not case-sensitive.

To add a Change Schema transform node to your job diagram
  1. (Optional) Open the Resource panel and then choose Change Schema to add a new transform to your job diagram, if needed.

  2. In the node properties panel, enter a name for the node in the job diagram. If a node parent isn't already selected, choose a node from the Node parents list to use as the input source for the transform.

  3. Choose the Transform tab in the node properties panel.

  4. Modify the input schema:

    • To rename a data property key, enter the new name of the key in the Target key field.

    • To change the data type for a data property key, choose the new data type for the key from the Data type list.

    • To remove a data property key from the target schema, choose the Drop check box for that key.

  5. (Optional) After configuring the transform node properties, you can view the modified schema for your data by choosing the Output schema tab in the node details panel. The first time you choose this tab for any node in your job, you are prompted to provide an IAM role to access the data. If you have not specified an IAM role on the Job details tab, you are prompted to enter an IAM role here.

  6. (Optional) After configuring the node properties and transform properties, you can preview the modified dataset by choosing the Data preview tab in the node details panel. The first time you choose this tab for any node in your job, you are prompted to provide an IAM role to access the data. There is a cost associated with using this feature, and billing starts as soon as you provide an IAM role.