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Apply filters

To test specific portions of data for quality, you can apply dynamic filters when you scan data in your warehouse. To do so, you define a filter configuration key in your scan YAML file, then add a variable to the soda scan command that specifies a portion of data for Soda SQL to scan instead of scanning a larger data set. When you add a variable, Soda SQL adds a filter to the WHERE clause of the SQL queries it creates to scan your data. Refer to How Soda SQL works to learn more.

For example, where a CUSTOMER_TRANSACTIONS table has a DATE column, you may wish to run a scan only against the newest data added to the table. In such a case, you can apply a filter for a specific date so that Soda SQL only scans data associated with that date.

$ soda scan -v date=2021-01-12 warehouse.yml tables/customer_transactions.yml

Similarly, if the table has a column for COUNTRY, you can apply a filter that scans only the data that pertains to the country you specify as a variable in the soda scan command.

$ soda scan -v country=FRA warehouse.yml tables/customer_transactions.yml

If you have a Soda Cloud account, you can configure filters in the first step of the guide to Create a monitor.

Configure a filter in Soda SQL

  1. Open the scan YAML file associated with the table on which you want to run filtered scans. The scan YAML files are usually located in the warehouse directory of your Soda SQL project.
  2. To the file, add a filter configuration key as per the following example. Be sure to use quotes for input that is in text format. 
    table_name: CUSTOMER_TRANSACTIONS
filter: "date = DATE '{{ date }}'"
metrics: ...
columns: ...
  3. When you define a variable in your scan YAML file, Soda SQL applies the filter to all tests except tests defined in SQL metrics. To apply a filter to SQL metrics tests, be sure to explicitly define the variable in your SQL query. Refer to Variables in custom metrics
  4. Save the changes to the YAML file, then run a filtered scan by adding a variable to your soda scan command in your command-line interface. 
    $ soda scan -v date=2021-01-12 warehouse.yml tables/customer_transactions.yml

For time-partitioned tables, consider configuring a separate scan YAML file for scans that use a filter. For example:

  • customer_transactions.yml with no filter defined in the file, so you can scan all the data in the table without applying a date filter 
    $ soda scan warehouse.yml tables/customer_transactions.yml
  • customer_transactions_tp.yml with a date filter defined, so you can add a date variable to your soda scan command to scan against a date you specify 
    $ soda scan -v date=2021-01-12 warehouse.yml tables/customer_transactions_tp.yml

Configure a filter in a programmatic scan

Alternatively, you can use variables when programmatically invoking a Soda SQL scan. Refer to Configure programmatic scans.

  1. Follow steps 1 - 3 above to prepare your scan YAML file.
  2. Configure your programmatic scan to include variables as per the following example.
scan_builder = ScanBuilder()
scan_builder.warehouse_yml_file = 'warehouse.yml'
scan_builder.scan_yml_file = 'tables/my_table.yml'
scan_builder.variables = {
    'date': '2021-06-12'
}
scan = scan_builder.build()
scan_result = scan.execute()
if scan_result.has_test_failures():
    print('Scan has test failures, stop the pipeline')

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Last modified on 16-Jul-21

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