Airflow

Doing data quality checks using the SQLCheckOperator

How to use SQLCheckOperator to verify that the database contains an expected number of rows

Bartosz Mikulski 20 Oct 2020 – 1 min read

SQLCheckOperator is an Airflow operator that executes a SQL query, expects to receive a single row in the response, and attempts to cast every value in the row to a boolean. It succeeds when all returned values can be cast to true, so the query may return those values:

a boolean True
a non-zero numeric value (including negative values!)
a non-empty string
a non-empty list, set, or dictionary

In addition to failing when any of the values is False, the SQLCheckOperator operator also fails when the query returns no rows.

For example, we can use that operator to check the count of values in a table:

from airflow.operators.sql import SQLCheckOperator

operator = SQLCheckOperator(
     sql="SELECT COUNT(*) FROM some_table WHERE some_column='{{ yesterday_ds_nodash }}'"
)