Created
September 2, 2022 06:36
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PIpeRider custom assertion to allow a specific number of null values in a column
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| class AssertAllowedNulls(BaseAssertionType): | |
| def name(self): | |
| return "assert_allowed_nulls" | |
| def execute(self, context: AssertionContext, table: str, column: str, metrics: dict) -> AssertionResult: | |
| column_metrics = metrics.get('tables', {}).get(table, {}).get('columns', {}).get(column) | |
| if column_metrics is None: | |
| # column could not be found | |
| return context.result.fail('column does not exist') | |
| # 1. Get the metric for the desired column, e.g. num of nulls in column | |
| nulls = column_metrics.get('nulls') | |
| # 2. Get expectation from assertion file | |
| allowed_nulls = context.asserts.get('allowed_nulls', []) | |
| # 3. Implement logic to compare expectated and actual metic value | |
| if (nulls <= allowed_nulls): | |
| # 4. return pass (acceptable number of nulls) | |
| return context.result.success("{}".format(nulls)) | |
| else: | |
| # 4. return fail (more nulls than we expected) | |
| return context.result.fail("{}".format(nulls)) | |
| def validate(self, context: AssertionContext) -> ValidationResult: | |
| result = ValidationResult(context) | |
| # result.errors.append('explain to users why this broken') | |
| return result | |
| # register new assertions | |
| register_assertion_function(AssertAllowedNulls) |
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