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Data Validations

Creating a data validator for a JSON file.

Example data validation report

Requirements

  • 5 minutes
  • Git
  • Gradle
  • Docker

Get Started

First, we will clone the data-caterer-example repo which will already have the base project setup required.

git clone git@github.com:data-catering/data-caterer-example.git

Data Setup

To aid in showing the functionality of data validations, we will first generate some data that our validations will run against. Run the below command and it will generate JSON files under docker/sample/json folder.

./run.sh JsonPlan

Plan Setup

Create a new Java or Scala class.

  • Java: src/main/java/io/github/datacatering/plan/MyValidationJavaPlan.java
  • Scala: src/main/scala/io/github/datacatering/plan/MyValidationPlan.scala

Make sure your class extends PlanRun.

import io.github.datacatering.datacaterer.java.api.PlanRun;
...

public class MyValidationJavaPlan extends PlanRun {
    {
        var jsonTask = json("my_json", "/opt/app/data/json");

        var config = configuration()
                .generatedReportsFolderPath("/opt/app/data/report")
                .enableValidation(true)
                .enableGenerateData(false);

        execute(config, jsonTask);
    }
}

import io.github.datacatering.datacaterer.api.PlanRun
...

class MyValidationPlan extends PlanRun {
  val jsonTask = json("my_json", "/opt/app/data/json")

  val config = configuration
    .generatedReportsFolderPath("/opt/app/data/report")
    .enableValidation(true)
    .enableGenerateData(false)

  execute(config, jsonTask)
}

As noted above, we create a JSON task that points to where the JSON data has been created at folder /opt/app/data/json . We also note that enableValidation is set to true and enableGenerateData to false to tell Data Catering, we only want to validate data.

Validations

For reference, the schema in which we will be validating against looks like the below.

.schema(
  field.name("account_id"),
  field.name("year").`type`(IntegerType),
  field.name("balance").`type`(DoubleType),
  field.name("date").`type`(DateType),
  field.name("status"),
  field.name("update_history").`type`(ArrayType)
    .schema(
      field.name("updated_time").`type`(TimestampType),
      field.name("status").oneOf("open", "closed", "pending", "suspended"),
    ),
  field.name("customer_details")
    .schema(
      field.name("name").expression("#{Name.name}"),
      field.name("age").`type`(IntegerType),
      field.name("city").expression("#{Address.city}")
    )
)

Basic Validation

Let's say our goal is to validate the customer_details.name field to ensure it conforms to the regex pattern [A-Z][a-z]+ [A-Z][a-z]+. Given the diversity in naming conventions across cultures and countries, variations such as middle names, suffixes, prefixes, or language-specific differences are tolerated to a certain extent. The validation considers an acceptable error threshold before marking it as failed.

Validation Criteria
  • Field to Validate: customer_details.name
  • Regex Pattern: [A-Z][a-z]+ [A-Z][a-z]+
  • Error Tolerance: If more than 10% do not match the regex, then fail.
Considerations
  • Customisation
    • Adjust the regex pattern and error threshold based on your specific data schema and validation requirements.
    • For the full list of types of basic validations that can be used, check this page.
  • Understanding Tolerance
    • Be mindful of the error threshold, as it directly influences what percentage of deviations from the pattern is acceptable.
validation().col("customer_details.name")
    .matches("[A-Z][a-z]+ [A-Z][a-z]+")
    .errorThreshold(0.1)                                      //<=10% failure rate is acceptable
    .description("Names generally follow the same pattern"),  //description to add context in report or other developers

validation.col("customer_details.name")
  .matches("[A-Z][a-z]+ [A-Z][a-z]+")
  .errorThreshold(0.1)                                      //<=10% failure rate is acceptable
  .description("Names generally follow the same pattern"),  //description to add context in report or other developers
Custom Validation

There will be situation where you have a complex data setup and require you own custom logic to use for data validation. You can achieve this via setting your own SQL expression that returns a boolean value. An example is seen below where we want to check the array update_history, that each entry has updated_time greater than a certain timestamp.

validation().expr("FORALL(update_history, x -> x.updated_time > TIMESTAMP('2022-01-01 00:00:00'))"),

validation.expr("FORALL(update_history, x -> x.updated_time > TIMESTAMP('2022-01-01 00:00:00'))"),

If you want to know what other SQL function are available for you to use, check this page.

Group By Validation

There are scenarios where you want to validate against grouped values or the whole dataset via aggregations. An example would be validating that each customer's transactions sum is greater than 0.

Validation Criteria

Line 1: validation.groupBy().count().isEqual(100)

  • Method Chaining
    • groupBy(): Group by whole dataset.
    • count(): Counts the number of dataset elements.
    • isEqual(100): Checks if the count is equal to 100.
  • Validation Rule
    • This line ensures that the count of the total dataset is exactly 100.

Line 2: validation.groupBy("account_id").max("balance").lessThan(900)

  • Method Chaining
    • groupBy("account_id"): Groups the data based on the account_id field.
    • max("balance"): Calculates the maximum value of the balance field within each group.
    • lessThan(900): Checks if the maximum balance in each group is less than 900.
  • Validation Rule
    • This line ensures that, for each group identified by account_id the maximum balance is less than 900.
Considerations
validation().groupBy().count().isEqual(100),
validation().groupBy("account_id").max("balance").lessThan(900)

validation.groupBy().count().isEqual(100),
validation.groupBy("account_id").max("balance").lessThan(900)

Sample Validation

To try cover the majority of validation cases, the below has been created.

var jsonTask = json("my_json", "/opt/app/data/json")
        .validations(
                validation().col("customer_details.name").matches("[A-Z][a-z]+ [A-Z][a-z]+").errorThreshold(0.1).description("Names generally follow the same pattern"),
                validation().col("date").isNotNull().errorThreshold(10),
                validation().col("balance").greaterThan(500),
                validation().expr("YEAR(date) == year"),
                validation().col("status").in("open", "closed", "pending").errorThreshold(0.2).description("Could be new status introduced"),
                validation().col("customer_details.age").greaterThan(18),
                validation().expr("FORALL(update_history, x -> x.updated_time > TIMESTAMP('2022-01-01 00:00:00'))"),
                validation().col("update_history").greaterThanSize(2),
                validation().unique("account_id"),
                validation().groupBy().count().isEqual(1000),
                validation().groupBy("account_id").max("balance").lessThan(900)
        );

var config = configuration()
        .generatedReportsFolderPath("/opt/app/data/report")
        .enableValidation(true)
        .enableGenerateData(false);

execute(config, jsonTask);

val jsonTask = json("my_json", "/opt/app/data/json")
  .validations(
    validation.col("customer_details.name").matches("[A-Z][a-z]+ [A-Z][a-z]+").errorThreshold(0.1).description("Names generally follow the same pattern"),
    validation.col("date").isNotNull.errorThreshold(10),
    validation.col("balance").greaterThan(500),
    validation.expr("YEAR(date) == year"),
    validation.col("status").in("open", "closed", "pending").errorThreshold(0.2).description("Could be new status introduced"),
    validation.col("customer_details.age").greaterThan(18),
    validation.expr("FORALL(update_history, x -> x.updated_time > TIMESTAMP('2022-01-01 00:00:00'))"),
    validation.col("update_history").greaterThanSize(2),
    validation.unique("account_id"),
    validation.groupBy().count().isEqual(1000),
    validation.groupBy("account_id").max("balance").lessThan(900)
  )

val config = configuration
  .generatedReportsFolderPath("/opt/app/data/report")
  .enableValidation(true)
  .enableGenerateData(false)

execute(config, jsonTask)

Run

Let's try run.

./run.sh
#input class MyValidationJavaPlan or MyValidationPlan
#after completing, check report at docker/sample/report/index.html

It should look something like this.

Check the full example at ValidationPlanRun inside the examples repo.