Introduction
Constraints
Data constraints allow you to apply business rules and data integrity checks to ensure data quality during processing. When a constraint is violated, a ConstraintViolationException is thrown with details about the violating row.
Unique Constraints
Ensure that values in specified columns are unique across the entire dataset.
<?php
use function Flow\ETL\DSL\{data_frame, from_array, constraint_unique, to_output};
$dataFrame = data_frame()
->read(from_array([
['email' => '[email protected]', 'username' => 'user1'],
['email' => '[email protected]', 'username' => 'user2'],
['email' => '[email protected]', 'username' => 'user3'], // This will cause constraint violation
]))
->constrain(constraint_unique('email'))
->write(to_output())
->run();
Multiple Column Constraints
Ensure unique combinations across multiple columns:
<?php
use function Flow\ETL\DSL\{constraint_unique};
$dataFrame = data_frame()
->read($extractor)
->constrain(constraint_unique('username', 'tenant_id'))
->write($loader)
->run();
Custom Constraints
You can implement custom constraints by creating classes that implement the Constraint interface:
<?php
use Flow\ETL\{Constraint, Row};
class AgeRangeConstraint implements Constraint
{
public function __construct(private int $minAge, private int $maxAge) {}
public function isSatisfiedBy(Row $row): bool
{
$age = $row->get('age')->value();
return $age >= $this->minAge && $age <= $this->maxAge;
}
public function toString(): string
{
return "Age must be between {$this->minAge} and {$this->maxAge}";
}
public function violation(Row $row): string
{
return "Age {$row->get('age')->value()} is outside allowed range";
}
}
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