ConstraintEvaluator (AWS Athena Query Federation 2022.47.1 API)

java.lang.Object
- com.amazonaws.athena.connector.lambda.domain.predicate.ConstraintEvaluator

All Implemented Interfaces:

AutoCloseable
```
public class ConstraintEvaluator
extends Object
implements AutoCloseable
```
Used to apply predicates to values inside your connector. Ideally you would also be able to push constraints into your source system (e.g. RDBMS via SQL). For each value you'd like to write for a given row, you call the 'apply' function on this class and if the values for all columns in the row return 'true' that indicates that the row passes the constraints.
After being used, ConstraintEvaluator instance must be closed to ensure no Apache Arrow resources used by Markers that it creates as part of evaluation are leaked.

See Also:

for details on how Constraints are represented and individually applied.

Constructor Summary

Constructors
Constructor	Description
`ConstraintEvaluator(BlockAllocator allocator, org.apache.arrow.vector.types.pojo.Schema schema, Constraints constraints)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`apply(String fieldName, Object value)`	Used check if the provided value passes all constraints on the given field.
`void`	`close()`	Frees any Apache Arrow resources held by this Constraint Evaluator.
`static ConstraintEvaluator`	`emptyEvaluator()`	This convenience method builds an empty Evaluator that can be useful when no constraints are present.
`Optional<ConstraintProjector>`	`makeConstraintProjector(String fieldName)`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - ConstraintEvaluator
```
public ConstraintEvaluator(BlockAllocator allocator,
                           org.apache.arrow.vector.types.pojo.Schema schema,
                           Constraints constraints)
```
- Method Detail
  - emptyEvaluator
```
public static ConstraintEvaluator emptyEvaluator()
```
    This convenience method builds an empty Evaluator that can be useful when no constraints are present.
    
    Returns:
    
    An empty ConstraintEvaluator which always returns true when applied to a value for any field.
  - apply
```
public boolean apply(String fieldName,
                     Object value)
```
    Used check if the provided value passes all constraints on the given field.
    
    Parameters:
    
    fieldName - The name of the field whoe's constraints we'd like to apply to the value.
    
    value - The value to test.
    
    Returns:
    
    True if the value passed all constraints for the given field, False otherwise. This method also returns True if the field has no constraints, including if the field is unknown.
  - makeConstraintProjector
```
public Optional<ConstraintProjector> makeConstraintProjector(String fieldName)
```
  - close
```
public void close()
           throws Exception
```
    Frees any Apache Arrow resources held by this Constraint Evaluator.
    
    Specified by:
    
    close in interface AutoCloseable
    
    Throws:
    
    Exception