org.apache.druid.query.extraction

Class FunctionalExtraction

java.lang.Object

org.apache.druid.query.extraction.DimExtractionFn

org.apache.druid.query.extraction.FunctionalExtraction

All Implemented Interfaces:

Cacheable, ExtractionFn

Direct Known Subclasses:

LookupExtractionFn

public abstract class FunctionalExtraction
extends DimExtractionFn

Functional extraction uses a function to find the new value. null values in the range can either retain the domain's value, or replace the null value with "replaceMissingValueWith"

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.druid.query.extraction.ExtractionFn

ExtractionFn.ExtractionType

Constructor Summary

Constructors

Constructor and Description
FunctionalExtraction(com.google.common.base.Function<String,String> extractionFunction, boolean retainMissingValue, String replaceMissingValueWith, boolean injective) The general constructor which handles most of the logic for extractions which can be expressed as a function of string-->string

Method Summary

Modifier and Type	Method and Description
String	apply(String value) The "extraction" function.
ExtractionFn.ExtractionType	getExtractionType() A dim extraction can be of one of two types, renaming or rebucketing.
String	getReplaceMissingValueWith()
boolean	isInjective()
boolean	isRetainMissingValue()
boolean	preservesOrdering() Offers information on whether the extraction will preserve the original ordering of the values.

Methods inherited from class org.apache.druid.query.extraction.DimExtractionFn

apply, apply

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.druid.java.util.common.Cacheable

getCacheKey

Constructor Detail

FunctionalExtraction

public FunctionalExtraction(com.google.common.base.Function<String,String> extractionFunction,
                            boolean retainMissingValue,
                            String replaceMissingValueWith,
                            boolean injective)

The general constructor which handles most of the logic for extractions which can be expressed as a function of string-->string

Parameters:

extractionFunction - The function to call when doing the extraction. The function must be able to accept a null input.

retainMissingValue - Boolean value on if functions which result in `null` should use the original value or should be kept as `null`

replaceMissingValueWith - String value to replace missing values with (instead of `null`)

injective - If this function always has 1:1 renames and the domain has the same cardinality of the input, this should be true and enables optimized query paths.

Method Detail

isRetainMissingValue

public boolean isRetainMissingValue()

getReplaceMissingValueWith

public String getReplaceMissingValueWith()

isInjective

public boolean isInjective()

apply

@Nullable
public String apply(@Nullable
                              String value)

Description copied from interface: ExtractionFn

The "extraction" function. This should map a String value into some other String value.

Like ExtractionFn.apply(Object), the empty string is considered invalid output for this method and it should instead return null.

Parameters:

value - the original value of the dimension

Returns:

a value that should be used instead of the original

preservesOrdering

public boolean preservesOrdering()

Description copied from interface: ExtractionFn

Offers information on whether the extraction will preserve the original ordering of the values.

Some optimizations of queries is possible if ordering is preserved. Null values *do* count towards ordering.

Returns:

true if ordering is preserved, false otherwise

getExtractionType

public ExtractionFn.ExtractionType getExtractionType()

Description copied from interface: ExtractionFn

A dim extraction can be of one of two types, renaming or rebucketing. In the `ONE_TO_ONE` case, a unique values is modified into another unique value. In the `MANY_TO_ONE` case, there is no longer a 1:1 relation between old dimension value and new dimension value

Returns:

ExtractionFn.ExtractionType declaring what kind of manipulation this function does