io.druid.query.extraction

Interface DimExtractionFn

All Known Implementing Classes:

JavascriptDimExtractionFn, MatchingDimExtractionFn, RegexDimExtractionFn, SearchQuerySpecDimExtractionFn, TimeDimExtractionFn

public interface DimExtractionFn

Method Summary

Methods

Modifier and Type	Method and Description
String	apply(String dimValue) The "extraction" function.
byte[]	getCacheKey() Returns a byte[] unique to all concrete implementations of DimExtractionFn.
boolean	preservesOrdering() Offers information on whether the extraction will preserve the original ordering of the values.

Method Detail

getCacheKey

byte[] getCacheKey()

Returns a byte[] unique to all concrete implementations of DimExtractionFn. This byte[] is used to generate a cache key for the specific query.

Returns:

a byte[] unit to all concrete implements of DimExtractionFn

apply

String apply(String dimValue)

The "extraction" function. This should map a dimension value into some other value. In order to maintain the "null and empty string are equivalent" semantics that Druid provides, the empty string is considered invalid output for this method and should instead return null. This is a contract on the method rather than enforced at a lower level in order to eliminate a global check for extraction functions that do not already need one.

Parameters:

dimValue - the original value of the dimension

Returns:

a value that should be used instead of the original

preservesOrdering

boolean preservesOrdering()

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