io.druid.query.extraction

Interface ExtractionFn

All Known Implementing Classes:

BucketExtractionFn, CascadeExtractionFn, DimExtractionFn, FunctionalExtraction, IdentityExtractionFn, JavaScriptExtractionFn, LookupExtractionFn, LowerExtractionFn, MatchingDimExtractionFn, RegexDimExtractionFn, RegisteredLookupExtractionFn, SearchQuerySpecDimExtractionFn, StringFormatExtractionFn, StrlenExtractionFn, SubstringDimExtractionFn, TimeDimExtractionFn, TimeFormatExtractionFn, UpperExtractionFn

public interface ExtractionFn

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	ExtractionFn.ExtractionType

Method Summary

Modifier and Type	Method and Description
String	apply(long value) The "extraction" function.
String	apply(Object value) The "extraction" function.
String	apply(String value) The "extraction" function.
byte[]	getCacheKey() Returns a byte[] unique to all concrete implementations of DimExtractionFn.
ExtractionFn.ExtractionType	getExtractionType() A dim extraction can be of one of two types, renaming or rebucketing.
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(Object value)

The "extraction" function. This should map an Object into some String 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:

value - the original value of the dimension

Returns:

a value that should be used instead of the original

apply

String apply(String value)

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

Like 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

apply

String apply(long value)

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

Like 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

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

getExtractionType

ExtractionFn.ExtractionType getExtractionType()

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