Package org.apache.lucene.index

Interface IndexSorter

All Known Implementing Classes:

IndexSorter.BinarySorter, IndexSorter.DoubleSorter, IndexSorter.FloatSorter, IndexSorter.IntSorter, IndexSorter.LongSorter, IndexSorter.StringSorter

public interface IndexSorter

Handles how documents should be sorted in an index, both within a segment and between segments.

Implementers must provide the following methods:

• getDocComparator(LeafReader,int) - an object that determines how documents within a segment are to be sorted
• getComparableValues(List) - an object that reads and compares the sort value of documents across segments, used for merge sorting. The default implementation adapts getComparableProviders(List), so sorts whose value can be expressed as a long only need to implement the latter.
• getProviderName() - the SPI-registered name of a SortFieldProvider to serialize the sort

The companion SortFieldProvider should be registered with SPI via META-INF/services

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	IndexSorter.BinaryDocValuesProvider	Provide a BinaryDocValues instance for a LeafReader
static final class	IndexSorter.BinarySorter	Sorts documents by the bytes of a BinaryDocValues instance, using the given comparator.
static interface	IndexSorter.ComparableProvider	Used for sorting documents across segments
static interface	IndexSorter.ComparableValues	Caches the sort value of the current document of every segment being merged, and compares them.
static interface	IndexSorter.DocComparator	A comparator of doc IDs, used for sorting documents within a segment
static final class	IndexSorter.DoubleSorter	Sorts documents based on double values from a NumericDocValues instance
static final class	IndexSorter.FloatSorter	Sorts documents based on float values from a NumericDocValues instance
static final class	IndexSorter.IntSorter	Sorts documents based on integer values from a NumericDocValues instance
static final class	IndexSorter.LongSorter	Sorts documents based on long values from a NumericDocValues instance
static interface	IndexSorter.NumericDocValuesProvider	Provide a NumericDocValues instance for a LeafReader
static interface	IndexSorter.SortedDocValuesProvider	Provide a SortedDocValues instance for a LeafReader
static final class	IndexSorter.StringSorter	Sorts documents based on terms from a SortedDocValues instance

Method Summary

Modifier and Type	Method	Description
default IndexSorter.ComparableProvider[]	getComparableProviders(List<? extends LeafReader> readers)	Get an array of IndexSorter.ComparableProvider, one per segment, for merge sorting documents in different segments.
default IndexSorter.ComparableValues	getComparableValues(List<? extends LeafReader> readers)	Get a IndexSorter.ComparableValues, used for merge sorting documents across the given segments.
IndexSorter.DocComparator	getDocComparator(LeafReader reader, int maxDoc)	Get a comparator that determines the sort order of docs within a single Reader.
String	getProviderName()	The SPI-registered name of a SortFieldProvider that will deserialize the parent SortField

Method Details

getComparableProviders

default IndexSorter.ComparableProvider[] getComparableProviders(List<? extends LeafReader> readers)
                                                         throws IOException

Get an array of IndexSorter.ComparableProvider, one per segment, for merge sorting documents in different segments.

Implementations whose sort value is a long should implement this method; it is exposed to the merger through the default getComparableValues(List). Implementations that override getComparableValues(List) directly need not implement this method.

Parameters:

readers - the readers to be merged

Throws:

IOException

getComparableValues

default IndexSorter.ComparableValues getComparableValues(List<? extends LeafReader> readers)
                                                  throws IOException

Get a IndexSorter.ComparableValues, used for merge sorting documents across the given segments.

The default implementation adapts getComparableProviders(List) and is appropriate for any sort whose value can be represented as a long.

Parameters:

readers - the readers to be merged

Throws:

IOException

getDocComparator

IndexSorter.DocComparator getDocComparator(LeafReader reader,
 int maxDoc)
                                    throws IOException

Get a comparator that determines the sort order of docs within a single Reader.

NB We cannot simply use the FieldComparator API because it requires docIDs to be sent in-order. The default implementations allocate array[maxDoc] to hold native values for comparison, but 1) they are transient (only alive while sorting this one segment) and 2) in the typical index sorting case, they are only used to sort newly flushed segments, which will be smaller than merged segments

Parameters:

reader - the Reader to sort

maxDoc - the number of documents in the Reader

Throws:

IOException

getProviderName

String getProviderName()

The SPI-registered name of a SortFieldProvider that will deserialize the parent SortField