org.apache.lucene.codecs.lucene54

Class Lucene54DocValuesFormat

java.lang.Object

org.apache.lucene.codecs.DocValuesFormat

org.apache.lucene.codecs.lucene54.Lucene54DocValuesFormat

All Implemented Interfaces:

NamedSPILoader.NamedSPI

public final class Lucene54DocValuesFormat
extends DocValuesFormat

Lucene 5.4 DocValues format.

Encodes the five per-document value types (Numeric,Binary,Sorted,SortedSet,SortedNumeric) with these strategies:

NUMERIC:

• Delta-compressed: per-document integers written as deltas from the minimum value, compressed with bitpacking. For more information, see DirectWriter.
• Table-compressed: when the number of unique values is very small (< 256), and when there are unused "gaps" in the range of values used (such as SmallFloat), a lookup table is written instead. Each per-document entry is instead the ordinal to this table, and those ordinals are compressed with bitpacking (DirectWriter).
• GCD-compressed: when all numbers share a common divisor, such as dates, the greatest common denominator (GCD) is computed, and quotients are stored using Delta-compressed Numerics.
• Monotonic-compressed: when all numbers are monotonically increasing offsets, they are written as blocks of bitpacked integers, encoding the deviation from the expected delta.
• Const-compressed: when there is only one possible non-missing value, only the missing bitset is encoded.
• Sparse-compressed: only documents with a value are stored, and lookups are performed using binary search.

BINARY:

• Fixed-width Binary: one large concatenated byte[] is written, along with the fixed length. Each document's value can be addressed directly with multiplication (docID * length).
• Variable-width Binary: one large concatenated byte[] is written, along with end addresses for each document. The addresses are written as Monotonic-compressed numerics.
• Prefix-compressed Binary: values are written in chunks of 16, with the first value written completely and other values sharing prefixes. chunk addresses are written as Monotonic-compressed numerics. A reverse lookup index is written from a portion of every 1024th term.

SORTED:

• Sorted: a mapping of ordinals to deduplicated terms is written as Binary, along with the per-document ordinals written using one of the numeric strategies above.

SORTED_SET:

• Single: if all documents have 0 or 1 value, then data are written like SORTED.
• SortedSet table: when there are few unique sets of values (< 256) then each set is assigned an id, a lookup table is written and the mapping from document to set id is written using the numeric strategies above.
• SortedSet: a mapping of ordinals to deduplicated terms is written as Binary, an ordinal list and per-document index into this list are written using the numeric strategies above.

SORTED_NUMERIC:

• Single: if all documents have 0 or 1 value, then data are written like NUMERIC.
• SortedSet table: when there are few unique sets of values (< 256) then each set is assigned an id, a lookup table is written and the mapping from document to set id is written using the numeric strategies above.
• SortedNumeric: a value list and per-document index into this list are written using the numeric strategies above.

Files:

1. .dvd: DocValues data
2. .dvm: DocValues metadata

WARNING: This API is experimental and might change in incompatible ways in the next release.

Constructor Summary

Constructors

Constructor and Description
Lucene54DocValuesFormat() Sole Constructor

Method Summary

Modifier and Type	Method and Description
DocValuesConsumer	fieldsConsumer(SegmentWriteState state) Returns a DocValuesConsumer to write docvalues to the index.
DocValuesProducer	fieldsProducer(SegmentReadState state) Returns a DocValuesProducer to read docvalues from the index.

Methods inherited from class org.apache.lucene.codecs.DocValuesFormat

availableDocValuesFormats, forName, getName, reloadDocValuesFormats, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

Lucene54DocValuesFormat

public Lucene54DocValuesFormat()

Sole Constructor

Method Detail

fieldsConsumer

public DocValuesConsumer fieldsConsumer(SegmentWriteState state)
                                 throws IOException

Description copied from class: DocValuesFormat

Returns a DocValuesConsumer to write docvalues to the index.

Specified by:

fieldsConsumer in class DocValuesFormat

Throws:

IOException

fieldsProducer

public DocValuesProducer fieldsProducer(SegmentReadState state)
                                 throws IOException

Description copied from class: DocValuesFormat

Returns a DocValuesProducer to read docvalues from the index.

NOTE: by the time this call returns, it must hold open any files it will need to use; else, those files may be deleted. Additionally, required files may be deleted during the execution of this call before there is a chance to open them. Under these circumstances an IOException should be thrown by the implementation. IOExceptions are expected and will automatically cause a retry of the segment opening logic with the newly revised segments.

Specified by:

fieldsProducer in class DocValuesFormat

Throws:

IOException