Package org.apache.lucene.util.packed
Packed integer arrays and streams.
The packed package provides
- sequential and random access capable arrays of positive longs,
- routines for efficient serialization and deserialization of streams of packed integers.
The main access point is the PackedInts factory.
In-memory structures
PackedInts.Mutable- Only supports positive longs.
- Requires the number of bits per value to be known in advance.
- Random-access for both writing and reading.
GrowableWriter- Same as PackedInts.Mutable but grows the number of bits per values when needed.
- Useful to build a PackedInts.Mutable from a read-once stream of longs.
PagedGrowableWriter- Slices data into fixed-size blocks stored in GrowableWriters.
- Supports more than 2B values.
- You should use PackedLongValues instead if you don't need random write access.
PackedLongValues.deltaPackedBuilder(int, float)- Can store any sequence of longs.
- Compression is good when values are close to each other.
- Supports random reads, but only sequential writes.
- Can address up to 2^42 values.
PackedLongValues.packedBuilder(int, float)- Same as deltaPackedBuilder but assumes values are 0-based.
PackedLongValues.monotonicBuilder(int, float)- Same as deltaPackedBuilder except that compression is good when the stream is a succession of affine functions.
Disk-based structures
PackedInts.Writer,PackedInts.Reader,PackedInts.ReaderIterator- Only supports positive longs.
- Requires the number of bits per value to be known in advance.
- Supports both fast sequential access with low memory footprint with ReaderIterator and random-access by either loading values in memory or leaving them on disk with Reader.
BlockPackedWriter,BlockPackedReaderIterator- Splits the stream into fixed-size blocks.
- Compression is good when values are close to each other.
- Can address up to 2B * blockSize values.
MonotonicBlockPackedWriter,MonotonicBlockPackedReader- Same as the non-monotonic variants except that compression is good when the stream is a succession of affine functions.
- The reason why there is no sequential access is that if you need sequential access, you should rather delta-encode and use BlockPackedWriter.
PackedDataOutput,PackedDataInput- Writes sequences of longs where each long can use any number of bits.
-
Interface Summary Interface Description PackedInts.Decoder A decoder for packed integers.PackedInts.Encoder An encoder for packed integers.PackedInts.ReaderIterator Run-once iterator interface, to decode previously saved PackedInts. -
Class Summary Class Description AbstractPagedMutable<T extends AbstractPagedMutable<T>> Base implementation forPagedMutableandPagedGrowableWriter.BlockPackedReaderIterator Reader for sequences of longs written withBlockPackedWriter.BlockPackedWriter A writer for large sequences of longs.DirectMonotonicReader Retrieves an instance previously written byDirectMonotonicWriter.DirectMonotonicReader.Meta In-memory metadata that needs to be kept around forDirectMonotonicReaderto read data from disk.DirectMonotonicWriter Write monotonically-increasing sequences of integers.DirectReader Retrieves an instance previously written byDirectWriterDirectWriter Class for writing packed integers to be directly read from Directory.GrowableWriter ImplementsPackedInts.Mutable, but grows the bit count of the underlying packed ints on-demand.MonotonicBlockPackedReader Provides random access to a stream written withMonotonicBlockPackedWriter.MonotonicBlockPackedWriter A writer for large monotonically increasing sequences of positive longs.PackedDataInput ADataInputwrapper to read unaligned, variable-length packed integers.PackedDataOutput ADataOutputwrapper to write unaligned, variable-length packed integers.PackedInts Simplistic compression for array of unsigned long values.PackedInts.FormatAndBits Simple class that holds a format and a number of bits per value.PackedInts.Mutable A packed integer array that can be modified.PackedInts.NullReader APackedInts.Readerwhich has all its values equal to 0 (bitsPerValue = 0).PackedInts.Reader A read-only random access array of positive integers.PackedInts.Writer A write-once Writer.PackedLongValues Utility class to compress integers into aLongValuesinstance.PackedLongValues.Builder A Builder for aPackedLongValuesinstance.PagedGrowableWriter PagedMutable APagedMutable. -
Enum Summary Enum Description PackedInts.Format A format to write packed ints.