Package org.apache.lucene.codecs.lucene50

Class Lucene50SkipReader

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    Direct Known Subclasses:
    Lucene50ScoreSkipReader
    class Lucene50SkipReader
extends MultiLevelSkipListReader
    Implements the skip list reader for block postings format that stores positions and payloads. Although this skipper uses MultiLevelSkipListReader as an interface, its definition of skip position will be a little different. For example, when skipInterval = blockSize = 3, df = 2*skipInterval = 6, 0 1 2 3 4 5 d d d d d d (posting list) ^ ^ (skip point in MultiLeveSkipWriter) ^ (skip point in Lucene50SkipWriter) In this case, MultiLevelSkipListReader will use the last document as a skip point, while Lucene50SkipReader should assume no skip point will comes. If we use the interface directly in Lucene50SkipReader, it may silly try to read another skip data after the only skip point is loaded. To illustrate this, we can call skipTo(d[5]), since skip point d[3] has smaller docId, and numSkipped+blockSize== df, the MultiLevelSkipListReader will assume the skip list isn't exhausted yet, and try to load a non-existed skip point Therefore, we'll trim df before passing it to the interface. see trim(int)

    • Field Detail

      • version

        private final int version

      • docPointer

        private long[] docPointer

      • posPointer

        private long[] posPointer

      • payPointer

        private long[] payPointer

      • posBufferUpto

        private int[] posBufferUpto

      • payloadByteUpto

        private int[] payloadByteUpto

      • lastPosPointer

        private long lastPosPointer

      • lastPayPointer

        private long lastPayPointer

      • lastPayloadByteUpto

        private int lastPayloadByteUpto

      • lastDocPointer

        private long lastDocPointer

      • lastPosBufferUpto

        private int lastPosBufferUpto

    • Constructor Detail

      • Lucene50SkipReader

        public Lucene50SkipReader​(int version,
                          IndexInput skipStream,
                          int maxSkipLevels,
                          boolean hasPos,
                          boolean hasOffsets,
                          boolean hasPayloads)

    • Method Detail

      • trim

        protected int trim​(int df)
        Trim original docFreq to tell skipReader read proper number of skip points. Since our definition in Lucene50Skip* is a little different from MultiLevelSkip* This trimmed docFreq will prevent skipReader from: 1. silly reading a non-existed skip point after the last block boundary 2. moving into the vInt block

      • init

        public void init​(long skipPointer,
                 long docBasePointer,
                 long posBasePointer,
                 long payBasePointer,
                 int df)
          throws java.io.IOException
        Throws:
        java.io.IOException

      • getPosPointer

        public long getPosPointer()

      • getPosBufferUpto

        public int getPosBufferUpto()

      • getPayPointer

        public long getPayPointer()

      • getPayloadByteUpto

        public int getPayloadByteUpto()

      • getNextSkipDoc

        public int getNextSkipDoc()

      • readSkipData

        protected int readSkipData​(int level,
                           IndexInput skipStream)
                    throws java.io.IOException
        Description copied from class: MultiLevelSkipListReader
        Subclasses must implement the actual skip data encoding in this method.
        Specified by:
        readSkipData in class MultiLevelSkipListReader
        Parameters:
        level - the level skip data shall be read from
        skipStream - the skip stream to read from
        Throws:
        java.io.IOException

      • readImpacts

        protected void readImpacts​(int level,
                           IndexInput skipStream)
                    throws java.io.IOException
        Throws:
        java.io.IOException