Module org.apache.lucene.core
Package org.apache.lucene.codecs

Class MultiLevelSkipListReader

java.lang.Object
org.apache.lucene.codecs.MultiLevelSkipListReader
All Implemented Interfaces:
Closeable, AutoCloseable
Direct Known Subclasses:
Lucene50SkipReader, Lucene84SkipReader, Lucene90SkipReader, Lucene99SkipReader, SimpleTextSkipReader
public abstract class MultiLevelSkipListReader extends Object implements Closeable
This abstract class reads skip lists with multiple levels.

See MultiLevelSkipListWriter for the information about the encoding of the multi level skip lists.

Subclasses must implement the abstract method readSkipData(int, IndexInput) which defines the actual format of the skip data.

  • Field Details

    • maxNumberOfSkipLevels

      protected int maxNumberOfSkipLevels
      the maximum number of skip levels possible for this index

    • numberOfSkipLevels

      protected int numberOfSkipLevels
      number of levels in this skip list

    • docCount

      private int docCount

    • skipStream

      private IndexInput[] skipStream
      skipStream for each level.

    • skipPointer

      private long[] skipPointer
      The start pointer of each skip level.

    • skipInterval

      private int[] skipInterval
      skipInterval of each level.

    • numSkipped

      private int[] numSkipped
      Number of docs skipped per level. It's possible for some values to overflow a signed int, but this has been accounted for.

    • skipDoc

      protected int[] skipDoc
      Doc id of current skip entry per level.

    • lastDoc

      private int lastDoc
      Doc id of last read skip entry with docId <= target.

    • childPointer

      private long[] childPointer
      Child pointer of current skip entry per level.

    • lastChildPointer

      private long lastChildPointer
      childPointer of last read skip entry with docId <= target.

    • skipMultiplier

      private final int skipMultiplier

  • Constructor Details

    • MultiLevelSkipListReader

      protected MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval, int skipMultiplier)
      Creates a MultiLevelSkipListReader.

    • MultiLevelSkipListReader

      protected MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval)
      Creates a MultiLevelSkipListReader, where skipInterval and skipMultiplier are the same.

  • Method Details

    • getDoc

      public int getDoc()
      Returns the id of the doc to which the last call of skipTo(int) has skipped.

    • skipTo

      public int skipTo(int target) throws IOException
      Skips entries to the first beyond the current whose document number is greater than or equal to target. Returns the current doc count.
      Throws:
      IOException

    • loadNextSkip

      private boolean loadNextSkip(int level) throws IOException
      Throws:
      IOException

    • seekChild

      protected void seekChild(int level) throws IOException
      Seeks the skip entry on the given level
      Throws:
      IOException

    • close

      public void close() throws IOException
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException

    • init

      public void init(long skipPointer, int df) throws IOException
      Initializes the reader, for reuse on a new term.
      Throws:
      IOException

    • loadSkipLevels

      private void loadSkipLevels() throws IOException
      Loads the skip levels
      Throws:
      IOException

    • readSkipData

      protected abstract int readSkipData(int level, IndexInput skipStream) throws IOException
      Subclasses must implement the actual skip data encoding in this method.
      Parameters:
      level - the level skip data shall be read from
      skipStream - the skip stream to read from
      Throws:
      IOException

    • readLevelLength

      protected long readLevelLength(IndexInput skipStream) throws IOException
      read the length of the current level written via MultiLevelSkipListWriter.writeLevelLength(long, IndexOutput).
      Parameters:
      skipStream - the IndexInput the length shall be read from
      Returns:
      level length
      Throws:
      IOException

    • readChildPointer

      protected long readChildPointer(IndexInput skipStream) throws IOException
      read the child pointer written via MultiLevelSkipListWriter.writeChildPointer(long, DataOutput).
      Parameters:
      skipStream - the IndexInput the child pointer shall be read from
      Returns:
      child pointer
      Throws:
      IOException

    • setLastSkipData

      protected void setLastSkipData(int level)
      Copies the values of the last read skip entry on this level