Class Lucene99SkipReader
- java.lang.Object
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- org.apache.lucene.codecs.MultiLevelSkipListReader
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- org.apache.lucene.backward_codecs.lucene99.Lucene99SkipReader
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- All Implemented Interfaces:
Closeable,AutoCloseable
public class Lucene99SkipReader 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 Lucene99SkipWriter)In this case, MultiLevelSkipListReader will use the last document as a skip point, while Lucene99SkipReader should assume no skip point will comes.
If we use the interface directly in Lucene99SkipReader, 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)
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Field Summary
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Fields inherited from class org.apache.lucene.codecs.MultiLevelSkipListReader
maxNumberOfSkipLevels, numberOfSkipLevels, skipDoc
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Constructor Summary
Constructors Constructor Description Lucene99SkipReader(IndexInput skipStream, int maxSkipLevels, boolean hasPos, boolean hasOffsets, boolean hasPayloads)Sole constructor.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description longgetDocPointer()Returns the doc pointer of the doc to which the last call ofMultiLevelSkipListReader.skipTo(int)has skipped.intgetNextSkipDoc()Return the next skip doc, no skipping can be performed until this doc.intgetPayloadByteUpto()Return the number of bytes in the pay block that belongs to docs from the previous block.longgetPayPointer()Returns the pointer in the pay file.intgetPosBufferUpto()Return the start offset in the position block.longgetPosPointer()Returns the pointer in the pos file.voidinit(long skipPointer, long docBasePointer, long posBasePointer, long payBasePointer, int df)Initialize state.protected voidreadImpacts(int level, IndexInput skipStream)Read impacts.protected intreadSkipData(int level, IndexInput skipStream)protected voidseekChild(int level)protected voidsetLastSkipData(int level)protected inttrim(int df)Trim original docFreq to tell skipReader read proper number of skip points.-
Methods inherited from class org.apache.lucene.codecs.MultiLevelSkipListReader
close, getDoc, init, readChildPointer, readLevelLength, skipTo
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Constructor Detail
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Lucene99SkipReader
public Lucene99SkipReader(IndexInput skipStream, int maxSkipLevels, boolean hasPos, boolean hasOffsets, boolean hasPayloads)
Sole constructor.
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Method Detail
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trim
protected int trim(int df)
Trim original docFreq to tell skipReader read proper number of skip points.Since our definition in Lucene99Skip* 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
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init
public void init(long skipPointer, long docBasePointer, long posBasePointer, long payBasePointer, int df) throws IOExceptionInitialize state.- Throws:
IOException
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getDocPointer
public long getDocPointer()
Returns the doc pointer of the doc to which the last call ofMultiLevelSkipListReader.skipTo(int)has skipped.
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getPosPointer
public long getPosPointer()
Returns the pointer in the pos file.
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getPosBufferUpto
public int getPosBufferUpto()
Return the start offset in the position block.
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getPayPointer
public long getPayPointer()
Returns the pointer in the pay file.
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getPayloadByteUpto
public int getPayloadByteUpto()
Return the number of bytes in the pay block that belongs to docs from the previous block.
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getNextSkipDoc
public int getNextSkipDoc()
Return the next skip doc, no skipping can be performed until this doc.
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seekChild
protected void seekChild(int level) throws IOException- Overrides:
seekChildin classMultiLevelSkipListReader- Throws:
IOException
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setLastSkipData
protected void setLastSkipData(int level)
- Overrides:
setLastSkipDatain classMultiLevelSkipListReader
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readSkipData
protected int readSkipData(int level, IndexInput skipStream) throws IOException- Specified by:
readSkipDatain classMultiLevelSkipListReader- Throws:
IOException
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readImpacts
protected void readImpacts(int level, IndexInput skipStream) throws IOExceptionRead impacts. The default implementation skips them.- Throws:
IOException
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