Class Lucene99SkipReader
- All Implemented Interfaces:
Closeable
,AutoCloseable
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
Fields inherited from class org.apache.lucene.codecs.MultiLevelSkipListReader
maxNumberOfSkipLevels, numberOfSkipLevels, skipDoc
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Constructor Summary
ConstructorDescriptionLucene99SkipReader
(IndexInput skipStream, int maxSkipLevels, boolean hasPos, boolean hasOffsets, boolean hasPayloads) -
Method Summary
Modifier and TypeMethodDescriptionlong
Returns the doc pointer of the doc to which the last call ofMultiLevelSkipListReader.skipTo(int)
has skipped.int
int
long
int
long
void
init
(long skipPointer, long docBasePointer, long posBasePointer, long payBasePointer, int df) protected void
readImpacts
(int level, IndexInput skipStream) protected int
readSkipData
(int level, IndexInput skipStream) Subclasses must implement the actual skip data encoding in this method.protected void
seekChild
(int level) Seeks the skip entry on the given levelprotected void
setLastSkipData
(int level) Copies the values of the last read skip entry on this levelprotected int
trim
(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 Details
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Lucene99SkipReader
public Lucene99SkipReader(IndexInput skipStream, int maxSkipLevels, boolean hasPos, boolean hasOffsets, boolean hasPayloads)
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Method Details
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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 IOException - 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. -
getPosPointer
public long getPosPointer() -
getPosBufferUpto
public int getPosBufferUpto() -
getPayPointer
public long getPayPointer() -
getPayloadByteUpto
public int getPayloadByteUpto() -
getNextSkipDoc
public int getNextSkipDoc() -
seekChild
Description copied from class:MultiLevelSkipListReader
Seeks the skip entry on the given level- Overrides:
seekChild
in classMultiLevelSkipListReader
- Throws:
IOException
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setLastSkipData
protected void setLastSkipData(int level) Description copied from class:MultiLevelSkipListReader
Copies the values of the last read skip entry on this level- Overrides:
setLastSkipData
in classMultiLevelSkipListReader
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readSkipData
Description copied from class:MultiLevelSkipListReader
Subclasses must implement the actual skip data encoding in this method.- Specified by:
readSkipData
in classMultiLevelSkipListReader
- Parameters:
level
- the level skip data shall be read fromskipStream
- the skip stream to read from- Throws:
IOException
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readImpacts
- Throws:
IOException
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