org.apache.lucene.codecs.uniformsplit

## Class IntersectBlockReader

- java.lang.Object
- - org.apache.lucene.index.TermsEnum
  - - org.apache.lucene.index.BaseTermsEnum
    - - org.apache.lucene.codecs.uniformsplit.BlockReader
      - - org.apache.lucene.codecs.uniformsplit.IntersectBlockReader

- All Implemented Interfaces:
    Accountable, BytesRefIterator
  Direct Known Subclasses:
    STIntersectBlockReader

      public class IntersectBlockReader
      extends BlockReader

  The "intersect" `TermsEnum` response to `UniformSplitTerms.intersect(CompiledAutomaton, BytesRef)`, intersecting the terms with an automaton.

  By design of the UniformSplit block keys, it is less efficient than `org.apache.lucene.codecs.blocktree.IntersectTermsEnum` for `FuzzyQuery` (-37%). It is slightly slower for `WildcardQuery` (-5%) and slightly faster for `PrefixQuery` (+5%).

  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `protected class` | `IntersectBlockReader.AutomatonNextTermCalculator` This is mostly a copy of AutomatonTermsEnum.
    `protected static class` | `IntersectBlockReader.BlockIteration` Block iteration order.

    - ### Nested classes/interfaces inherited from class org.apache.lucene.index.TermsEnum

      `TermsEnum.SeekStatus`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Automaton` | `automaton`
    `protected IntersectBlockReader.BlockIteration` | `blockIteration` Block iteration order determined when scanning the terms in the current block.
    `protected BytesRef` | `commonSuffix`
    `protected boolean` | `finite`
    `protected int` | `minTermLength`
    `protected IntersectBlockReader.AutomatonNextTermCalculator` | `nextStringCalculator`
    `protected int` | `NUM_CONSECUTIVELY_REJECTED_TERMS_THRESHOLD` Threshold that controls when to attempt to jump to a block away.
    `protected int` | `numConsecutivelyRejectedTerms` Counter of the number of consecutively rejected terms.
    `protected int` | `numMatchedBytes` Number of bytes accepted by the automaton when validating the current term.
    `protected ByteRunAutomaton` | `runAutomaton`
    `protected BytesRef` | `seekTerm` Set this when our current mode is seeking to this term.
    `protected int[]` | `states` Automaton states reached when validating the current term, from 0 to `numMatchedBytes` - 1.

    - ### Fields inherited from class org.apache.lucene.codecs.uniformsplit.BlockReader

      `blockDecoder, blockFirstLineStart, blockHeader, blockHeaderReader, blockInput, blockLine, blockLineReader, blockReadBuffer, blockStartFP, dictionaryBrowser, dictionaryBrowserSupplier, fieldMetadata, forcedTerm, lineIndexInBlock, postingsReader, scratchBlockBytes, scratchBlockLine, scratchTermState, termState, termStateForced, termStateSerializer, termStatesReadBuffer`

    - ### Fields inherited from class org.apache.lucene.index.TermsEnum

      `EMPTY`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `IntersectBlockReader(CompiledAutomaton compiled, BytesRef startTerm, IndexDictionary.BrowserSupplier dictionaryBrowserSupplier, IndexInput blockInput, PostingsReaderBase postingsReader, FieldMetadata fieldMetadata, BlockDecoder blockDecoder)`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected boolean` | `endsWithCommonSuffix(byte[] termBytes, int termLength)` Indicates whether the given term ends with the automaton common suffix.
    `protected int` | `getMinTermLength()` Computes the minimal length of the terms accepted by the automaton.
    `BytesRef` | `next()`
    `protected boolean` | `nextBlock()` Opens the next block.
    `protected BytesRef` | `nextTermInBlockMatching()` Finds the next block line that matches (accepted by the automaton), or null when at end of block.
    `TermsEnum.SeekStatus` | `seekCeil(BytesRef text)`
    `boolean` | `seekExact(BytesRef text)`
    `void` | `seekExact(BytesRef term, TermState state)` Positions this `BlockReader` without re-seeking the term dictionary.
    `void` | `seekExact(long ord)` Not supported.
    `protected boolean` | `seekFirstBlock()`

    - ### Methods inherited from class org.apache.lucene.codecs.uniformsplit.BlockReader

      `clearTermState, compareToMiddleAndJump, createBlockHeaderSerializer, createBlockLineSerializer, createDeltaBaseTermStateSerializer, decodeBlockBytesIfNeeded, docFreq, getOrCreateDictionaryBrowser, impacts, initializeBlockReadLazily, initializeHeader, isBeyondLastTerm, isCurrentTerm, newCorruptIndexException, nextTerm, ord, postings, ramBytesUsed, readHeader, readLineInBlock, readTermState, readTermStateIfNotRead, seekInBlock, seekInBlock, term, termState, totalTermFreq`

    - ### Methods inherited from class org.apache.lucene.index.BaseTermsEnum

      `attributes`

    - ### Methods inherited from class org.apache.lucene.index.TermsEnum

      `postings`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

    - ### Methods inherited from interface org.apache.lucene.util.Accountable

      `getChildResources`

- - ### Field Detail

    - #### NUM_CONSECUTIVELY_REJECTED_TERMS_THRESHOLD

          protected final int NUM_CONSECUTIVELY_REJECTED_TERMS_THRESHOLD

      Threshold that controls when to attempt to jump to a block away.

      This counter is 0 when entering a block. It is incremented each time a term is rejected by the automaton. When the counter is greater than or equal to this threshold, then we compute the next term accepted by the automaton, with `IntersectBlockReader.AutomatonNextTermCalculator`, and we jump to a block away if the next term accepted is greater than the immediate next term in the block.

      A low value, for example 1, improves the performance of automatons requiring many jumps, for example `FuzzyQuery` and most `WildcardQuery`. A higher value improves the performance of automatons with less or no jump, for example `PrefixQuery`. A threshold of 4 seems to be a good balance.

      See Also:
        Constant Field Values

    - #### automaton

          protected final Automaton automaton

    - #### runAutomaton

          protected final ByteRunAutomaton runAutomaton

    - #### finite

          protected final boolean finite

    - #### commonSuffix

          protected final BytesRef commonSuffix

    - #### minTermLength

          protected final int minTermLength

    - #### nextStringCalculator

          protected final IntersectBlockReader.AutomatonNextTermCalculator nextStringCalculator

    - #### seekTerm

          protected BytesRef seekTerm

      Set this when our current mode is seeking to this term. Set to null after.

    - #### numMatchedBytes

          protected int numMatchedBytes

      Number of bytes accepted by the automaton when validating the current term.

    - #### states

          protected int[] states

      Automaton states reached when validating the current term, from 0 to `numMatchedBytes` - 1.

    - #### blockIteration

          protected IntersectBlockReader.BlockIteration blockIteration

      Block iteration order determined when scanning the terms in the current block.

    - #### numConsecutivelyRejectedTerms

          protected int numConsecutivelyRejectedTerms

      Counter of the number of consecutively rejected terms. Depending on `NUM_CONSECUTIVELY_REJECTED_TERMS_THRESHOLD`, this may trigger a jump to a block away.

  - ### Constructor Detail

    - #### IntersectBlockReader

          protected IntersectBlockReader(CompiledAutomaton compiled,
                                         BytesRef startTerm,
                                         IndexDictionary.BrowserSupplier dictionaryBrowserSupplier,
                                         IndexInput blockInput,
                                         PostingsReaderBase postingsReader,
                                         FieldMetadata fieldMetadata,
                                         BlockDecoder blockDecoder)
                                  throws IOException

      Throws:
        `IOException`

  - ### Method Detail

    - #### getMinTermLength

          protected int getMinTermLength()

      Computes the minimal length of the terms accepted by the automaton. This speeds up the term scanning for automatons accepting a finite language.

    - #### next

          public BytesRef next()
                        throws IOException

      Specified by:
        `next` in interface `BytesRefIterator`
      Overrides:
        `next` in class `BlockReader`
      Throws:
        `IOException`

    - #### seekFirstBlock

          protected boolean seekFirstBlock()
                                    throws IOException

      Throws:
        `IOException`

    - #### nextTermInBlockMatching

          protected BytesRef nextTermInBlockMatching()
                                              throws IOException

      Finds the next block line that matches (accepted by the automaton), or null when at end of block.
      Returns:
        The next term in the current block that is accepted by the automaton; or null if none.
      Throws:
        `IOException`

    - #### endsWithCommonSuffix

          protected boolean endsWithCommonSuffix(byte[] termBytes,
                                                 int termLength)

      Indicates whether the given term ends with the automaton common suffix. This allows to quickly skip terms that the automaton would reject eventually.

    - #### nextBlock

          protected boolean nextBlock()
                               throws IOException

      Opens the next block. Depending on the `blockIteration` order, it may be the very next block, or a block away that may contain `seekTerm`.
      Returns:
        true if the next block is opened; false if there is no blocks anymore and the iteration is over.
      Throws:
        `IOException`

    - #### seekExact

          public boolean seekExact(BytesRef text)

      Overrides:
        `seekExact` in class `BlockReader`

    - #### seekExact

          public void seekExact(long ord)

      Description copied from class: `BlockReader`
      Not supported.
      Overrides:
        `seekExact` in class `BlockReader`

    - #### seekExact

          public void seekExact(BytesRef term,
                                TermState state)

      Description copied from class: `BlockReader`
      Positions this `BlockReader` without re-seeking the term dictionary.

      The block containing the term is not read by this method. It will be read lazily only if needed, for example if `BlockReader.next()` is called. Calling `BlockReader.postings(org.apache.lucene.index.PostingsEnum, int)` after this method does require the block to be read.

      Overrides:
        `seekExact` in class `BlockReader`

    - #### seekCeil

          public TermsEnum.SeekStatus seekCeil(BytesRef text)

      Overrides:
        `seekCeil` in class `BlockReader`

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