TokenSources (Lucene 2.4.1 API)
Keywords: org.apache.lucene.search.highlight.TokenSources class

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## org.apache.lucene.search.highlight
Class TokenSources

    java.lang.Object
      org.apache.lucene.search.highlight.TokenSources

    public class TokenSources

extends Object

Hides implementation issues associated with obtaining a TokenStream for use with the higlighter - can obtain from TermFreqVectors with offsets and (optionally) positions or from Analyzer class reparsing the stored content.

Constructor Summary
`TokenSources()`

Method Summary
`static TokenStream` | `getAnyTokenStream(IndexReader reader, int docId, String field, Analyzer analyzer)` A convenience method that tries a number of approaches to getting a token stream.
`static TokenStream` | `getAnyTokenStream(IndexReader reader, int docId, String field, Document doc, Analyzer analyzer)` A convenience method that tries to first get a TermPositionVector for the specified docId, then, falls back to using the passed in `Document` to retrieve the TokenStream.
`static TokenStream` | `getTokenStream(Document doc, String field, Analyzer analyzer)`
`static TokenStream` | `getTokenStream(IndexReader reader, int docId, String field)`
`static TokenStream` | `getTokenStream(IndexReader reader, int docId, String field, Analyzer analyzer)`
`static TokenStream` | `getTokenStream(String field, String contents, Analyzer analyzer)`
`static TokenStream` | `getTokenStream(TermPositionVector tpv)`
`static TokenStream` | `getTokenStream(TermPositionVector tpv, boolean tokenPositionsGuaranteedContiguous)` Low level api.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### TokenSources

    public TokenSources()

Method Detail

### getAnyTokenStream

    public static TokenStream getAnyTokenStream(IndexReader reader,
                                                int docId,
                                                String field,
                                                Document doc,
                                                Analyzer analyzer)
                                         throws IOException

  A convenience method that tries to first get a TermPositionVector for the specified docId, then, falls back to using the passed in `Document` to retrieve the TokenStream. This is useful when you already have the document, but would prefer to use the vector first.

  Parameters:
    `reader` - The `IndexReader` to use to try and get the vector from
    `docId` - The docId to retrieve.
    `field` - The field to retrieve on the document
    `doc` - The document to fall back on
    `analyzer` - The analyzer to use for creating the TokenStream if the vector doesn't exist
  Returns:
    The `TokenStream` for the `Fieldable` on the `Document`
  Throws:
    `IOException` - if there was an error loading

### getAnyTokenStream

    public static TokenStream getAnyTokenStream(IndexReader reader,
                                                int docId,
                                                String field,
                                                Analyzer analyzer)
                                         throws IOException

  A convenience method that tries a number of approaches to getting a token stream. The cost of finding there are no termVectors in the index is minimal (1000 invocations still registers 0 ms). So this "lazy" (flexible?) approach to coding is probably acceptable

  Parameters:
    `reader` -
    `docId` -
    `field` -
    `analyzer` -
  Returns:
    null if field not stored correctly
  Throws:
    `IOException`

### getTokenStream

    public static TokenStream getTokenStream(TermPositionVector tpv)

### getTokenStream

    public static TokenStream getTokenStream(TermPositionVector tpv,
                                             boolean tokenPositionsGuaranteedContiguous)

  Low level api. Returns a token stream or null if no offset info available in index. This can be used to feed the highlighter with a pre-parsed token stream In my tests the speeds to recreate 1000 token streams using this method are: - with TermVector offset only data stored - 420 milliseconds - with TermVector offset AND position data stored - 271 milliseconds (nb timings for TermVector with position data are based on a tokenizer with contiguous positions - no overlaps or gaps) The cost of not using TermPositionVector to store pre-parsed content and using an analyzer to re-parse the original content: - reanalyzing the original content - 980 milliseconds The re-analyze timings will typically vary depending on - 1) The complexity of the analyzer code (timings above were using a stemmer/lowercaser/stopword combo) 2) The number of other fields (Lucene reads ALL fields off the disk when accessing just one document field - can cost dear!) 3) Use of compression on field storage - could be faster cos of compression (less disk IO) or slower (more CPU burn) depending on the content.

  Parameters:
    `tpv` -
    `tokenPositionsGuaranteedContiguous` - true if the token position numbers have no overlaps or gaps. If looking to eek out the last drops of performance, set to true. If in doubt, set to false.

### getTokenStream

    public static TokenStream getTokenStream(IndexReader reader,
                                             int docId,
                                             String field)
                                      throws IOException

  Throws:
    `IOException`

### getTokenStream

    public static TokenStream getTokenStream(IndexReader reader,
                                             int docId,
                                             String field,
                                             Analyzer analyzer)
                                      throws IOException

  Throws:
    `IOException`

### getTokenStream

    public static TokenStream getTokenStream(Document doc,
                                             String field,
                                             Analyzer analyzer)

### getTokenStream

    public static TokenStream getTokenStream(String field,
                                             String contents,
                                             Analyzer analyzer)

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