Package org.apache.lucene.search.suggest.fst

Class WFSTCompletionLookup

java.lang.Object
org.apache.lucene.search.suggest.Lookup
org.apache.lucene.search.suggest.fst.WFSTCompletionLookup
public class WFSTCompletionLookup extends Lookup
Suggester based on a weighted FST: it first traverses the prefix, then walks the n shortest paths to retrieve top-ranked suggestions.

NOTE: Input weights must be between 0 and Integer.MAX_VALUE, any other values will be rejected.

  • Constructor Details

    • WFSTCompletionLookup

      public WFSTCompletionLookup()
      Calls WFSTCompletionLookup(true)

    • WFSTCompletionLookup

      public WFSTCompletionLookup(boolean exactFirst)
      Creates a new suggester.
      Parameters:
      exactFirst - true if suggestions that match the prefix exactly should always be returned first, regardless of score. This has no performance impact, but could result in low-quality suggestions.

  • Method Details

    • build

      public void build(InputIterator iterator) throws IOException
      Description copied from class: Lookup
      Builds up a new internal Lookup representation based on the given InputIterator. The implementation might re-sort the data internally.
      Specified by:
      build in class Lookup
      Throws:
      IOException

    • store

      public boolean store(DataOutput output) throws IOException
      Description copied from class: Lookup
      Persist the constructed lookup data to a directory. Optional operation.
      Specified by:
      store in class Lookup
      Parameters:
      output - DataOutput to write the data to.
      Returns:
      true if successful, false if unsuccessful or not supported.
      Throws:
      IOException - when fatal IO error occurs.

    • load

      public boolean load(DataInput input) throws IOException
      Description copied from class: Lookup
      Discard current lookup data and load it from a previously saved copy. Optional operation.
      Specified by:
      load in class Lookup
      Parameters:
      input - the DataInput to load the lookup data.
      Returns:
      true if completed successfully, false if unsuccessful or not supported.
      Throws:
      IOException - when fatal IO error occurs.

    • lookup

      public List<Lookup.LookupResult> lookup(CharSequence key, boolean onlyMorePopular, int num)
      Description copied from class: Lookup
      Look up a key and return possible completion for this key.
      Specified by:
      lookup in class Lookup
      Parameters:
      key - lookup key. Depending on the implementation this may be a prefix, misspelling, or even infix.
      onlyMorePopular - return only more popular results
      num - maximum number of results to return
      Returns:
      a list of possible completions, with their relative weight (e.g. popularity)

    • get

      public Object get(CharSequence key)
      Returns the weight associated with an input string, or null if it does not exist.

    • sizeInBytes

      public long sizeInBytes()
      Returns byte size of the underlying FST.
      Specified by:
      sizeInBytes in class Lookup
      Returns:
      ram size of the lookup implementation in bytes

    • getCount

      public long getCount()
      Description copied from class: Lookup
      Get the number of entries the lookup was built with
      Specified by:
      getCount in class Lookup
      Returns:
      total number of suggester entries