Package org.apache.lucene.monitor

# Class ParallelMatcher<T extends QueryMatch>

java.lang.Object
org.apache.lucene.monitor.CandidateMatcher<T>
org.apache.lucene.monitor.ParallelMatcher<T>

Type Parameters:
  `T` - the QueryMatch type returned

public class ParallelMatcher<T extends QueryMatch> extends CandidateMatcher<T>
Matcher class that runs matching queries in parallel.

This class delegates the actual matching to separate CandidateMatcher classes, built from a passed in MatcherFactory.

Use this when individual queries can take a long time to run, and you want to minimize latency. The matcher distributes queries amongst its worker threads using a BlockingQueue, and synchronization overhead may affect performance if the individual queries are very fast.

See Also:
  - `PartitionMatcher`

- ## Field Summary

  ### Fields inherited from class org.apache.lucene.monitor.CandidateMatcher

  `searcher`

- ## Method Summary

  Modifier and Type
  Method
  Description
  `protected void`
  `doFinish()`
  Called when all monitoring of a batch of documents is complete
  `static <T extends QueryMatch>
  MatcherFactory<T>`
  `factory(ExecutorService executor, MatcherFactory<T> matcherFactory)`
  Create a new MatcherFactory for a ParallelMatcher
  `static <T extends QueryMatch>
  MatcherFactory<T>`
  `factory(ExecutorService executor, MatcherFactory<T> matcherFactory, int threads)`
  Create a new MatcherFactory for a ParallelMatcher
  `void`
  `matchQuery(String queryId, Query matchQuery, Map<String,String> metadata)`
  Runs the supplied query against this CandidateMatcher's set of documents, storing any resulting match, and recording the query in the presearcher hits
  `T`
  `resolve(T match1, T match2)`
  If two matches from the same query are found (for example, two branches of a disjunction), combine them.

  ### Methods inherited from class org.apache.lucene.monitor.CandidateMatcher

  `addMatch, copyMatches, finish, reportError`

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

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

- ## Method Details

  - ### matchQuery

    public void matchQuery(String queryId, Query matchQuery, Map<String,String> metadata) throws IOException
    Description copied from class: `CandidateMatcher`
    Runs the supplied query against this CandidateMatcher's set of documents, storing any resulting match, and recording the query in the presearcher hits
    Specified by:
      `matchQuery` in class `CandidateMatcher<T extends QueryMatch>`
    Parameters:
      `queryId` - the query id
      `matchQuery` - the query to run
      `metadata` - the query metadata
    Throws:
      `IOException` - on IO errors

  - ### resolve

    public T resolve(T match1, T match2)
    Description copied from class: `CandidateMatcher`
    If two matches from the same query are found (for example, two branches of a disjunction), combine them.
    Specified by:
      `resolve` in class `CandidateMatcher<T extends QueryMatch>`
    Parameters:
      `match1` - the first match found
      `match2` - the second match found
    Returns:
      a Match object that combines the two

  - ### doFinish

    protected void doFinish()
    Description copied from class: `CandidateMatcher`
    Called when all monitoring of a batch of documents is complete
    Overrides:
      `doFinish` in class `CandidateMatcher<T extends QueryMatch>`

  - ### factory

    public static <T extends QueryMatch> MatcherFactory<T> factory(ExecutorService executor, MatcherFactory<T> matcherFactory, int threads)
    Create a new MatcherFactory for a ParallelMatcher
    Type Parameters:
      `T` - the type of QueryMatch generated
    Parameters:
      `executor` - the ExecutorService to use
      `matcherFactory` - the MatcherFactory to use to create submatchers
      `threads` - the number of threads to use

  - ### factory

    public static <T extends QueryMatch> MatcherFactory<T> factory(ExecutorService executor, MatcherFactory<T> matcherFactory)
    Create a new MatcherFactory for a ParallelMatcher

    This factory will create a ParallelMatcher that uses as many threads as there are cores available to the JVM (as determined by `Runtime.getRuntime().availableProcessors()`).

    Type Parameters:
      `T` - the type of QueryMatch generated
    Parameters:
      `executor` - the ExecutorService to use
      `matcherFactory` - the MatcherFactory to use to create submatchers