Package org.apache.lucene.search.grouping

## Class GroupingSearch

- java.lang.Object
- - org.apache.lucene.search.grouping.GroupingSearch

-     public class GroupingSearch
      extends Object

  Convenience class to perform grouping in a non distributed environment.
  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `GroupingSearch​(String groupField)` | Constructs a `GroupingSearch` instance that groups documents by index terms using DocValues.
    `GroupingSearch​(ValueSource groupFunction, Map<Object,​Object> valueSourceContext)` | Constructs a `GroupingSearch` instance that groups documents by function using a `ValueSource` instance.
    `GroupingSearch​(GroupSelector<?> groupSelector)` | Constructs a `GroupingSearch` instance that groups documents using a `GroupSelector`
    `GroupingSearch​(Query groupEndDocs)` | Constructor for grouping documents by doc block.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `GroupingSearch` | `disableCaching()` | Disables any enabled cache.
    `Bits` | `getAllGroupHeads()` | Returns the matching group heads if `setAllGroupHeads(boolean)` was set to true or an empty bit set.
    `<T> Collection<T>` | `getAllMatchingGroups()` | If `setAllGroups(boolean)` was set to `true` then all matching groups are returned, otherwise an empty collection is returned.
    `protected TopGroups<?>` | `groupByDocBlock​(IndexSearcher searcher, Query query, int groupOffset, int groupLimit)` |
    `protected TopGroups` | `groupByFieldOrFunction​(IndexSearcher searcher, Query query, int groupOffset, int groupLimit)` |
    `<T> TopGroups<T>` | `search​(IndexSearcher searcher, Query query, int groupOffset, int groupLimit)` | Executes a grouped search.
    `GroupingSearch` | `setAllGroupHeads​(boolean allGroupHeads)` | Whether to compute all group heads (most relevant document per group) matching the query.
    `GroupingSearch` | `setAllGroups​(boolean allGroups)` | Whether to also compute all groups matching the query.
    `GroupingSearch` | `setCaching​(int maxDocsToCache, boolean cacheScores)` | Enables caching for the second pass search.
    `GroupingSearch` | `setCachingInMB​(double maxCacheRAMMB, boolean cacheScores)` | Enables caching for the second pass search.
    `GroupingSearch` | `setGroupDocsLimit​(int groupDocsLimit)` | Specifies the number of documents to return inside a group from the specified groupDocsOffset.
    `GroupingSearch` | `setGroupDocsOffset​(int groupDocsOffset)` | Specifies the offset for documents inside a group.
    `GroupingSearch` | `setGroupSort​(Sort groupSort)` | Specifies how groups are sorted.
    `GroupingSearch` | `setIncludeMaxScore​(boolean includeMaxScore)` | Whether to include the score of the most relevant document per group.
    `GroupingSearch` | `setSortWithinGroup​(Sort sortWithinGroup)` | Specified how documents inside a group are sorted.

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

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

- - ### Constructor Detail

    - #### GroupingSearch

          public GroupingSearch​(String groupField)

      Constructs a `GroupingSearch` instance that groups documents by index terms using DocValues. The group field can only have one token per document. This means that the field must not be analysed.
      Parameters:
        `groupField` - The name of the field to group by.

    - #### GroupingSearch

          public GroupingSearch​(GroupSelector<?> groupSelector)

      Constructs a `GroupingSearch` instance that groups documents using a `GroupSelector`
      Parameters:
        `groupSelector` - a `GroupSelector` that defines groups for this GroupingSearch

    - #### GroupingSearch

          public GroupingSearch​(ValueSource groupFunction,
                                Map<Object,​Object> valueSourceContext)

      Constructs a `GroupingSearch` instance that groups documents by function using a `ValueSource` instance.
      Parameters:
        `groupFunction` - The function to group by specified as `ValueSource`
        `valueSourceContext` - The context of the specified groupFunction

    - #### GroupingSearch

          public GroupingSearch​(Query groupEndDocs)

      Constructor for grouping documents by doc block. This constructor can only be used when documents belonging in a group are indexed in one block.
      Parameters:
        `groupEndDocs` - The query that marks the last document in all doc blocks

  - ### Method Detail

    - #### search

          public <T> TopGroups<T> search​(IndexSearcher searcher,
                                         Query query,
                                         int groupOffset,
                                         int groupLimit)
                                  throws IOException

      Executes a grouped search. Both the first pass and second pass are executed on the specified searcher.
      Parameters:
        `searcher` - The `IndexSearcher` instance to execute the grouped search on.
        `query` - The query to execute with the grouping
        `groupOffset` - The group offset
        `groupLimit` - The number of groups to return from the specified group offset
      Returns:
        the grouped result as a `TopGroups` instance
      Throws:
        `IOException` - If any I/O related errors occur

    - #### groupByFieldOrFunction

          protected TopGroups groupByFieldOrFunction​(IndexSearcher searcher,
                                                     Query query,
                                                     int groupOffset,
                                                     int groupLimit)
                                              throws IOException

      Throws:
        `IOException`

    - #### groupByDocBlock

          protected TopGroups<?> groupByDocBlock​(IndexSearcher searcher,
                                                 Query query,
                                                 int groupOffset,
                                                 int groupLimit)
                                          throws IOException

      Throws:
        `IOException`

    - #### setCachingInMB

          public GroupingSearch setCachingInMB​(double maxCacheRAMMB,
                                               boolean cacheScores)

      Enables caching for the second pass search. The cache will not grow over a specified limit in MB. The cache is filled during the first pass searched and then replayed during the second pass searched. If the cache grows beyond the specified limit, then the cache is purged and not used in the second pass search.
      Parameters:
        `maxCacheRAMMB` - The maximum amount in MB the cache is allowed to hold
        `cacheScores` - Whether to cache the scores
      Returns:
        `this`

    - #### setCaching

          public GroupingSearch setCaching​(int maxDocsToCache,
                                           boolean cacheScores)

      Enables caching for the second pass search. The cache will not contain more than the maximum specified documents. The cache is filled during the first pass searched and then replayed during the second pass searched. If the cache grows beyond the specified limit, then the cache is purged and not used in the second pass search.
      Parameters:
        `maxDocsToCache` - The maximum number of documents the cache is allowed to hold
        `cacheScores` - Whether to cache the scores
      Returns:
        `this`

    - #### disableCaching

          public GroupingSearch disableCaching()

      Disables any enabled cache.
      Returns:
        `this`

    - #### setGroupSort

          public GroupingSearch setGroupSort​(Sort groupSort)

      Specifies how groups are sorted. Defaults to `Sort.RELEVANCE`.
      Parameters:
        `groupSort` - The sort for the groups.
      Returns:
        `this`

    - #### setSortWithinGroup

          public GroupingSearch setSortWithinGroup​(Sort sortWithinGroup)

      Specified how documents inside a group are sorted. Defaults to `Sort.RELEVANCE`.
      Parameters:
        `sortWithinGroup` - The sort for documents inside a group
      Returns:
        `this`

    - #### setGroupDocsOffset

          public GroupingSearch setGroupDocsOffset​(int groupDocsOffset)

      Specifies the offset for documents inside a group.
      Parameters:
        `groupDocsOffset` - The offset for documents inside a
      Returns:
        `this`

    - #### setGroupDocsLimit

          public GroupingSearch setGroupDocsLimit​(int groupDocsLimit)

      Specifies the number of documents to return inside a group from the specified groupDocsOffset.
      Parameters:
        `groupDocsLimit` - The number of documents to return inside a group
      Returns:
        `this`

    - #### setIncludeMaxScore

          public GroupingSearch setIncludeMaxScore​(boolean includeMaxScore)

      Whether to include the score of the most relevant document per group.
      Parameters:
        `includeMaxScore` - Whether to include the score of the most relevant document per group
      Returns:
        `this`

    - #### setAllGroups

          public GroupingSearch setAllGroups​(boolean allGroups)

      Whether to also compute all groups matching the query. This can be used to determine the number of groups, which can be used for accurate pagination.

      When grouping by doc block the number of groups are automatically included in the `TopGroups` and this option doesn't have any influence.

      Parameters:
        `allGroups` - to also compute all groups matching the query
      Returns:
        `this`

    - #### getAllMatchingGroups

          public <T> Collection<T> getAllMatchingGroups()

      If `setAllGroups(boolean)` was set to `true` then all matching groups are returned, otherwise an empty collection is returned.
      Type Parameters:
        `T` - The group value type. This can be a `BytesRef` or a `MutableValue` instance. If grouping by doc block this the group value is always `null`.
      Returns:
        all matching groups are returned, or an empty collection

    - #### setAllGroupHeads

          public GroupingSearch setAllGroupHeads​(boolean allGroupHeads)

      Whether to compute all group heads (most relevant document per group) matching the query.

      This feature isn't enabled when grouping by doc block.

      Parameters:
        `allGroupHeads` - Whether to compute all group heads (most relevant document per group) matching the query
      Returns:
        `this`

    - #### getAllGroupHeads

          public Bits getAllGroupHeads()

      Returns the matching group heads if `setAllGroupHeads(boolean)` was set to true or an empty bit set.
      Returns:
        The matching group heads if `setAllGroupHeads(boolean)` was set to true or an empty bit set