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  1. Solr
  2. SOLR-13749

Implement support for joining across collections with multiple shards ( XCJF )



    • New Feature
    • Status: Closed
    • Blocker
    • Resolution: Fixed
    • None
    • 8.6
    • None
    • None


      This ticket includes 2 query parsers.

      The first one is the "Cross collection join filter"  (XCJF) parser. This is the "Cross-collection join filter" query parser. It can do a call out to a remote collection to get a set of join keys to be used as a filter against the local collection.

      The second one is the Hash Range query parser that you can specify a field name and a hash range, the result is that only the documents that would have hashed to that range will be returned.

      This query parser will do an intersection based on join keys between 2 collections.

      The local collection is the collection that you are searching against.

      The remote collection is the collection that contains the join keys that you want to use as a filter.

      Each shard participating in the distributed request will execute a query against the remote collection.  If the local collection is setup with the compositeId router to be routed on the join key field, a hash range query is applied to the remote collection query to only match the documents that contain a potential match for the documents that are in the local shard/core.  


      Here's some vocab to help with the descriptions of the various parameters.

      Term Description
      Local Collection This is the main collection that is being queried.
      Remote Collection This is the collection that the XCJFQuery will query to resolve the join keys.
      XCJFQuery The lucene query that executes a search to get back a set of join keys from a remote collection
      HashRangeQuery The lucene query that matches only the documents whose hash code on a field falls within a specified range.



      Param  Required  Description
      collection Required The name of the external Solr collection to be queried to retrieve the set of join key values ( required )
      zkHost Optional The connection string to be used to connect to Zookeeper. 
      zkHost and solrUrl are both optional parameters, and at most one of them should be specified. 
      If neither of zkHost or solrUrl are specified, the local Zookeeper cluster will be used. ( optional )
      solrUrl Optional The URL of the external Solr node to be queried ( optional )
      from Required The join key field name in the external collection ( required )
      to Required The join key field name in the local collection
      v See Note The query to be executed against the external Solr collection to retrieve the set of join key values. 
      Note:  The original query can be passed at the end of the string or as the "v" parameter. 
      It's recommended to use query parameter substitution with the "v" parameter
      to ensure no issues arise with the default query parsers.
      routed   true / false.  If true, the XCJF query will use each shard's hash range to determine the set of join keys to retrieve for that shard.
      This parameter improves the performance of the cross-collection join, but
      it depends on the local collection being routed by the toField.  If this parameter is not specified,
      the XCJF query will try to determine the correct value automatically.
      ttl   The length of time that an XCJF query in the cache will be considered valid, in seconds.  Defaults to 3600 (one hour). 
      The XCJF query will not be aware of changes to the remote collection, so
      if the remote collection is updated, cached XCJF queries may give inaccurate results. 
      After the ttl period has expired, the XCJF query will re-execute the join against the remote collection.
      All others   Any normal Solr parameter can also be specified as a local param.


      Example Solr Config.xml changes:

      <cache name="hash_vin"
      <queryParser name="xcjf" class="org.apache.solr.search.join.XCJFQueryParserPlugin">
        <str name="routerField">vin</str>
      <queryParser name="hash_range" class="org.apache.solr.search.join.HashRangeQueryParserPlugin" />

      Example Usage:

      {!xcjf collection="otherCollection" from="fromField" to="toField" v="*:*"}





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          David Smiley

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