[jira] [Created] (SOLR-4445) Join queries should execute their "from" queries on all shards

["Colin Bartolome (JIRA)" <ji...@apache.org>]

Colin Bartolome created SOLR-4445:
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             Summary: Join queries should execute their "from" queries on all shards
                 Key: SOLR-4445
                 URL: https://issues.apache.org/jira/browse/SOLR-4445
             Project: Solr
          Issue Type: Improvement
          Components: query parsers, SolrCloud
    Affects Versions: 4.1
            Reporter: Colin Bartolome


When running join queries on a collection with multiple shards, the "from" site of the query is executed on the shard that serves the request only, instead of on all shards. The matching documents are then passed to the "to" side of the query. This leads to the overall result set being a subset of what it would be, if the join query were run on a collection with only one shard.

That is, a four-shard collection will, on average, return 25% of the results a single-shard collection would.

The code should execute the "from" side of the query on all available shards before passing those matching documents to the "to" side of the query.

Note: [LUCENE-3759|https://issues.apache.org/jira/browse/LUCENE-3759] proposes an upgrade to {{JoinUtil}} to support joining where the documents matched by the "from" side of the query exist on multiple shards. Solr does not use that class for joining (nor does anything else?), so this would have to be implemented separately.

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