[jira] [Created] (CALCITE-1823) Push join down to Druid, using Druid's query-time lookups

["Julian Hyde (JIRA)" <ji...@apache.org>]

Julian Hyde created CALCITE-1823:
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             Summary: Push join down to Druid, using Druid's query-time lookups
                 Key: CALCITE-1823
                 URL: https://issues.apache.org/jira/browse/CALCITE-1823
             Project: Calcite
          Issue Type: Bug
          Components: druid
            Reporter: Julian Hyde
            Assignee: Julian Hyde


Push Join down to Druid, using Druid's [query-time lookup|http://druid.io/docs/latest/querying/lookups.html] feature. As of Druid 0.10 this feature is marked experimental. 

bq. Very small lookups (count of keys on the order of a few dozen to a few hundred) can be passed at query time as a "map" lookup

We could use map lookups for joins to a Values operator.

bq. Globally cached lookups from local files, remote URIs, or JDBC through lookups-cached-global.

If Calcite sees a Join between Druid and a table in a JDBC data source, and it knows that that table is [registered as a lookup in Druid's schema|http://druid.io/docs/latest/development/extensions-core/lookups-cached-global.html], and it knows the name of that lookup, then it could translate to a JDBC lookup in Druid. 



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