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

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: druid-adapter
• Assignee: Unassigned
• Reporter: Julian Hyde
• Created: 01/Jun/17 19:04
• Updated: 22/Feb/19 01:22

Description

Push Join down to Druid, using Druid's query-time lookup feature. As of Druid 0.10 this feature is marked experimental.

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.

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, and it knows the name of that lookup, then it could translate to a JDBC lookup in Druid.