mirror of https://github.com/apache/druid.git
834aae096a
This PR does two things 1. It adds the capability to surface missing features in SQL to users - The calcite planner will explore through multiple rules to convert a logical SQL query to a druid native query. Some rules change the shape of the query itself, optimize it and some rules are responsible for translating the query into a druid native query. These are DruidQueryRule, DruidOuterQueryRule, DruidJoinRule, DruidUnionDataSourceRule, DruidUnionRule etc. These rules will look at SQL and will do the necessary transformation. But if the rule can't transform the query, it returns back the control to the calcite planner without recording why was it not able to transform. E.g. there is a join query with a non-equal join condition. DruidJoinRule will look at the condition, see that it is not supported, and return back the control. The reason can be that a query can be planned in many different ways so if one rule can't parse it, the query may still be parseable by other rules. In this PR, we are intercepting these gaps and passing them back to the user if the query could not be planned at all. 2. The said capability has been used to generate actionable errors for some common unsupported SQL features. However, not all possible errors are covered and we can keep adding more in the future. |
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