[CALCITE-3682] MaterializationService#defineMaterialization loses information on unique keys

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.21.0
• Component/s: core
• Assignee: Unassigned
• Reporter: Vladimir Sitnikov
• Created: 04/Jan/20 19:54
• Updated: 04/Jan/20 19:54

Description

The impacted test is testAggregateMaterializationOnCountDistinctQuery1

The test defines materialized view for the following SQL:

select deptno, empid, salary from emps group by deptno, empid, salary

In practice, the optimizer might be able to tell that empid is a unique key, thus it could understand the grouping is not needed.
However, when it defines a materialized view, it loses uniqueness information, so it declares the view as

select deptno, empid, salary from emps

and the uniqueness is not there.

org.apache.calcite.materialize.MaterializationService.DefaultTableFactory should probably compute metadata (e.g. unique keys, something else?) and propagate it to the materialized view.