[multistage] Add Support for Multi-Group Queries for Window Functions

[ankitsultana]

Queries with multiple partition-by clauses are not supported yet. Example:

SELECT
  ROW_NUMBER() OVER (
        PARTITION BY uuid,
        path,
        ORDER BY
          inserted_at DESC
      ) AS rn,
      RANK() OVER (
        PARTITION BY uuid
        ORDER BY
          inserted_at DESC
      ) AS rk
FROM tbl

The query above fails with the following error which comes from the window exchange node insert rule.

QueryPlanningError: Error optimizing query: Currently only 1 window group is supported, query has 2 groups

One way to tackle such a scenario is to break a Window operator into consecutive operators that run one after another and compute the different window functions. (Presto also does this)

Link:

pinot/pinot-query-planner/src/main/java/org/apache/pinot/calcite/rel/rules/PinotWindowExchangeNodeInsertRule.java

Line 236 in 43ee0f3

String.format("Currently only 1 window group is supported, query has %d groups", numGroups));

cc: @somandal

[wirybeaver]

@ankitsultana Hi Ankit, can I work on this task as a ramp up? I have deeply reviewed several MSE optimizer PRs.