Github user suez1224 commented on the issue:
https://github.com/apache/flink/pull/5355
@bowenli86 The following two features are related to this PR.
[CALCITE-2016] Make item + dot operators work for array (e.g. SELECT
orders[5].color FROM t (Shuyi Chen)
[CALCITE-1867] Allow user-defined grouped window functions (Timo Walther)
Also, Calcite 1.15 added built-in support for simple DDL statements like
CREATE and DROP.---
