[CALCITE-4972]: Review request + first time intro

[Mark Grey <mg...@spotify.com.INVALID>]

Hello Calcite community,

Taking the opportunity here to do an intro as a first time prospective
contributor!  I'm Mark, a data engineer from the northeastern US.

I've been a user of Calcite's query parsing and relational algebra
generation capabilities for several months but only just recently started
to attempt hacking on Calcite itself.

Following up on a discussion in the mailing list I filed CALCITE-4972
<https://issues.apache.org/jira/browse/CALCITE-4972>, and subsequently
attempted a patch for it <https://github.com/apache/calcite/pull/2683> as a
potentially newbie-friendly task.  Reviews are much appreciated!  The
internals of the SqlValidator are quite new to me.

My JIRA username is *mgthesecond*

Thanks,

Mark