SQL: Allow MIN() and MAX() aggregate functions to operate also on arguments of type keyword

[MagnusAnde]

Allow MIN() and MAX() aggregate functions to operate
also on arguments of type keyword (and eventually also text) apart from the numeric and date.

This would simplify queries using GROUP BY returning columns of type keyword (and eventually text) that is not part of the group by statement. This would also harmonize with the expected behavior from persons used to sql in for example Sql Server.

select max(fieldOfTypeKeyword) from someIndex group by otherFieldOfTypeKeyword

This would return the last value in alphabetic order for the field fieldOfTypeKeyword in the group defined by the group by statement. The min() function would do the inverse.

[elasticmachine]

Pinging @elastic/es-search-aggs

[costin]

added minor formatting to your post

Thanks for the suggestion. This would essentially translate MAX and MIN into a more generic FIRST and LAST aggregate function (as it expands beyond numeric types and thus their meaning is slightly different).

We could support this through a terms agg with a size of 1.