56 make columns clause optional

[Dtenwolde]

Similar to DuckDB's parser where the SELECT is optional, omitting it implies a SELECT *, the COLUMNS clause is now also optional. This creates a COLUMNS(*) which returns all the columns, it also allows you to not repeat the columns explicitly in case you want to use them in the outer SELECT clause i.c.w. an aggregate or additional filter.

Sidenote: Also the trailing comma no longer leads to a parser error. COLUMNS(p.id,) is allowed for instance.

The simplest example:

-FROM GRAPH_TABLE (snb MATCH (p:Person)) limit 1

Equal to

FROM person
limit 1