quote from https://www.postgresql.org/docs/current/sql-select.html
The elements of the PARTITION BY list are interpreted in much the same
> fashion as elements of a GROUP BY
> <https://www.postgresql.org/docs/current/sql-select.html#SQL-GROUPBY>
> clause, except that they are always simple expressions and never the name
> or number of an output column.
>
I think "number of an output column" refers to "ordinal number of an output
column".
--
I recommend David Deutsch's <<The Beginning of Infinity>>
Jian