In article <25983.1260468559@sss.pgh.pa.us>,
Tom Lane <tgl@sss.pgh.pa.us> writes:
> The SQL standard says the default name for any output column other
> than a simple column reference is implementation-dependent. I think
> our implementation involves looking at the default value for a CASE.
Thanks for the clarification, Tom - so it's not a PostgreSQL bug, but
a misfeature of the SQL standard.
That being said, I still think that PostgreSQL could do better - how
about naming expression columns so that they are distinct from column
names? The current implementation throws an error e.g. for
SELECT adr, CASE lag(adr) OVER (ORDER BY adr) WHEN adr THEN NULL ELSE adr END, usr,
count(*)FROM tbl WHERE host = 'h1' GROUP BY adr, usr ORDER BY adr, usr
namely `ORDER BY "adr" is ambiguous' which I find somewhat confusing.
