Hi, Mark,

Mark Woodward wrote:

>>> My question, is it a syntactic technicality that PostgreSQL asks for a
>>> "group by," or a bug in the parser?
>> I think that it's a lack of special-casing the = operator. Imagine
>> "where ycis_id>15" or "where ycis_id @|< $RECTANGLE" or other (probably
>> user defined) operators on (probably user defined) datatypes.
>> The parser has no real knowledge what the operators do, it simply
>> requests one that returns a bool.
>> One could make the parser to special case the = operator, and maybe some
>> others, however I doubt it's worth the effort.
> I understand the SQL, and this isn't a "sql" question else it would be on
> a different list, it is a PostgreSQL internals question and IMHO potential
> bug.

And that's why I talked about PostgreSQL internals.

> The original query:
> select ycis_id, min(tindex), avg(tindex) from y where ycis_id = 15;
> Should NOT require a "group by" to get ycis_id in the results.

And, as I wrote, this is only possible when the query parser
special-cases the = operator (compared to all other operators).

Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in Europe! www.ffii.org

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