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).
HTH,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
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