[postgis-devel] PG7.4 ordering operator

[strk]

Found the problem:
> When there is no default [B-tree] operator class for a data type,
> you will get errors like "could not identify an ordering operator"
> if you try to use these SQL features [DISTINCT, GROUP BY, ORDER BY]
> with the data type. 
> [...]
> Note:  In PostgreSQL versions before 7.4, sorting and grouping operations
> would implicitly use operators named =, <, and >. The new behavior of
> relying on default operator classes avoids having to make any assumption
> about the behavior of operators with particular names. 

So we need to define a default b-tree operatoc class in
postgis_sql_74_end.sql.in

--strk;

strk wrote:
> Testing postgis support in PG7.4 (2003-11-11)
> I've encountered to this problem:
> 
>         ERROR:  could not identify an ordering operator for type geometry
>         HINT:  Use an explicit ordering operator or modify the query.
> 
> Whenever I issue one of these commands:
> 
> 	gis=# select the_geom from table1 UNION select the_geom from table2;
> 	gis=# select DISTINCT the_geom from table1;
> 	gis=# select the_geom from table1 ORDER BY the_geom;
> 
> Operators '<', '>', '=' are available:
> 
> 	 oprname | leftoperand | rightoperand
> 	---------+-------------+--------------
> 	 <<      | geometry    | geometry
> 	 &<      | geometry    | geometry
> 	 &&      | geometry    | geometry
> 	 &>      | geometry    | geometry
> 	 >>      | geometry    | geometry
> 	 ~=      | geometry    | geometry
> 	 @       | geometry    | geometry
> 	 ~       | geometry    | geometry
> 	 =       | geometry    | geometry
> 	 <       | geometry    | geometry
> 	 >       | geometry    | geometry
> 	(11 rows)
> 
> Previous PG versions does not show this problem.
> Any hint on what might be missing ?
> 
> --strk;
> 
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