[postgis-devel] PG7.4 ordering operator

[strk]

Trying to figure out what the problem was, I've found this probably
wrong COMMUTATOR specifications in postgis_sql_common.sql.in:

        ( CURRENT COMMUTATOR SPEC )    ( PROPOSED UPDATE )
        A ~=  B     ==     B  =  A        [ B ~= A ]
        A  @  B     ==     B  @  A        [ B  ~ A ]
        A  >  B     ==     B  >  A        [ B  < A ]
        A  <  B     ==     B  <  A        [ B  > A ]

I'll check other clause to ensure correctness, but I won't commit
the changes until someone more inside will tell me about them.

See: http://www.postgresql.org/docs/7.4/interactive/xoper-optimization.html
for more infos about this keyword.

Here is a snippet:
> if you provide them, you must be sure that they are right!
> Incorrect use of an optimization clause can result in server
> process crashes, subtly wrong output, or other Bad Things.
> [...]
> Additional optimization clauses might be added in future versions
> of PostgreSQL. The ones described here are all the ones that
> release 7.4 understands. 

--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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