[postgis-devel] PG7.4 ordering operator
strk
strk at keybit.net
Wed Nov 19 04:31:50 PST 2003
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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