>
>Preconditions: debug build with DEV_BUILD macro defined.
>
>SELECT DISTINCT RDB$DESCRIPTION FROM RDB$RELATIONS;
>
>This results in an triggered assert
> assert (sort_key->skd_dtype != 0);
>at (or about) line 4287 in jrd/opt.c.

That's an invalid assertion - the engine is happy to
sort by a blob field - uses the blob id, so the results
aren't very interesting, but it does work. A better
solution would be to fix DSQL so its late parse phase
detects a nonsense operation and reports an error.

Ann