Re: general purpose array_sort

[Junwang Zhao]

On Wed, Oct 2, 2024 at 9:51 AM jian he <jian.universal...@gmail.com> wrote:
>
> > >
> > > + typentry = (TypeCacheEntry *) fcinfo->flinfo->fn_extra;
> > > + if (typentry == NULL || typentry->type_id != elmtyp)
> > > + {
> > > + typentry = lookup_type_cache(elmtyp, sort_asc ? TYPECACHE_LT_OPR :
> > > TYPECACHE_GT_OPR);
> > > + fcinfo->flinfo->fn_extra = (void *) typentry;
> > > + }
> > > you need to one-time check typentry->lt_opr or typentry->gt_opr exists?
> > > see CreateStatistics.
> > >             /* Disallow data types without a less-than operator */
> > >             type = lookup_type_cache(attForm->atttypid, TYPECACHE_LT_OPR);
> > >             if (type->lt_opr == InvalidOid)
> > >                 ereport(ERROR,
> > >                         (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
> > >                          errmsg("column \"%s\" cannot be used in
> > > statistics because its type %s has no default btree operator class",
> > >                                 attname, 
> > > format_type_be(attForm->atttypid))));
> >
> > I added an Assert for this part, not sure if that is enough.
> >
>
> i think it really should be:
>
> if (typentry == NULL || typentry->type_id != elmtyp)
> {
>  typentry = lookup_type_cache(elmtyp, sort_asc ? TYPECACHE_LT_OPR :
> TYPECACHE_GT_OPR);
>  fcinfo->flinfo->fn_extra = (void *) typentry;
> if ((sort_asc && !OidIsValid(typentry->lt_opr) || (!sort_as &&
> OidIsValid(typentry->gt_opr));
> ereport(ERROR,....)
> }
>
> Imagine a type that doesn't have TYPECACHE_LT_OPR or TYPECACHE_GT_OPR
> then we cannot do the sort, we should just error out.
>
> I just tried this colour type [1] with (CREATE TYPE colour (INPUT =
> colour_in, OUTPUT = colour_out, LIKE = pg_catalog.int4);
>
> select array_sort('{#FF0000, #FF0000}'::colour[]);
> of course it will segfault  with your new Assert.
>
>
> [1] https://github.com/hlinnaka/colour-datatype/blob/master/colour.c

Make sense, PFA v5 with Jian's suggestion.


-- 
Regards
Junwang Zhao

v5-0001-general-purpose-array_sort.patch
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