On Sat, Mar 20, 2021 at 3:05 PM Tomas Vondra <[email protected]> wrote: > > Hi, > > I think this bit in brin_tuple.c is wrong: > > ... > Form_pg_attribute att = TupleDescAttr(brdesc->bd_tupdesc, > keyno); > Datum cvalue = toast_compress_datum(value, > att->attcompression); > > The problem is that this is looking at the index descriptor (i.e. what > types are indexed) instead of the stored type. For BRIN those may be > only loosely related, which is why the code does this a couple lines above: > > /* We must look at the stored type, not at the index descriptor. */ > TypeCacheEntry *atttype > = brdesc->bd_info[keyno]->oi_typcache[datumno];
Ok, I was not aware of this. > For the built-in BRIN opclasses this happens to work, because e.g. > minmax stores two values of the original type. But it may not work for > other out-of-core opclasses, and it certainly doesn't work for the new > BRIN opclasses (bloom and minmax-multi). Okay > Unfortunately, the only thing we have here is the type OID, so I guess > the only option is using GetDefaultToastCompression(). Perhaps we might > include that into BrinOpcInfo too, in the future. Right, I think for now we can use default compression for this case. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com
