AW: AW: pg_index.indislossy

> > > > > > > Can someone tell me what we use indislossy for?
> > > >
> > > > Ok, so the interpretation of this field is:
> > > >     A match in the index needs to be reevaluated in the heap tuple data,
> > > >     since a match in the index does not necessarily mean, that the heap tuple
> > > >     matches.
> > > >     If the heap tuple data matches, the index must always match.
> > 
> > AFAIK, this is true for all indexes in PostgreSQL, because index rows
> > don't store the transactions status.  Of course those are two different
> > underlying reasons why a heap lookup is always necessary, but there
> > shouldn't be any functional difference in the current implementation.
> 
> Seems it is something they added for the index abstraction and not for
> practical use by PostgreSQL.

Why, you do not need to call the comparison function on the heap data
if the index is not lossy, saves some CPU cycles.

Andreas