Re: Pluggable storage

On Mon, Aug 21, 2017 at 7:25 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:

> On Mon, Aug 21, 2017 at 12:58 PM, Haribabu Kommi
> <kommi(dot)haribabu(at)gmail(dot)com> wrote:
> >
> > On Sun, Aug 13, 2017 at 5:17 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> > wrote:
> >>
> >>
> >> Also, it is quite possible that some of the storage Am's don't even
> >> want to return bool as a parameter from HeapTupleSatisfies* API's. I
> >> guess what we need here is to provide a way so that different storage
> >> am's can register their function pointer for an equivalent to
> >> satisfies function. So, we need to change
> >> SnapshotData.SnapshotSatisfiesFunc in some way so that different
> >> handlers can register their function instead of using that directly.
> >> I think that should address the problem you are planning to solve by
> >> omitting buffer parameter.
> >
> >
> > Thanks for your suggestion. Yes, it is better to go in the direction of
> > SnapshotSatisfiesFunc.
> >
> > I verified the above idea of implementing the Tuple visibility functions
> > and assign them into the snapshotData structure based on the snapshot.
> >
> > The Tuple visibility functions that are specific to the relation are
> > available
> > with the RelationData structure and this structure may not be available,
> >
>
> Which functions are you referring here? I don't see anything in
> tqual.h that uses RelationData.

With storage API's, the tuple visibility functions are available with
RelationData
and those are needs used to update the SnapshotData structure
SnapshotSatisfiesFunc member.

But the RelationData is not available everywhere, where the snapshot is
created,
but it is available every place where the tuple visibility is checked. So I
just changed
the way of checking the tuple visibility with the information of snapshot
by calling
the corresponding tuple visibility function from RelationData.

If SnapshotData provides MVCC, then the MVCC specific tuple visibility
function from
RelationData is called. The SnapshotSatisfiesFunc member is changed to a
enum
that holds the tuple visibility type such as MVCC, DIRTY, SELF and etc.
Whenever
the visibility check is needed, the corresponding function is called.

Regards,
Hari Babu
Fujitsu Australia