Re: [HACKERS] Pluggable storage

On Wed, Aug 23, 2017 at 11:05 AM, Haribabu Kommi

<kommi.haribabu@gmail.com> wrote:
>
>
> On Mon, Aug 21, 2017 at 7:25 PM, Amit Kapila <amit.kapila16@gmail.com>
> wrote:
>>
>> On Mon, Aug 21, 2017 at 12:58 PM, Haribabu Kommi
>> <kommi.haribabu@gmail.com> wrote:
>> >
>> > On Sun, Aug 13, 2017 at 5:17 PM, Amit Kapila <amit.kapila16@gmail.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.
>

It will be easy to understand and see if there is some better
alternative once you have something in the form of a patch.