Re: [HACKERS] Pluggable storage - Mailing list pgsql-hackers

On Thu, Jan 4, 2018 at 10:00 AM, Alexander Korotkov <a.korotkov@postgrespro.ru> wrote:

On Wed, Jan 3, 2018 at 10:08 AM, Haribabu Kommi <kommi.haribabu@gmail.com> wrote:

Apart from rebase, Added storage shared memory API, currently this API is used

only by the syncscan. And also all the exposed functions of syncscan usage is

removed outside the heap.

This makes me uneasy.  You introduce two new hooks for size estimation and initialization

of shared memory needed by storage am's.  But if storage am is implemented in shared library,

then this shared library can use our generic method for allocation of shared memory

(including memory needed by storage am).  If storage am is builtin, then hooks are also not

needed, because we know all our builtin storage am's in advance.  For me, it would be

nice to encapsulate heap am requirements in shared memory into functions like

HeapAmShmemSize() and HeapAmShmemInit(), and don't explicitly show outside that

this memory is needed for synchronized scan.  But separate hooks don't look justified for me.

Yes, I agree that for the builtin storage's there is no need of hooks. But in future,

if we want to support multiple storage's in an instance, we may need hooks for shared memory

registration. I am fine to change it.