Re: refactoring relation extension and BufferAlloc(), faster COPY

On Tue, 10 Jan 2023 at 15:08, Andres Freund <andres@anarazel.de> wrote:
> Thanks for letting me now. Updated version attached.

I'm not too sure I've qualified for giving a meaningful design review
here, but I have started looking at the patches and so far only made
it as far as 0006.

I noted down the following while reading:

v2-0001:

1. BufferCheckOneLocalPin needs a header comment

v2-0002:

2. The following comment and corresponding code to release the
extension lock has been moved now.

/*
* Release the file-extension lock; it's now OK for someone else to extend
* the relation some more.
*/

I think it's worth detailing out why it's fine to release the
extension lock in the new location. You've added detail to the commit
message but I think you need to do the same in the comments too.

v2-0003

3. FileFallocate() and FileZero() should likely document what they
return, i.e zero on success and non-zero on failure.

4. I'm not quite clear on why you've modified FileGetRawDesc() to call
FileAccess() twice.

v2-0004:

5. Is it worth having two versions of PinLocalBuffer() one to adjust
the usage count and one that does not? Couldn't the version that does
not adjust the count skip doing pg_atomic_read_u32()?

v2-0005
v2-0006

David