Re: Teach pg_receivewal to use lz4 compression

On Mon, Nov 22, 2021 at 09:02:47AM -0500, Robert Haas wrote:
> On Mon, Nov 22, 2021 at 12:46 AM Jeevan Ladhe
> <jeevan.ladhe@enterprisedb.com> wrote:
>> Fair enough. But, still I have a doubt in mind what benefit would that
>> really bring to us here, because we are immediately also freeing the
>> lz4buf without using it anywhere.
>
> Yeah, I'm also doubtful about that. If we're freeng the compression
> context, we shouldn't need to guarantee that it's in any particular
> state before doing so. Why would any critical cleanup be part of
> LZ4F_compressEnd() rather than LZ4F_freeCompressionContext()? The
> point of LZ4F_compressEnd() is to make sure all of the output bytes
> get written, and it would be stupid to force people to write the
> output bytes even when they've decided that they no longer care about
> them due to some error.

Hmm.  I have double-checked all that, and I agree that we could just
skip LZ4F_compressEnd() in this error code path.  From what I can see
in the upstream code, what we have now is not broken either, but the
compressEnd() call does some work that's not needed here.