Re: Track Oldest Initialized WAL Buffer Page

On Tue, Feb 07, 2023 at 07:30:00PM +0530, Bharath Rupireddy wrote:
> + /*
> + * Try updating oldest initialized XLog buffer page.
> + *
> + * Update it if we are initializing an XLog buffer page for the first
> + * time or if XLog buffers are full and we are wrapping around.
> + */
> + if (XLogRecPtrIsInvalid(XLogCtl->OldestInitializedPage) ||
> + (!XLogRecPtrIsInvalid(XLogCtl->OldestInitializedPage) &&
> + XLogRecPtrToBufIdx(XLogCtl->OldestInitializedPage) == nextidx))
> + {
> + Assert(XLogCtl->OldestInitializedPage < NewPageBeginPtr);
> +
> + XLogCtl->OldestInitializedPage = NewPageBeginPtr;
> + }

nitpick: I think you can simplify the conditional to

if (XLogRecPtrIsInvalid(XLogCtl->OldestInitializedPage) ||
XLogRecPtrToBufIdx(XLogCtl->OldestInitializedPage) == nextidx)

It's confusing to me that OldestInitializedPage is set to NewPageBeginPtr.
Doesn't that set it to the beginning of the newest initialized page?

--
Nathan Bossart
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