Function XLogCheckBufferNeedsBackup

src/backend/access/transam/xloginsert.c:922–937

* Determine whether the buffer referenced has to be backed up. * * Since we don't yet have the insert lock, fullPageWrites and forcePageWrites * could change later, so the result should be used for optimization purposes * only. */

 * only.
 */
bool
XLogCheckBufferNeedsBackup(Buffer buffer)
{
	XLogRecPtr	RedoRecPtr;
	bool		doPageWrites;
	Page		page;

	GetFullPageWriteInfo(&RedoRecPtr, &doPageWrites);

	page = BufferGetPage(buffer);

	if (doPageWrites && PageGetLSN(page) <= RedoRecPtr)
		return true;			/* buffer requires backup */

	return false;				/* buffer does not need to be backed up */
}

/*
 * Write a backup block if needed when we are setting a hint. Note that