On 2020-Nov-17, Simon Riggs wrote: > As an additional optimization, if we do find a row that needs freezing > on a data block, we should simply freeze *all* row versions on the > page, not just the ones below the selected cutoff. This is justified > since writing the block is the biggest cost and it doesn't make much > sense to leave a few rows unfrozen on a block that we are dirtying.
Yeah. We've had ealier proposals to use high and low watermarks: if any tuple is past the high watermark, then freeze all tuples that are past the low watermark. However this is ancient thinking (prior to HEAP_XMIN_FROZEN) and we don't need the low watermark to be different from zero, since the original xid is retained anyway. So +1 for this idea.
