Re: VACUUM (DISABLE_PAGE_SKIPPING on)

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.