On Mon, 6 Jun 2005, Tom Lane wrote:
Heikki Linnakangas <[EMAIL PROTECTED]> writes:
Vacuum doesn't zero out the free space between lower and upper,
It does now ;-)
Oh :). Does it affect vacuum performance?
How about adding a flag to XLogRecData to indicate if the space between
pd_lower and pd_upper is meaningful or not? The XLogInsert caller probably
knows that. That way you could completely skip over the free space if
it's not meaningful, saving even more cycles.
Hmm ... that might not be a bad idea. As far as I can think offhand,
all the XLogInsert callers know very well what type of page they are
working with, so they would always be able to set such a flag correctly.
Would this be institutionalizing a particular approach to data
compression in the XLogInsert API, though?
The "skip the free space" optimization is still useful and worthwhile
even if we have a more sophisticated compression method for the
rest of the page.
- Heikki
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