| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Cc: | Junji TERAMOTO <teramoto(dot)junji(at)lab(dot)ntt(dot)co(dot)jp>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Quick-and-dirty compression for WAL backup blocks |
| Date: | 2005-06-06 16:24:45 |
| Message-ID: | 4169.1118075085@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes:
> Vacuum doesn't zero out the free space between lower and upper,
It does now ;-)
> 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?
regards, tom lane
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