Re: Skip hole in log_newpage

Hi,

On 2013-12-03 13:03:41 +0200, Heikki Linnakangas wrote:
> The log_newpage function, used to WAL-log a full copy of a page, is missing
> the trick we normally use for full-page images to leave out the unused space
> on the block. That's pretty trivial to implement, so we should.
>
> The place where this matters the most is when building a new B-tree index.
> When wal_level > minimal, all pages in the created index are logged with
> log_newpage, and by default we leave 10% free space on index pages. So
> implementing this reduces the amount of WAL generated by index creation by
> roughly 10%.

Sounds like a good idea to me.

> Anyone see a problem with this?

I haven't looked thoroughly through all callsites, but shouldn't the
vacuumlazy callsite use std = true?

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services