Re: FAQ (disk space)

Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> On Mon, Jan 26, 2004 at 10:48:55AM +0000, Einar Indridason wrote:
>> Would it be worth it to calculate some sort of a checksum over a row, and
>> store that checksum along with the row?

> There has been discussion about checksumming entire pages and AFAIK they are
> in the WAL, I just don't think they in the main data store.

This has been discussed, as Martijn says, and I believe the consensus
was that the benefits wouldn't exceed the costs. Note that a checksum
does not magically prevent errors, it just means that you will detect
errors and refuse to access potentially-corrupt data. In practice there
are other ways to detect errors (eg, cross-checking of page header
fields) that seem to get the job done for us. Also, even when you do
have a corrupted page, having the system refuse to touch it at all is
not necessarily the behavior you want --- you're going to want to see
what data you can extract.

regards, tom lane