Re: Enabling Checksums

On 5 March 2013 18:02, Jeff Davis <pgsql@j-davis.com> wrote:

> Fletcher is probably significantly faster than CRC-16, because I'm just
> doing int32 addition in a tight loop.
>
> Simon originally chose Fletcher, so perhaps he has more to say.

IIRC the research showed Fletcher was significantly faster for only a
small loss in error detection rate.

It was sufficient to make our error detection > 1 million times
better, possibly more. That seems sufficient to enable early detection
of problems, since if we missed the first error, a second is very
likely to be caught (etc). So I am assuming that we're trying to catch
a pattern of errors early, rather than guarantee we can catch the very
first error.

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