Re: Enabling Checksums

On Tue, Mar 19, 2013 at 3:52 PM, Greg Smith <greg(at)2ndquadrant(dot)com> wrote:
> On 3/19/13 6:08 PM, Ants Aasma wrote:
>>
>> My main worry is that there is a reasonably
>> large population of users out there that don't have that acceleration
>> capability and will have to settle for performance overhead 4x worse
>> than what you currently measured for a shared buffer swapping
>> workload.
>
>
> That would be very bad. I want to keep hammering on this part of the
> implementation. If the only style of checksum that's computationally
> feasible is the Fletcher one that's already been done--if that approach is
> basically the most expensive one that's practical to use--I'd still consider
> that a major win over doing nothing.
>
> While being a lazy researcher today instead of writing code, I discovered
> that the PNG file format includes a CRC-32 on its data chunks, and to
> support that there's a CRC32 function inside of zlib:
> http://www.zlib.net/zlib_tech.html
>
> Is there anywhere that compiles a PostgreSQL --without-zlib that matters?

I'm confused. Postgres includes a CRC32 implementation for WAL, does
it not? Are you referring to something else?

I happen to remember this because I moved some things around to enable
third party programs (like xlogdump) to be separately compiled:
http://www.postgresql.org/message-id/E1S2Xo0-0004uv-FW@gemulon.postgresql.org

--
fdr