Re: Online enabling of checksums

Greetings,

* Tomas Vondra (tomas(dot)vondra(at)2ndquadrant(dot)com) wrote:
> While looking at the online checksum verification patch (which I guess
> will get committed before this one), it occurred to me that disabling
> checksums may need to be more elaborate, to protect against someone
> using the stale flag value (instead of simply switching to "off"
> assuming that's fine).
>
> The signals etc. seem good enough for our internal stuff, but what if
> someone uses the flag in a different way? E.g. the online checksum
> verification runs as an independent process (i.e. not a backend) and
> reads the control file to find out if the checksums are enabled or not.
> So if we just switch from "on" to "off" that will break.
>
> Of course, we may also say "Don't disable checksums while online
> verification is running!" but that's not ideal.

I'm not really sure what else we could say here..? I don't particularly
see an issue with telling people that if they disable checksums while
they're running a tool that's checking the checksums that they're going
to get odd results.

Thanks!

Stephen