Re: Online checksums patch - once again

> On 22 Jun 2020, at 18:29, Robert Haas  wrote:
> 
> On Mon, Jun 22, 2020 at 8:27 AM Daniel Gustafsson  wrote:
>> Restartability is implemented by keeping state in pg_class.  I opted for a bool
>> which is cleared as the first step of checksum enable, since it offers fewer
>> synchronization cornercases I think.
> 
> Unless you take AccessExclusiveLock on the table, this probably needs
> to be three-valued. Or maybe I am misunderstanding the design...

Sorry being a bit thick, can you elaborate which case you're thinking about?
CREATE TABLE sets the attribute according to the value of data_checksums, and
before enabling checksums (and before changing data_checksums to inprogress)
the bgworker will update all relhaschecksums from true (if any) to false.  Once
the state is set to inprogress all new relations will set relhaschecksums to
true.

The attached v19 fixes a few doc issues I had missed.

cheers ./daniel