Re: Read Uncommitted

On Wed, 18 Dec 2019 at 19:29, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:

> On 18/12/2019 20:46, Mark Dilger wrote:
> > On 12/18/19 10:06 AM, Simon Riggs wrote:
> >> Just consider this part of the recovery toolkit.
> >
> > In that case, don't call it "read uncommitted". Call it some other
> > thing entirely. Users coming from other databases may request
> > "read uncommitted" isolation expecting something that works.
> > Currently, that gets promoted to "read committed" and works. After
> > your change, that simply breaks and gives them an error.
>
> I agree that if we have a user-exposed READ UNCOMMITTED isolation level,
> it shouldn't be just a recovery tool. For a recovery tool, I think a
> set-returning function as part of contrib/pageinspect, for example,
> would be more appropriate. Then it could also try to be more defensive
> against corrupt pages, and be superuser-only.
>

So the consensus is for a more-specifically named facility.

I was aiming for something that would allow general SELECTs to run with a
snapshot that can see uncommitted xacts, so making it a SRF wouldn't really
allow that.

Not really sure where to go with the UI for this.

--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Solutions for the Enterprise