Re: Repeatable Read Isolation Level "transaction start time"

On Wed, Sep 25, 2024 at 1:45 PM Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>
wrote:

>
>
> On 9/25/24 10:22 AM, Greg Sabino Mullane wrote:
> > On Tue, Sep 24, 2024 at 10:28 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
> > <mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>> wrote:
> >
> > It's even looser than that, really: it's the first statement that
> > requires an MVCC snapshot.
> >
> >
> > Hm....so why does "SELECT 1;" work as a transaction start marker then,
> > as opposed to "SHOW work_mem;", which does not? Do we simply consider
> > anything with a SELECT as needing a snapshot?
>
>
> SELECT some_func();
>
> Where some_func() does something that requires a snapshot.
>
>
But why does "SELECT 1;" need a snapshot? Heck, why does "SELECT
<immutable>;" need a snapshot?

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