Re: [Proposal] Global temporary tables

pá 24. 1. 2020 v 9:39 odesílatel Konstantin Knizhnik <
k(dot)knizhnik(at)postgrespro(dot)ru> napsal:

>
>
> On 23.01.2020 23:47, Robert Haas wrote:
> > On Sat, Jan 11, 2020 at 8:51 PM Tomas Vondra
> > <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> >> I proposed just ignoring those new indexes because it seems much simpler
> >> than alternative solutions that I can think of, and it's not like those
> >> other solutions don't have other issues.
> > +1.
> >
> >> For example, I've looked at the "on demand" building as implemented in
> >> global_private_temp-8.patch, I kinda doubt adding a bunch of index build
> >> calls into various places in index code seems somewht suspicious.
> > +1. I can't imagine that's a safe or sane thing to do.
> >
>
> As far as you know there are two versions of GTT implementations now.
> And we are going to merge them into single patch.
> But there are some principle question concerning provided functionality
> which has to be be discussed:
> should we prohibit DDL on GTT if there are more than one sessions using
> it. It includes creation/dropping indexes, dropping table, altering
> table...
>
> If the answer is "yes", then the question whether to populate new
> indexes with data is no relevant at all, because such situation will not
> be possible.
> But in this case we will get incompatible behavior with normal
> (permanent) tables and it seems to be very inconvenient from DBA point
> of view:
> it will be necessary to enforce all clients to close their sessions to
> perform some DDL manipulations with GTT.
> Some DDLs will be very difficult to implement if GTT is used by more
> than one backend, for example altering table schema.
>
> My current solution is to allow creation/droping index on GTT and
> dropping table itself, while prohibit alter schema at all for GTT.
> Wenjing's approach is to prohibit any DDL if GTT is used by more than
> one backend.
>

When I create index on GTT in one session, then I don't expect creating
same index in all other sessions that uses same GTT.

But I can imagine to creating index on GTT enforces index in current
session, and for other sessions this index will be invalid to end of
session.

Regards

Pavel

>
> --
> Konstantin Knizhnik
> Postgres Professional: http://www.postgrespro.com
> The Russian Postgres Company
>
>