Horton

Re: Schema variables - new implementation for Postgres 15

Dmitry Dolgov <9erthalion6@gmail.com>

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From: Dmitry Dolgov <9erthalion6@gmail.com>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Julien Rouhaud <rjuju123@gmail.com>, dean.a.rasheed@gmail.com, er@xs4all.nl, joel@compiler.org, pgsql-hackers@lists.postgresql.org
Date: 2022-11-04T14:28:42Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Allow underscores in integer and numeric constants.

  2. Remove special outfuncs/readfuncs handling of RangeVar.catalogname.

  3. Remove extra space from dumped ALTER DEFAULT PRIVILEGES.

  4. Create FKs properly when attaching table as partition

  5. psql: improve tab-complete's handling of variant SQL names.

> On Fri, Nov 04, 2022 at 03:17:18PM +0100, Pavel Stehule wrote:
> > I've stumbled upon something that looks weird to me (inspired by the
> > example from tests):
> >
> >     =# create variable v2 as int;
> >     =# let v2 = 3;
> >     =# create view vv2 as select coalesce(v2, 0) + 1000 as result
> >
> >     =# select * from vv2;
> >      result
> >      --------
> >         1003
> >
> >     =# set force_parallel_mode to on;
> >     =# select * from vv2;
> >      result
> >      --------
> >         1000
> >
> > In the second select the actual work is done from a worker backend.
> > Since values of session variables are stored in the backend local
> > memory, it's not being shared with the worker and the value is not found
> > in the hash map. Does this suppose to be like that?
> >
>
> It looks like a bug, but parallel queries should be supported.
>
> The value of the variable is passed as parameter to the worker backend. But
> probably somewhere the original reference was not replaced by parameter
>
> On Fri, Nov 04, 2022 at 10:17:13PM +0800, Julien Rouhaud wrote:
> Hi,
>
> There's code to serialize and restore all used variables for parallel workers
> (see code about PARAM_VARIABLE and queryDesc->num_session_variables /
> queryDesc->plannedstmt->sessionVariables).  I haven't reviewed that part yet,
> but it's supposed to be working.  Blind guess would be that it's missing
> something in expression walker.

I see, thanks. I'll take a deeper look, my initial assumption was due to
the fact that in the worker case create_sessionvars_hashtables is
getting called for every query.