Re: [HACKERS] Custom compression methods

On Wed, Mar 24, 2021 at 3:10 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Wed, Mar 24, 2021 at 2:49 PM Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> >
> > On Wed, Mar 24, 2021 at 02:24:41PM +0530, Dilip Kumar wrote:
> > > On Wed, Mar 24, 2021 at 1:43 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> > > > > create table t1 (col1 text, col2 text);
> > > > > create unique index on t1 ((col1 || col2));
> > > > > insert into t1 values((select array_agg(md5(g::text))::text from
> > > > > generate_series(1, 256) g), version());
> > > > >
> > > > > Attached is a backtrace from current HEAD
> > > >
> > > > Thanks for reporting this issue. Actually, I missed setting the
> > > > attcompression for the expression index and that is causing this
> > > > assert. I will send a patch in some time.
> > >
> > > PFA, patch to fix the issue.
> >
> > Could you include a test case exercizing this code path ?
> > Like Jaime's reproducer.
>
> I will do that.

0001 ->shows compression method for the index attribute in index describe
0002 -> fix the reported bug (test case included)

Apart from this, I was thinking that currently, we are allowing to
ALTER SET COMPRESSION only for the table and matview, IMHO it makes
sense to allow to alter the compression method for the index column as
well? I mean it is just a one-line change, but just wanted to know
the opinion from others. It is not required for the storage because
indexes can not have a toast table but index attributes can be
compressed so it makes sense to allow to alter the compression method.
Thought?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com