Re: SQL/JSON json_table plan clause - Mailing list pgsql-hackers

On Thu, 9 Jul 2026 at 21:28, Thom Brown <thom@linux.com> wrote:
>
> On Thu, 9 Jul 2026 at 20:52, Alexander Korotkov <aekorotkov@gmail.com> wrote:
> >
> > Hi, Thom!
> >
> > On Thu, Jul 9, 2026 at 7:12 PM Thom Brown <thom@linux.com> wrote:
> > > On Wed, 8 Jul 2026 at 18:04, Alexander Korotkov <aekorotkov@gmail.com> wrote:
> > > >
> > > > On Wed, Jul 8, 2026 at 6:35 PM Nikita Malakhov <hukutoc@gmail.com> wrote:
> > > > > Alexander, thank you for your participation. I am very sorry, I've seen your previous
> > > > > email but was busy with other tasks and didn't have time to work on your notes.
> > > > > Thank you very much!
> > > >
> > > > OK, no problem.  Are you good with the current shape of the patch?
> > >
> > > I've been giving this a test drive. I saw that this has been
> > > committed, and re-tested against that, and the issues I identified
> > > (unless I've misunderstood some functionality) seem to have survived.
> >
> > I tried my best to check if all the critics is addressed.  SQL/JSON patches
> > go through so many threads.  Sorry that I missed your valuable insights.
>
> You didn't miss anything from me, so nothing to be sorry about. I just
> meant I retested the issues I had found against the commit to see if
> they had been fixed prior to submitting them. I hadn't raised them
> prior to today.
>
> > > First, doesn't this need a catversion bump? This adds fields to
> > > existing node types.
> >
> > Thank you for noticing, catversion is bumped.
> >
> > > I only get the first column from the following. The second one
> > > disappears without error:
> > >
> > > SELECT * FROM JSON_TABLE(
> > >   jsonb '[{"x":[1],"y":[2]}]', '$[*]' AS p0
> > >   COLUMNS (
> > >     NESTED PATH '$.x[*]' AS json_table_path_0 COLUMNS (x int PATH '$'),
> > >     NESTED PATH '$.y[*]' COLUMNS (y int PATH '$')
> > >   )
> > >   PLAN (p0 OUTER json_table_path_0)
> > > ) jt;
> > >  x
> > > ---
> > >  1
> > > (1 row)
> >
> > Yes, there is a bug in assignment of generated names.  Fixed in 0003.
> >
> > > I have the following view:
> > > CREATE VIEW v_chain AS
> > > SELECT * FROM JSON_TABLE(
> > >   jsonb '[{"x": [{"y": [1,2]}]}]', '$[*]' AS p0
> > >   COLUMNS ( NESTED PATH '$.x[*]' AS p1 COLUMNS (
> > >    NESTED PATH '$.y[*]' AS p11 COLUMNS ( y int PATH '$' ) ) )
> > >   PLAN (p0 OUTER (p1 INNER p11))
> > > ) jt;
> > >
> > > When I dump it, I get:
> > >
> > > CREATE VIEW public.v_chain AS
> > >  SELECT y
> > >    FROM JSON_TABLE(
> > >         '[{"x": [{"y": [1, 2]}]}]'::jsonb, '$[*]' AS p0
> > >         COLUMNS (
> > >             NESTED PATH '$."x"[*]' AS p1
> > >             COLUMNS (
> > >                 NESTED PATH '$."y"[*]' AS p11
> > >                 COLUMNS (
> > >                     y integer PATH '$'
> > >                 )
> > >             )
> > >         )
> > >         PLAN (p0 OUTER p1 INNER p11)
> > >     ) jt;
> > >
> > > The parentheses around "p1 INNER p11" aren't preserved.
> >
> > Yes, there is a bug in the deparsing.  0002 fixes that.
> >
> > > Another dump issue with the following:
> > >
> > > CREATE VIEW v_onempty AS SELECT * FROM JSON_TABLE(
> > >   jsonb '{}', '$' AS p0
> > >   COLUMNS ( a int PATH '$.nosuch' ERROR ON EMPTY )
> > >   ERROR ON ERROR
> > > ) jt;
> > >
> > > This dumps as:
> > >
> > > CREATE VIEW public.v_onempty AS
> > >  SELECT a
> > >    FROM JSON_TABLE(
> > >             '{}'::jsonb, '$' AS p0
> > >             COLUMNS (
> > >                 a integer PATH '$."nosuch"'
> > >             ) ERROR ON ERROR
> > >         ) jt;
> > >
> > > It's lost "ERROR ON EMPTY".
> > >
> > >
> > > Another example:
> > >
> > > SELECT * FROM JSON_TABLE(jsonb '"mystring"', '$'
> > >   COLUMNS (a int PATH '$')
> > >   ERROR ON ERROR
> > > ) jt;
> > >
> > > This gives me:
> > >
> > > ERROR:  invalid input syntax for type integer: "mystring"
> > >
> > > But the documentation says that the table-level clause "does not
> > > affect the errors that occur when evaluating columns". Am I missing
> > > something here?
> >
> > I've rechecked with SQL 2023 standard.  AFAICS, ON ERROR clause should
> > be propagated from table to column.  We don't propagate it, so that must be
> > a bug since PG 17.  But this patch shouldn't try to change it, it's out of scope.
> > 0001 reverts attempt to change ON ERROR handling (this also fixes the case
> > about of invalid dumpinged).  I think we need to consider this subject separately.
>
> Yeah, I haven't exercised JSON_TABLE enough since release, so I'm
> clearly late in hitting this.
>
> Thanks for the fixes. I'll try to get round to testing them tomorrow
> unless someone beats me to it.

Attached are some documentation fixes.

Thom