Thread

Re: SQL Property Graph Queries (SQL/PGQ)

Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> — 2025-12-30T11:27:15Z

On Tue, Dec 30, 2025 at 3:14 PM Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
>
> On Thu, Dec 18, 2025 at 2:45 PM Ashutosh Bapat
> <ashutosh.bapat.oss@gmail.com> wrote:
> >
> >
> > >
> > > I did another investigation about whether this level of checking is
> > > necessary.  I think according to the letter of the SQL standard, the
> > > typmods must indeed match.  It seems Oracle does not check (the example
> > > mentioned above came from an Oracle source).  But I think it's okay to
> > > keep the check.  In PostgreSQL, it is much less common to write like
> > > varchar(1000).  And we can always consider relaxing it later.
> >
> > +1.
> >
> > Attached patch adds a couple more test statements.
> >
>
> Squashed this into the main patchset.
>
> > >
> > > 2) I had it in my notes to consider whether we should support the colon
> > > syntax for label expressions.  I think we might have talked about that
> > > before.
> > >
> > > I'm now leaning toward not supporting it in the first iteration.  I
> > > don't know that we have fully explored possible conflicts with host
> > > variable syntax in ecpg and psql and the like.  Maybe avoid that for now.
> > >
> >
> > I was aware of ecpg and I vaguely remember we fixed something in ECPG
> > to allow : in MATCH statement. Probably following changes in
> > psqlscan.l and pgc.l
> > -self                   [,()\[\].;\:\+\-\*\/\%\^\<\>\=]
> > +self                   [,()\[\].;\:\|\+\-\*\/\%\^\<\>\=]
> >
> > Those changes add | after : (and not the : itself) so maybe they are
> > not about supporting : . Do you remember what those are?
>
> I reverted those changes from both the files and ran "meson test". I
> did not observe any failure. It seems those changes are not needed.
> But adding them as a separate commit (0004) in case CI bot reveals any
> failures without them.
>
> I noticed that there were no ECPG tests for SQL/PGQ. Added a basic
> test in patch 0003.
>
> >
> > I spotted some examples that use : in ddl.sgml.
> > <programlisting>
> > SELECT customer_name FROM GRAPH_TABLE (myshop MATCH
> > (c:customer)-[:has]->(o:"order" WHERE o.ordered_when = current_date)
> > COLUMNS (c.name AS customer_name));
> > </programlisting>
> >
> > The query demonstrates that one can use label names in a way that will
> > make the pattern look like an English sentence. Replacing : with IS
> > defeats that purpose.
> >
> > As written in that paragraph, the labels serve the purpose of exposing
> > the table with a different logical view (using different label and
> > property names). So we need that paragraph, but I think we should
> > change the example to use IS instead of :. Attached is suggested
> > minimal change, but I am not happy with it. Another possibility is we
> > completely remove that paragraph; I don't think we need to discuss all
> > possible usages the users will come up with.
> >
> > The patch changes one more instance of : by IS. But that's straight forward.
> >
> > In ddl.sgml I noticed a seemingly incomplete sentence
> >    A property graph is a way to represent database contents, instead of using
> >    relational structures such as tables.
> >
> > Represent the contents as what? I feel the complete sentence should be
> > one of the following
> > property graph is a way to represent database contents as a graph,
> > instead of representing those as relational structures OR
> > property graph is another way to represent database contents instead
> > of using relational structures such as tables
> >
> > But I can't figure out what was originally intended.
>
>
> 0002 contains some edits to this part of documentation. I think the
> paragraph reads better than before. Let me know what you think.
>
> Please let me know which of 0002 to 0004 look good to you. I will
> squash those into the patchset in the next version.

The previous patchset had a whitespace difference in ECPG expected
output files. Fixed in the attached patchset.

-- 
Best Wishes,
Ashutosh Bapat