Re: SQL Property Graph Queries (SQL/PGQ)

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.

-- 
Best Wishes,
Ashutosh Bapat