Re: Bug: Missing collation assignment for GRAPH_TABLE COLUMNS expressions

Hi Ashutosh,

On Wed, Apr 15, 2026 at 8:07 AM Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>
wrote:

> On Fri, Apr 10, 2026 at 11:36 PM SATYANARAYANA NARLAPURAM
> <satyanarlapuram(at)gmail(dot)com> wrote:
> >
> > Hi Ashutosh,
> >
> > On Fri, Apr 10, 2026 at 9:25 AM Ashutosh Bapat <
> ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
> >>
> >> Hi Satya,
> >> Thanks for the report and patch.
> >>
> >> On Fri, Apr 10, 2026 at 9:12 PM SATYANARAYANA NARLAPURAM
> >> <satyanarlapuram(at)gmail(dot)com> wrote:
> >> >
> >> > Hi hackers,
> >> >
> >> > GRAPH_TABLE COLUMNS expressions that involve collation-dependent
> functions or operators fail with:
> >> >
> >> > ERROR: could not determine which collation to use for upper()
> function
> >> > HINT: Use the COLLATE clause to set the collation explicitly.
> >> >
> >> > Setup:
> >> >
> >> > CREATE TABLE vtx (id int PRIMARY KEY, name text);
> >> > CREATE TABLE edg (id int PRIMARY KEY,
> >> > src int REFERENCES vtx(id),
> >> > dst int REFERENCES vtx(id));
> >> > INSERT INTO vtx VALUES (1,'Alice'),(2,'Bob'),(3,'Carol');
> >> > INSERT INTO edg VALUES (1,1,2),(2,2,3);
> >> >
> >> > CREATE PROPERTY GRAPH g
> >> > VERTEX TABLES (vtx KEY (id))
> >> > EDGE TABLES (edg KEY (id)
> >> > SOURCE KEY (src) REFERENCES vtx (id)
> >> > DESTINATION KEY (dst) REFERENCES vtx (id));
> >> >
> >> > postgres=# SELECT * FROM GRAPH_TABLE (g
> >> > MATCH (a IS vtx)-[e IS edg]->(b IS vtx) COLUMNS (upper(a.name) AS
> src_upper));
> >> > ERROR: could not determine which collation to use for upper()
> function
> >> > HINT: Use the COLLATE clause to set the collation explicitly.
> >> >
> >> >
> >> > In transformRangeGraphTable(), the COLUMNS transformation loop calls
> transformExpr()
> >> > on each column expression but omits the subsequent
> assign_expr_collations() call. Both
> >> > WHERE clause transformation sites in parse_graphtable.c correctly
> include it.
> >> >
> >> > Attached a patch to fix this.
> >>
> >> I think the fix is in the right direction. It's better to call
> >> assign_expr_collation only once on all the columns at the end of loop
> >> of rgt->columns, just like assign_expr_collation is called on all the
> >> conditions in WHERE clause once
> >
> >
> > Addressed this in v2 patch.
> >
>
> If we call assign_expr_collations() on a list, the List expression
> also gets a collation, which isn't what we want here. We want to
> assign collations to the individual COLUMNs expression independently.
> assign_list_collations() is better suited for that. I must say that
> your earlier patch had got it right in this regard since it was
> calling assign_expr_collations independently on each COLUMNs
> expression. However, considering that an all properties reference is
> replaced by a list of GraphPropertyRefs in place, I think calling
> assign_list_collations() once on all COLUMNs expressions is a
> future-proof fix. This is also inline with how collations are assigned
> to targetlist expressions in a Query.
>

Nice catch!

>
> >>
> >>
> >>
> >> Good to see tests also included in the patch. Do we need all three
> >> queries? Also those queries should be placed near the section "-- test
> >> collation specified in the expression" and add a query for explicit
> >> collation in COLUMNs expression.
> >
> >
> > Removed two tests and moved the test. Explicit collate test already
> exists.
>
> I merged this test into an existing test to avoid adding yet another
> query in the file that has many many queries already. Yes, an explicit
> collation test is not needed separately.
>

Thanks!

>
> While at it I added comments to explain why we aren't performing
> en-masse collation assignment on a GraphTable or GraphPathPattern.
>
> Please let me know what you think of the attached patch.
>

This LGTM. I reran the tests and all of them are passing.

Thanks,
Satya