Re: Use correct collation in pg_trgm

On Fri, Sep 18, 2026 at 8:39 PM David Geier <geidav(dot)pg(at)gmail(dot)com> wrote:
>
> Hi Solai!
>
> > I reviewed the v7 patch series and I tested the changes with a Turkish
> > ICU collation and verified that the collation is now correctly
> > propagated for both trigram lowercasing and word-boundary detection.
> > For the lowercasing changes, show_trgm('ISTANBUL' COLLATE "tr-x-icu")
> > now produces the same trigrams as show_trgm('ıstanbul' COLLATE
> > turkish), and:
> >
> > similarity('ıstanbul' COLLATE turkish,
> > 'ISTANBUL' COLLATE turkish)
> >
> > returns 1, whereas the unpatched behavior produced 0.5.
> >
> > I also tested the word-boundary handling using: helloıtestIworldİcode,
> > with both Turkish ICU and "C" collations. The generated trigrams
> > differ appropriately between the two collations, confirming that the
> > collation is being used while identifying word boundaries. I tested
> > the index paths as well. A GIN trigram index and a GiST trigram index
> > both work correctly for a query using the matching Turkish collation.
> > And also tested an explicitly "C"-collated LIKE query against the
> > Turkish-collated column with sequential scans disabled. The planner
> > did not use the Turkish trigram index and instead showed a disabled
> > sequential scan, which avoids using an index with an incompatible
> > collation. Finally, I ran the complete pg_trgm installcheck suite and
> > all 5 tests passed successfully. I then ran: git diff HEAD~2..HEAD
> > --check, which reported one minor formatting issue:
> > contrib/pg_trgm/sql/pg_trgm_collation.sql:29: new blank line at EOF.
> > This appears to be only a patch formatting issue. I have not modified
> > the contributor's patch for this; I am mentioning it here as a minor
> > review comment.
> > Other than the above minor formatting point, I did not find any
> > functional issues during my testing.
>
> Thanks for the thorough review.
>
> I think with that it's ready for committer.
> Marked accordingly in the commitfest app.
>

Thank you.

Regards
Solai