Re: Index Skip Scan

On Tue, Mar 24, 2020 at 10:08 PM Dmitry Dolgov <9erthalion6(at)gmail(dot)com> wrote:
>
> > On Wed, Mar 11, 2020 at 11:17:51AM +1300, David Rowley wrote:
> >
> > Yes, I was complaining that a ProjectionPath breaks the optimisation
> > and I don't believe there's any reason that it should.
> >
> > I believe the way to make that work correctly requires paying
> > attention to the Path's uniquekeys rather than what type of path it
> > is.
>
> Thanks for the suggestion. As a result of the discussion I've modified
> the patch, does it look similar to what you had in mind?
>
> In this version if all conditions are met and there are corresponding
> unique keys, a new index skip scan path will be added to
> unique_pathlists. In case if requested distinct clauses match with
> unique keys, create_distinct_paths can choose this path without needen
> to know what kind of path is it. Also unique_keys are passed through
> ProjectionPath, so optimization for the example mentioned in this thread
> before now should work (I've added one test for that).
>
> I haven't changed anything about UniqueKey structure itself (one of the
> suggestions was about Expr instead of EquivalenceClass), but I believe
> we need anyway to figure out how two existing imlementation (in this
> patch and from [1]) of this idea can be connected.
>
> [1]: https://www.postgresql.org/message-id/flat/CAKU4AWrwZMAL%3DuaFUDMf4WGOVkEL3ONbatqju9nSXTUucpp_pw%40mail.gmail.com

---
src/backend/nodes/outfuncs.c | 14 ++++++
src/backend/nodes/print.c | 39 +++++++++++++++
src/backend/optimizer/path/Makefile | 3 +-
src/backend/optimizer/path/allpaths.c | 8 +++
src/backend/optimizer/path/indxpath.c | 41 ++++++++++++++++
src/backend/optimizer/path/pathkeys.c | 71 ++++++++++++++++++++++-----
src/backend/optimizer/plan/planagg.c | 1 +
src/backend/optimizer/plan/planmain.c | 1 +
src/backend/optimizer/plan/planner.c | 37 +++++++++++++-
src/backend/optimizer/util/pathnode.c | 46 +++++++++++++----
src/include/nodes/nodes.h | 1 +
src/include/nodes/pathnodes.h | 19 +++++++
src/include/nodes/print.h | 1 +
src/include/optimizer/pathnode.h | 2 +
src/include/optimizer/paths.h | 11 +++++
15 files changed, 272 insertions(+), 23 deletions(-)

Seems like you forgot to add the uniquekey.c file in the
v33-0001-Unique-key.patch.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com