Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Mon, Mar 18, 2019 at 8:09 AM Noah Misch wrote: > On Tue, Oct 02, 2018 at 10:53:40AM -0400, Tom Lane wrote: > > Noah Misch writes: > > > On Mon, Oct 01, 2018 at 09:32:10PM -0400, Tom Lane wrote: > > >> FWIW, my problem with this patch is that I remain unconvinced of the > basic > > >>

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Tue, Oct 02, 2018 at 10:53:40AM -0400, Tom Lane wrote: > Noah Misch writes: > > On Mon, Oct 01, 2018 at 09:32:10PM -0400, Tom Lane wrote: > >> FWIW, my problem with this patch is that I remain unconvinced of the basic > >> correctness of the transform (specifically the unique-ification

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

Noah Misch writes: > On Mon, Oct 01, 2018 at 09:32:10PM -0400, Tom Lane wrote: >> FWIW, my problem with this patch is that I remain unconvinced of the basic >> correctness of the transform (specifically the unique-ification approach). >> Noah's points would be important to address if we were

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Mon, Oct 01, 2018 at 09:32:10PM -0400, Tom Lane wrote: > Michael Paquier writes: > > On Mon, Sep 03, 2018 at 06:59:10PM -0700, Noah Misch wrote: > >> If you're going to keep this highly-simplified estimate, please expand the > >> comment to say why it doesn't matter or what makes it hard to do

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

Michael Paquier writes: > On Mon, Sep 03, 2018 at 06:59:10PM -0700, Noah Misch wrote: >> If you're going to keep this highly-simplified estimate, please expand the >> comment to say why it doesn't matter or what makes it hard to do better. The >> non-planunionor.c path for the same query

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Mon, Sep 03, 2018 at 06:59:10PM -0700, Noah Misch wrote: > If you're going to keep this highly-simplified estimate, please expand the > comment to say why it doesn't matter or what makes it hard to do better. The > non-planunionor.c path for the same query computes its own estimate of the >

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Sun, Feb 12, 2017 at 09:32:36AM -0800, Tom Lane wrote: > It's not so much poor choices as the cost of the optimization attempt --- > if there's a K-relation OR clause, this will increase the cost of planning > by a factor approaching K+1, whether or not you get a better plan out of > it. I ran

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Thu, Aug 23, 2018 at 5:20 PM, Peter Geoghegan wrote: > This patch adds an enhancement that is an example of a broader class > of optimizer enhancement primarily aimed at making star-schema queries > have more efficient plans, by arranging to use several independent > nested loop joins based on

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Thu, Aug 23, 2018 at 11:10 AM, Tom Lane wrote: > Rebased up to HEAD, per cfbot nagging. Still no substantive change from > v2. I happened to have the opportunity to talk to Tom about this patch in person. I expressed some very general concerns that are worth repeating publicly. This patch

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

I wrote: > [ join-or-to-union-4.patch ] Rebased up to HEAD, per cfbot nagging. Still no substantive change from v2. regards, tom lane diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c index 6269f47..8935503 100644 ***

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On 30 March 2018 at 15:05, Andres Freund wrote: >> + * To allow join removal to happen, we can't reference the CTID column >> + * of an otherwise-removable relation. > > A brief hint why wouldn't hurt. Maybe something like: /* * Join removal is only ever possible when no

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On 3 February 2018 at 03:26, Tom Lane wrote: > Tomas Vondra writes: >> ISTM this patch got somewhat stuck as we're not quite sure the >> transformation is correct in all cases. Is my impression correct? > > Yeah, that's the core issue. > >> If

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

Hi, I've only skimmed the thread, looking at the patch on its own. On 2018-01-04 17:50:48 -0500, Tom Lane wrote: > diff --git a/src/backend/optimizer/plan/plaindex ...dd11e72 . > --- a/src/backend/optimizer/plan/planunionor.c > +++ b/src/backend/optimizer/plan/planunionor.c > @@ -0,0 +1,667 @@

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Fri, Feb 2, 2018 at 4:53 PM, Tom Lane wrote: > Tomas Vondra writes: >> BTW wouldn't it be possible to derive "traditional" proof in relational >> algebra, similarly to other transforms? > > Perhaps. The patch depends on CTID, but you could

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

Tomas Vondra writes: > BTW wouldn't it be possible to derive "traditional" proof in relational > algebra, similarly to other transforms? Perhaps. The patch depends on CTID, but you could probably model that as a primary key in a proof.

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On 02/02/2018 03:26 PM, Tom Lane wrote: > Tomas Vondra writes: >> ISTM this patch got somewhat stuck as we're not quite sure the >> transformation is correct in all cases. Is my impression correct? > > Yeah, that's the core issue. > >> If yes, how to we convince

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

Tomas Vondra writes: > ISTM this patch got somewhat stuck as we're not quite sure the > transformation is correct in all cases. Is my impression correct? Yeah, that's the core issue. > If yes, how to we convince ourselves? Would some sort of automated testing >

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On 01/04/2018 11:50 PM, Tom Lane wrote: > I wrote: >> Jim Nasby writes: >>> I've verified that the patch still applies and make check-world is clean. > >> Not any more :-(. Here's a v3 rebased over HEAD. No substantive >> change from v2. > > Again rebased up to HEAD;

Re: [HACKERS] Re: Improve OR conditions on joined columns (common star schema problem)

On Tue, Sep 12, 2017 at 9:48 PM, Tom Lane wrote: > Jim Nasby writes: >> I've verified that the patch still applies and make check-world is clean. > > Not any more :-(. Here's a v3 rebased over HEAD. No substantive > change from v2. Patch applies and