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

2017-09-12 Thread Tom Lane
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. regards, tom lane diff --git a/src/backend/nodes/outfuncs.c

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

2017-03-19 Thread Jim Nasby
On 3/19/17 2:32 PM, Tom Lane wrote: Jim Nasby writes: Having thought about it, I share Tom's concerns. And now I'm worried about what happens if there are multiple separate OR clauses. I guess those would be handled by separate UNIONs? As proposed, the patch would try

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

2017-03-19 Thread Tom Lane
I wrote: > Consider > SELECT count(*) > FROM a FULL JOIN b ON (a.id = b.id) > WHERE (a.x = 42 OR b.y = 43); > and suppose that a and b have mutual FK constraints guaranteeing that > every non-null a.id value has exactly one match in b and vice versa. Oh, that was sloppy of me.

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

2017-03-19 Thread Tom Lane
Jim Nasby writes: > On 3/16/17 11:54 AM, David Steele wrote: >> On 2/14/17 4:03 PM, Tom Lane wrote: >>> Well, the key point is whether it's really OK to de-dup on the basis >>> of only the CTIDs that are not eliminated in any UNION arm. I was >>> feeling fairly good about

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

2017-03-18 Thread Jim Nasby
On 3/16/17 11:54 AM, David Steele wrote: On 2/14/17 4:03 PM, Tom Lane wrote: Jim Nasby writes: On 2/14/17 1:18 PM, Tom Lane wrote: One point that could use further review is whether the de-duplication algorithm is actually correct. I'm only about 95% convinced by

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

2017-03-16 Thread David Steele
On 2/14/17 4:03 PM, Tom Lane wrote: > Jim Nasby writes: >> On 2/14/17 1:18 PM, Tom Lane wrote: >>> One point that could use further review is whether the de-duplication >>> algorithm is actually correct. I'm only about 95% convinced by the >>> argument I wrote in