Re: WIP: BRIN multi-range indexes

On Fri, 3 Jul 2020 at 09:58, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>
> On Sun, Apr 05, 2020 at 08:01:50PM +0300, Alexander Korotkov wrote:
> >On Sun, Apr 5, 2020 at 8:00 PM Tomas Vondra
> ><tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> ...
> >> >
> >> >Assuming we're not going to get 0001-0003 into v13, I'm not so
> >> >inclined to rush on these three as well. But you're willing to commit
> >> >them, you can count round of review on me.
> >> >
> >>
> >> I have no intention to get 0001-0003 committed. I think those changes
> >> are beneficial on their own, but the primary reason was to support the
> >> new opclasses (which require those changes). And those parts are not
> >> going to make it into v13 ...
> >
> >OK, no problem.
> >Let's do this for v14.
> >
>
> Hi Alexander,
>
> Are you still interested in reviewing those patches? I'll take a look at
> 0001-0003 to check that your previous feedback was addressed. Do you
> have any comments about 0004 / 0005, which I think are the more
> interesting parts of this series?
>
>
> Attached is a rebased version - I realized I forgot to include 0005 in
> the last update, for some reason.
>

I've done a quick test with this patch set. I wonder if we can improve
brin_page_items() SQL function in pageinspect as well. Currently,
brin_page_items() is hard-coded to support only normal brin indexes.
When we pass brin-bloom or brin-multi-range to that function the
binary values are shown in 'value' column but it seems not helpful for
users. For instance, here is an output of brin_page_items() with a
brin-multi-range index:

postgres(1:12801)=# select * from brin_page_items(get_raw_page('mul',
2), 'mul');
-[ RECORD 1 ]----------------------------------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------------------------------------------
----------------------------
itemoffset | 1
blknum | 0
attnum | 1
allnulls | f
hasnulls | f
placeholder | f
value | {\x010000001b0000002000000001000000e5700000e6700000e7700000e8700000e9700000ea700000eb700000ec700000ed700000ee700000ef
700000f0700000f1700000f2700000f3700000f4700000f5700000f6700000f7700000f8700000f9700000fa700000fb700000fc700000fd700000fe700000ff700
00000710000}

Also, I got an assertion failure when setting false_positive_rate reloption:

postgres(1:12448)=# create index blm on t using brin (c int4_bloom_ops
(false_positive_rate = 1));
TRAP: FailedAssertion("(false_positive_rate > 0) &&
(false_positive_rate < 1.0)", File: "brin_bloom.c", Line: 300)

I'll look at the code in depth and let you know if I find a problem.

Regards,

--
Masahiko Sawada http://www.2ndQuadrant.com/

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