Feedback-ID: ie0a040ee:Fastmail
Message-ID: <1106ff18-b607-7ff3-e4ab-a3c6e1d46fc7@eisentraut.org>
Date: Mon, 25 Sep 2023 22:00:30 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0)
 Gecko/20100101 Thunderbird/102.15.0
Subject: Re: SQL:2011 application time
To: Paul Jungwirth <pj@illuminatedcomputing.com>,
 jian he <jian.universality@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
References: <CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com>
 <ab4cf49c-9839-3426-5114-f596fa9ee76b@illuminatedcomputing.com>
 <6f010a6e-8e20-658b-dc05-dc9033a694da@eisentraut.org>
 <7d44dade-ff31-5eef-80ac-78ed838066f6@postgresfriends.org>
 <88dadcc1-6652-ff7d-264d-73906a53dee9@illuminatedcomputing.com>
 <CACJufxHD2kv6hCy8yjVk486+d5rcuJS2XxkNH80g9Ui6Rz81Cg@mail.gmail.com>
 <CACJufxFTqiag-4fDPWJLxwwX+2gcZZWJPM9GyhPYD0tH=uM+jQ@mail.gmail.com>
 <CA+renyV4RxkWx57Vi5k_k0d7mkT7+F2kHYuKkwNPBaSOCaotFA@mail.gmail.com>
 <CACJufxG7DKLhyJgBaFttdXZe-4dOVu3NVED+4sdegdGs6R7JdQ@mail.gmail.com>
 <CACJufxFxQH5NxD9UDvbcRCPtaSga+y0+Wwt54PA4KahLwhahOA@mail.gmail.com>
 <5157e85a-6007-27a7-853a-5601d9c3722f@illuminatedcomputing.com>
 <CACJufxGCWDSK2pYMwNdsyDGk6skbP_L5yvSBK67L6pxbGUF8OQ@mail.gmail.com>
 <5a16a59a-d497-7d72-07aa-0afc09d5193a@illuminatedcomputing.com>
 <CACJufxG_iZc8hbdcfjkU6q81kLf4R2Fp=VyDZbyhocuTbMNVEw@mail.gmail.com>
 <b8ef855d-216b-5499-6a6e-ec883a32bd96@illuminatedcomputing.com>
Content-Language: en-US
From: Peter Eisentraut <peter@eisentraut.org>
In-Reply-To: <b8ef855d-216b-5499-6a6e-ec883a32bd96@illuminatedcomputing.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Archived-At: <https://www.postgresql.org/message-id/1106ff18-b607-7ff3-e4ab-a3c6e1d46fc7%40eisentraut.org>
Precedence: bulk

On 25.09.23 21:20, Paul Jungwirth wrote:
> On 9/24/23 21:52, jian he wrote:
>> On Wed, Sep 20, 2023 at 10:50 AM Paul Jungwirth
>> <pj@illuminatedcomputing.com> wrote:
>>>
>>> On 9/17/23 20:11, jian he wrote:
>>>> small issues so far I found, v14.
>>>
>>> Thank you again for the review! v15 is attached.
>>>
>>
>> hi. some tiny issues.
> 
> Rebased v16 patches attached.

Looking through the tests in v16-0001:

+-- PK with no columns just WITHOUT OVERLAPS:
+CREATE TABLE temporal_rng (
+       valid_at tsrange,
+       CONSTRAINT temporal_rng_pk PRIMARY KEY (valid_at WITHOUT OVERLAPS)
+);
+ERROR:  syntax error at or near "WITHOUT"
+LINE 3:  CONSTRAINT temporal_rng_pk PRIMARY KEY (valid_at WITHOUT OV...
+                                                          ^

I think this error is confusing.  The SQL standard requires at least one 
non-period column in a PK.  I don't know why that is or why we should 
implement it.  But if we want to implement it, maybe we should enforce 
that in parse analysis rather than directly in the parser, to be able to 
produce a more friendly error message.

+-- PK with a range column/PERIOD that isn't there:
+CREATE TABLE temporal_rng (
+       id INTEGER,
+       CONSTRAINT temporal_rng_pk PRIMARY KEY (id, valid_at WITHOUT 
OVERLAPS)
+);
+ERROR:  range or PERIOD "valid_at" in WITHOUT OVERLAPS does not exist

I think here we should just produce a "column doesn't exist" error 
message, the same as if the "id" column was invalid.  We don't need to 
get into the details of what kind of column it should be.  That is done 
in the next test

+ERROR:  column "valid_at" in WITHOUT OVERLAPS is not a range type

Also, in any case it would be nice to have a location pointer here (for 
both cases).

+-- PK with one column plus a range:
+CREATE TABLE temporal_rng (
+       -- Since we can't depend on having btree_gist here,
+       -- use an int4range instead of an int.
+       -- (The rangetypes regression test uses the same trick.)
+       id int4range,
+       valid_at tsrange,
+       CONSTRAINT temporal_rng_pk PRIMARY KEY (id, valid_at WITHOUT 
OVERLAPS)
+);

I'm confused why you are using int4range here (and in further tests) for 
the scalar (non-range) part of the primary key.  Wouldn't a plaint int4 
serve here?

+SELECT pg_get_indexdef(conindid, 0, true) FROM pg_constraint WHERE 
conname = 'temporal_rng_pk';
+                                pg_get_indexdef
+-------------------------------------------------------------------------------
+ CREATE UNIQUE INDEX temporal_rng_pk ON temporal_rng USING gist (id, 
valid_at)

Shouldn't this somehow show the operator classes for the columns?  We 
are using different operator classes for the id and valid_at columns, 
aren't we?

+-- PK with USING INDEX (not possible):
+CREATE TABLE temporal3 (
+       id int4range,
+       valid_at tsrange
+);
+CREATE INDEX idx_temporal3_uq ON temporal3 USING gist (id, valid_at);
+ALTER TABLE temporal3
+       ADD CONSTRAINT temporal3_pk
+       PRIMARY KEY USING INDEX idx_temporal3_uq;
+ERROR:  "idx_temporal3_uq" is not a unique index
+LINE 2:  ADD CONSTRAINT temporal3_pk
+             ^
+DETAIL:  Cannot create a primary key or unique constraint using such an 
index.

Could you also add a test where the index is unique and the whole thing 
does work?


Apart from the tests, how about renaming the column 
pg_constraint.contemporal to something like to conwithoutoverlaps?