Re: Re: BUG #17845: insert into on conflict bug .

On Fri, Mar 17, 2023 at 8:22 AM 德哥 <digoal(at)126(dot)com> wrote:

> In this case, `where a.ts < exclude. ts` and `order by ts desc` are used.
> The ts of the tuple inserted first is the largest. So why throw an error?
> Throwing an error here is obviously not logically correct.
>
> 在 2023-03-16 22:28:27，"jian he" <jian(dot)universality(at)gmail(dot)com> 写道：
>
>
>
> On Thu, Mar 16, 2023 at 5:42 PM PG Bug reporting form <
> noreply(at)postgresql(dot)org> wrote:
>
>> The following bug has been logged on the website:
>>
>> Bug reference: 17845
>> Logged by: Zhou Digoal
>> Email address: digoal(at)126(dot)com
>> PostgreSQL version: 15.2
>> Operating system: macos
>> Description:
>>
>> insert into on conflict bug .
>> In the following insert statement, the row has not been updated multiple
>> times, why is it still showing an error?
>>
>> ```
>> create table a (id int primary key, info text, ts date);
>>
>>
>> insert into a
>> select * from (values (1,'a',date '2022-01-01'),(1,'b',date
>> '2022-01-02'),(1,'c',date '2022-01-03')) as t (id,info,ts) order by ts
>> desc
>> on conflict (id)
>> do update set info=excluded.info, ts=excluded.ts where a.ts <
>> excluded.ts ;
>>
>>
>>
>> QUERY PLAN
>> --------------------------------------------------------------------------
>> Insert on a (cost=0.06..0.10 rows=0 width=0)
>> Conflict Resolution: UPDATE
>> Conflict Arbiter Indexes: a_pkey
>> Conflict Filter: (a.ts < excluded.ts)
>> -> Sort (cost=0.06..0.07 rows=3 width=40)
>> Sort Key: "*VALUES*".column3 DESC
>> -> Values Scan on "*VALUES*" (cost=0.00..0.04 rows=3 width=40)
>> (7 rows)
>>
>>
>> ERROR: 21000: ON CONFLICT DO UPDATE command cannot affect row a second
>> time
>> HINT: Ensure that no rows proposed for insertion within the same command
>> have duplicate constrained values.
>> LOCATION: ExecOnConflictUpdate, nodeModifyTable.c:2054
>> ```
>>
>>
> it's expected behavior.
> See the test expected result in
> src/test/regress/expected/insert_conflict.out, begin with line 694.
>
>
quote from manual:

INSERT with an ON CONFLICT DO UPDATE clause is a “deterministic” statement.
> This means that the command will not be allowed to affect any single
> existing row more than once; a cardinality violation error will be raised
> when this situation arises. Rows proposed for insertion should not
> duplicate each other in terms of attributes constrained by an arbiter index
> or constraint.
>

I think your insertion affects the existing row more than once.