Re: MERGE output doubt

On 2022-Oct-20, Luca Ferrari wrote:

> Now, if I use  a do nothing merge:
> 
> estdb=> MERGE INTO average_scores a
> USING ( SELECT name, avg( score ) AS avg_score
>        FROM scores GROUP BY name ) s
> ON s.name = a.name
> WHEN MATCHED  THEN
>    do nothing
> WHEN NOT MATCHED THEN
>    do nothing;
> MERGE 2
> 
> I was expecting an output tag like "MERGE 0" since both branches have
> "do nothing", so no tuples should be updated at all on the target
> table.

Hmm, yeah, it should report 0 tuples, according to the documentation.
AFAICS this patch fixes it, will push shortly.

> Moreover, if I truncate the target table and execute again the merge
> query, I got the result of 0:
> 
> testdb=> truncate average_scores ;
> TRUNCATE TABLE
> testdb=> MERGE INTO average_scores a
> USING ( SELECT name, avg( score ) AS avg_score
>        FROM scores GROUP BY name ) s
> ON s.name = a.name
> WHEN MATCHED  THEN   -- caso di match
>    do nothing
> WHEN NOT MATCHED THEN
>    do nothing;
> MERGE 0
> 
> What am I missing here?

Hmm, is this not what you were expecting?  Or are you saying that it
should have been affected by the same bug?

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/