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/