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/
>From 4282eadc0af3061dc53a5bc1ffcdd51b03cc28c4 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@xxxxxxxxxxxxxx>
Date: Thu, 17 Nov 2022 11:58:42 +0100
Subject: [PATCH] fix MERGE tuple count with DO NOTHING
---
src/backend/executor/nodeModifyTable.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index d8fd3cfdbe..fe2b8e4bac 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -2805,7 +2805,7 @@ lmerge_matched:
{
case TM_Ok:
/* all good; perform final actions */
- if (canSetTag)
+ if (canSetTag && commandType != CMD_NOTHING)
(estate->es_processed)++;
break;
--
2.30.2
