Subject: pgsql: MERGE ... DO NOTHING: require SELECT privileges

From: Alvaro Herrera <[email-masked]>
Date: Wed, 21 Feb 2024 16:21:25 +0000

MERGE ... DO NOTHING: require SELECT privileges

Verify that a user running MERGE with a DO NOTHING clause has
privileges to read the table, even if no columns are referenced.  Such
privileges were already required if the ON clause or any of the WHEN
conditions referenced any column at all, so there's no functional change
in practice.

This change fixes an assertion failure in the case where no column is
referenced by the command and the WHEN clauses are all DO NOTHING.

Backpatch to 15, where MERGE was introduced.

Reported-by: Alena Rybakina <[email-masked]>
Reported-by: Alexander Lakhin <[email-masked]>
Discussion: https://postgr.es/m/[email-masked]

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/4989ce72644b9d636b9b23c7a1719a405e62670b

Modified Files
--------------
src/backend/parser/parse_merge.c    |  7 ++++++-
src/test/regress/expected/merge.out | 10 ++++++++++
src/test/regress/sql/merge.sql      | 11 +++++++++++
3 files changed, 27 insertions(+), 1 deletion(-)