Fix handling of self-modified tuples in MERGE. When an UPDATE or DELETE action in MERGE returns TM_SelfModified, there are 2 possible causes:
1). The target tuple was already updated or deleted by the current command. This can happen if the target row joins to more than one source row, and the SQL standard explicitly says that this must be an error. 2). The target tuple was already updated or deleted by a later command in the current transaction. This can happen if the tuple is modified by a BEFORE trigger or a volatile function used in the query, and should be an error for the same reason that it is in a plain UPDATE or DELETE command. In MERGE's primary error handling block, it failed to check for (2), causing it to return a misleading error message in such cases. In the secondary error handling block, following a concurrent update from another session, it failed to check for (1), causing it to silently ignore target rows joined to more than one source row, instead of reporting an error. Fix this, and add tests for both of these cases. Per report from Wenjiang Zhang. Back-patch to v15, where MERGE was introduced. Discussion: https://postgr.es/m/tencent_41DE0FF443FE14B94A5898D373792109E408%40qq.com Branch ------ REL_16_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/dd73d10adf0048d2d8dc4e94cd64ce5e5ff45a4b Modified Files -------------- src/backend/executor/nodeModifyTable.c | 46 +++++++++++++++++++++++----- src/test/isolation/expected/merge-update.out | 43 ++++++++++++++++++++++++++ src/test/isolation/specs/merge-update.spec | 13 ++++++++ src/test/regress/expected/triggers.out | 8 +++++ src/test/regress/sql/triggers.sql | 4 +++ 5 files changed, 106 insertions(+), 8 deletions(-)