From: Dean Rasheed <dean.a.rasheed@gmail.com>
Date: Tue, 10 Jan 2023 14:16:27 +0000 (+0000)
Subject: Fix MERGE's test for unreachable WHEN clauses.
X-Git-Tag: REL_15_2~41
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=38255f2d0059a101c3fb791d6523a9e66e55aa66;p=thirdparty%2Fpostgresql.git

Fix MERGE's test for unreachable WHEN clauses.

The former code would only detect an unreachable WHEN clause if it had
an AND condition. Fix, so that unreachable unconditional WHEN clauses
are also detected.

Back-patch to v15, where MERGE was added.

Discussion: https://postgr.es/m/CAEZATCVQ=7E2z4cSBB49jjeGGsB6WeoYQY32NDeSvcHiLUZ=ow@mail.gmail.com
---

diff --git a/src/backend/parser/parse_merge.c b/src/backend/parser/parse_merge.c
index 62c2ff69f0c..e8865bfaf54 100644
--- a/src/backend/parser/parse_merge.c
+++ b/src/backend/parser/parse_merge.c
@@ -155,12 +155,12 @@ transformMergeStmt(ParseState *pstate, MergeStmt *stmt)
 		/*
 		 * Check for unreachable WHEN clauses
 		 */
-		if (mergeWhenClause->condition == NULL)
-			is_terminal[when_type] = true;
-		else if (is_terminal[when_type])
+		if (is_terminal[when_type])
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
 					 errmsg("unreachable WHEN clause specified after unconditional WHEN clause")));
+		if (mergeWhenClause->condition == NULL)
+			is_terminal[when_type] = true;
 	}
 
 	/*
diff --git a/src/test/regress/expected/merge.out b/src/test/regress/expected/merge.out
index 958fb85305c..21a82eefbcd 100644
--- a/src/test/regress/expected/merge.out
+++ b/src/test/regress/expected/merge.out
@@ -659,7 +659,7 @@ USING source AS s
 ON t.tid = s.sid
 WHEN MATCHED THEN /* Terminal WHEN clause for MATCHED */
 	DELETE
-WHEN MATCHED AND s.delta > 0 THEN
+WHEN MATCHED THEN
 	UPDATE SET balance = t.balance - s.delta;
 ERROR:  unreachable WHEN clause specified after unconditional WHEN clause
 ROLLBACK;
diff --git a/src/test/regress/sql/merge.sql b/src/test/regress/sql/merge.sql
index 98fe1040bd4..fdbcd708823 100644
--- a/src/test/regress/sql/merge.sql
+++ b/src/test/regress/sql/merge.sql
@@ -438,7 +438,7 @@ USING source AS s
 ON t.tid = s.sid
 WHEN MATCHED THEN /* Terminal WHEN clause for MATCHED */
 	DELETE
-WHEN MATCHED AND s.delta > 0 THEN
+WHEN MATCHED THEN
 	UPDATE SET balance = t.balance - s.delta;
 ROLLBACK;