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 62c2ff69f0c4d1825fdde5890d673dab13147d10..e8865bfaf543cbc4ffd762d1b682fead46559489 100644 (file)
--- 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 958fb85305c43450596785cd2d5bc24ccce7a40b..21a82eefbcdaa6b27a1a6c5bb0aa3872d2738c5c 100644 (file)
--- 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 98fe1040bd4e91eebbab2812b327e0741a83062c..fdbcd708823100c3ff7c789f0273e107247f0893 100644 (file)
--- 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;