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 611dfce1d6b799d8dad1d4b2d2c6388367790869..d8866373b8f6764d04772bc4cba0cc6dc7635347 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 6c8a18f7b54f92f7062e3812da94182b54fe4856..bc53b2105b493ecab63db4990fc4deb533a1cda7 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;