4 files changed, 25 insertions, 18 deletions
diff --git a/src/backend/catalog/pg_enum.c b/src/backend/catalog/pg_enum.c
index f3161efb20b..bed0f357bb6 100644
--- a/src/backend/catalog/pg_enum.c
+++ b/src/backend/catalog/pg_enum.c
@@ -212,19 +212,30 @@ AddEnumLabel(Oid enumTypeOid,
 	 */
 	LockDatabaseObject(TypeRelationId, enumTypeOid, 0, ExclusiveLock);
 
-	/* Do the "IF NOT EXISTS" test if specified */
-	if (skipIfExists)
+	/*
+	 * Check if label is already in use.  The unique index on pg_enum would
+	 * catch this anyway, but we prefer a friendlier error message, and
+	 * besides we need a check to support IF NOT EXISTS.
+	 */
+	enum_tup = SearchSysCache2(ENUMTYPOIDNAME,
+							   ObjectIdGetDatum(enumTypeOid),
+							   CStringGetDatum(newVal));
+	if (HeapTupleIsValid(enum_tup))
 	{
-		HeapTuple tup;
-
-		tup = SearchSysCache2(ENUMTYPOIDNAME,
-							  ObjectIdGetDatum(enumTypeOid),
-							  CStringGetDatum(newVal));
-		if (HeapTupleIsValid(tup))
+		ReleaseSysCache(enum_tup);
+		if (skipIfExists)
 		{
-			ReleaseSysCache(tup);
+			ereport(NOTICE,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("enum label \"%s\" already exists, skipping",
+							newVal)));
 			return;
 		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_DUPLICATE_OBJECT),
+					 errmsg("enum label \"%s\" already exists",
+							newVal)));
 	}
 
 	pg_enum = heap_open(EnumRelationId, RowExclusiveLock);
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 98fe850c927..214d4f60e32 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2306,7 +2306,7 @@ typedef struct AlterEnumStmt
 	char	   *newVal;			/* new enum value's name */
 	char	   *newValNeighbor; /* neighboring enum value, if specified */
 	bool		newValIsAfter;	/* place new enum value after neighbor? */
-	bool        skipIfExists;   /* ignore statement if label already exists */
+	bool		skipIfExists;	/* no error if label already exists */
 } AlterEnumStmt;
 
 /* ----------------------
diff --git a/src/test/regress/expected/enum.out b/src/test/regress/expected/enum.out
index a14097297a1..ed729dddc3f 100644
--- a/src/test/regress/expected/enum.out
+++ b/src/test/regress/expected/enum.out
@@ -97,11 +97,11 @@ ALTER TYPE planets ADD VALUE 'pluto' AFTER 'zeus';
 ERROR:  "zeus" is not an existing enum label
 -- if not exists tests
 --  existing value gives error
--- We can't do this test because the error contains the
--- offending Oid value, which is unpredictable.
--- ALTER TYPE planets ADD VALUE 'mercury';
+ALTER TYPE planets ADD VALUE 'mercury';
+ERROR:  enum label "mercury" already exists
 -- unless IF NOT EXISTS is specified
 ALTER TYPE planets ADD VALUE IF NOT EXISTS 'mercury';
+NOTICE:  enum label "mercury" already exists, skipping
 -- should be neptune, not mercury
 SELECT enum_last(NULL::planets);
  enum_last 
diff --git a/src/test/regress/sql/enum.sql b/src/test/regress/sql/enum.sql
index db7bf44b408..130a723f698 100644
--- a/src/test/regress/sql/enum.sql
+++ b/src/test/regress/sql/enum.sql
@@ -57,10 +57,7 @@ ALTER TYPE planets ADD VALUE 'pluto' AFTER 'zeus';
 -- if not exists tests
 
 --  existing value gives error
-
--- We can't do this test because the error contains the
--- offending Oid value, which is unpredictable.
--- ALTER TYPE planets ADD VALUE 'mercury';
+ALTER TYPE planets ADD VALUE 'mercury';
 
 -- unless IF NOT EXISTS is specified
 ALTER TYPE planets ADD VALUE IF NOT EXISTS 'mercury';
@@ -73,7 +70,6 @@ ALTER TYPE planets ADD VALUE IF NOT EXISTS 'pluto';
 -- should be pluto, i.e. the new value
 SELECT enum_last(NULL::planets);
 
-
 --
 -- Test inserting so many values that we have to renumber
 --