4 files changed, 90 insertions, 5 deletions
diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 3b8d42e4d51..154a8837e17 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -3359,12 +3359,18 @@ jsonb_concat(PG_FUNCTION_ARGS)
 			   *it2;
 
 	/*
-	 * If one of the jsonb is empty, just return other.
+	 * If one of the jsonb is empty, just return the other if it's not
+	 * scalar and both are of the same kind.  If it's a scalar or they are
+	 * of different kinds we need to perform the concatenation even if one is
+	 * empty.
 	 */
-	if (JB_ROOT_COUNT(jb1) == 0)
-		PG_RETURN_JSONB(jb2);
-	else if (JB_ROOT_COUNT(jb2) == 0)
-		PG_RETURN_JSONB(jb1);
+	if (JB_ROOT_IS_OBJECT(jb1) == JB_ROOT_IS_OBJECT(jb2))
+	{
+		if (JB_ROOT_COUNT(jb1) == 0 && !JB_ROOT_IS_SCALAR(jb2))
+			PG_RETURN_JSONB(jb2);
+		else if (JB_ROOT_COUNT(jb2) == 0 && !JB_ROOT_IS_SCALAR(jb1))
+			PG_RETURN_JSONB(jb1);
+	}
 
 	it1 = JsonbIteratorInit(&jb1->root);
 	it2 = JsonbIteratorInit(&jb2->root);
diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index 17656d4413a..82d1b69bfaa 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -2912,6 +2912,42 @@ select '"c"' || '["a", "b"]'::jsonb;
  ["c", "a", "b"]
 (1 row)
 
+select '[]'::jsonb || '["a"]'::jsonb;
+ ?column? 
+----------
+ ["a"]
+(1 row)
+
+select '[]'::jsonb || '"a"'::jsonb;
+ ?column? 
+----------
+ ["a"]
+(1 row)
+
+select '"b"'::jsonb || '"a"'::jsonb;
+  ?column?  
+------------
+ ["b", "a"]
+(1 row)
+
+select '{}'::jsonb || '{"a":"b"}'::jsonb;
+  ?column?  
+------------
+ {"a": "b"}
+(1 row)
+
+select '[]'::jsonb || '{"a":"b"}'::jsonb;
+   ?column?   
+--------------
+ [{"a": "b"}]
+(1 row)
+
+select '{"a":"b"}'::jsonb || '[]'::jsonb;
+   ?column?   
+--------------
+ [{"a": "b"}]
+(1 row)
+
 select '"a"'::jsonb || '{"a":1}';
 ERROR:  invalid concatenation of jsonb objects
 select '{"a":1}' || '"a"'::jsonb;
diff --git a/src/test/regress/expected/jsonb_1.out b/src/test/regress/expected/jsonb_1.out
index 86b1162ac29..2cbc0c79bba 100644
--- a/src/test/regress/expected/jsonb_1.out
+++ b/src/test/regress/expected/jsonb_1.out
@@ -2912,6 +2912,42 @@ select '"c"' || '["a", "b"]'::jsonb;
  ["c", "a", "b"]
 (1 row)
 
+select '[]'::jsonb || '["a"]'::jsonb;
+ ?column? 
+----------
+ ["a"]
+(1 row)
+
+select '[]'::jsonb || '"a"'::jsonb;
+ ?column? 
+----------
+ ["a"]
+(1 row)
+
+select '"b"'::jsonb || '"a"'::jsonb;
+  ?column?  
+------------
+ ["b", "a"]
+(1 row)
+
+select '{}'::jsonb || '{"a":"b"}'::jsonb;
+  ?column?  
+------------
+ {"a": "b"}
+(1 row)
+
+select '[]'::jsonb || '{"a":"b"}'::jsonb;
+   ?column?   
+--------------
+ [{"a": "b"}]
+(1 row)
+
+select '{"a":"b"}'::jsonb || '[]'::jsonb;
+   ?column?   
+--------------
+ [{"a": "b"}]
+(1 row)
+
 select '"a"'::jsonb || '{"a":1}';
 ERROR:  invalid concatenation of jsonb objects
 select '{"a":1}' || '"a"'::jsonb;
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index 83ed4ebd93f..cb03ada1731 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -718,6 +718,13 @@ select '["c"]' || '["a", "b"]'::jsonb;
 select '["a", "b"]'::jsonb || '"c"';
 select '"c"' || '["a", "b"]'::jsonb;
 
+select '[]'::jsonb || '["a"]'::jsonb;
+select '[]'::jsonb || '"a"'::jsonb;
+select '"b"'::jsonb || '"a"'::jsonb;
+select '{}'::jsonb || '{"a":"b"}'::jsonb;
+select '[]'::jsonb || '{"a":"b"}'::jsonb;
+select '{"a":"b"}'::jsonb || '[]'::jsonb;
+
 select '"a"'::jsonb || '{"a":1}';
 select '{"a":1}' || '"a"'::jsonb;