Fix jsonb replace and delete on scalars and empty structures

These operations now error out if attempted on scalars, and simply
return the input if attempted on empty arrays or objects. Along the way
we remove the unnecessary cloning of the input when it's known to be
unchanged. Regression tests covering these cases are added.

1 files changed, 35 insertions, 53 deletions

diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 2d414551276..3dfdbf9d56f 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -3332,7 +3332,7 @@ jsonb_concat(PG_FUNCTION_ARGS)
 		out = JsonbValueToJsonb(res);
 	}
 
-	PG_RETURN_POINTER(out);
+	PG_RETURN_JSONB(out);
 }
 
 
@@ -3349,7 +3349,6 @@ jsonb_delete(PG_FUNCTION_ARGS)
 	text	   *key = PG_GETARG_TEXT_PP(1);
 	char	   *keyptr = VARDATA_ANY(key);
 	int			keylen = VARSIZE_ANY_EXHDR(key);
-	Jsonb	   *out = palloc(VARSIZE(in));
 	JsonbParseState *state = NULL;
 	JsonbIterator *it;
 	uint32		r;
@@ -3357,10 +3356,13 @@ jsonb_delete(PG_FUNCTION_ARGS)
 			   *res = NULL;
 	bool		skipNested = false;
 
-	SET_VARSIZE(out, VARSIZE(in));
+	if (JB_ROOT_IS_SCALAR(in))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("cannot delete from scalar")));
 
 	if (JB_ROOT_COUNT(in) == 0)
-		PG_RETURN_POINTER(out);
+		PG_RETURN_JSONB(in);
 
 	it = JsonbIteratorInit(&in->root);
 
@@ -3382,13 +3384,9 @@ jsonb_delete(PG_FUNCTION_ARGS)
 		res = pushJsonbValue(&state, r, r < WJB_BEGIN_ARRAY ? &v : NULL);
 	}
 
-	if (res == NULL || (res->type == jbvArray && res->val.array.nElems == 0) ||
-		(res->type == jbvObject && res->val.object.nPairs == 0))
-		SET_VARSIZE(out, VARHDRSZ);
-	else
-		out = JsonbValueToJsonb(res);
+	Assert(res != NULL);
 
-	PG_RETURN_POINTER(out);
+	PG_RETURN_JSONB(JsonbValueToJsonb(res));
 }
 
 /*
@@ -3403,7 +3401,6 @@ jsonb_delete_idx(PG_FUNCTION_ARGS)
 {
 	Jsonb	   *in = PG_GETARG_JSONB(0);
 	int			idx = PG_GETARG_INT32(1);
-	Jsonb	   *out = palloc(VARSIZE(in));
 	JsonbParseState *state = NULL;
 	JsonbIterator *it;
 	uint32		r,
@@ -3412,11 +3409,13 @@ jsonb_delete_idx(PG_FUNCTION_ARGS)
 	JsonbValue	v,
 			   *res = NULL;
 
+	if (JB_ROOT_IS_SCALAR(in))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("cannot delete from scalar")));
+
 	if (JB_ROOT_COUNT(in) == 0)
-	{
-		memcpy(out, in, VARSIZE(in));
-		PG_RETURN_POINTER(out);
-	}
+		PG_RETURN_JSONB(in);
 
 	it = JsonbIteratorInit(&in->root);
 
@@ -3435,10 +3434,7 @@ jsonb_delete_idx(PG_FUNCTION_ARGS)
 	}
 
 	if (idx >= n)
-	{
-		memcpy(out, in, VARSIZE(in));
-		PG_RETURN_POINTER(out);
-	}
+		PG_RETURN_JSONB(in);
 
 	pushJsonbValue(&state, r, r < WJB_BEGIN_ARRAY ? &v : NULL);
 
@@ -3457,13 +3453,9 @@ jsonb_delete_idx(PG_FUNCTION_ARGS)
 		res = pushJsonbValue(&state, r, r < WJB_BEGIN_ARRAY ? &v : NULL);
 	}
 
-	if (res == NULL || (res->type == jbvArray && res->val.array.nElems == 0) ||
-		(res->type == jbvObject && res->val.object.nPairs == 0))
-		SET_VARSIZE(out, VARHDRSZ);
-	else
-		out = JsonbValueToJsonb(res);
+	Assert (res != NULL);
 
-	PG_RETURN_POINTER(out);
+	PG_RETURN_JSONB(JsonbValueToJsonb(res));
 }
 
 /*
@@ -3475,7 +3467,6 @@ jsonb_replace(PG_FUNCTION_ARGS)
 	Jsonb	   *in = PG_GETARG_JSONB(0);
 	ArrayType  *path = PG_GETARG_ARRAYTYPE_P(1);
 	Jsonb	   *newval = PG_GETARG_JSONB(2);
-	Jsonb	   *out = palloc(VARSIZE(in) + VARSIZE(newval));
 	JsonbValue *res = NULL;
 	Datum	   *path_elems;
 	bool	   *path_nulls;
@@ -3488,31 +3479,27 @@ jsonb_replace(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
 				 errmsg("wrong number of array subscripts")));
 
+	if (JB_ROOT_IS_SCALAR(in))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("cannot replace path in scalar")));
+
 	if (JB_ROOT_COUNT(in) == 0)
-	{
-		memcpy(out, in, VARSIZE(in));
-		PG_RETURN_POINTER(out);
-	}
+		PG_RETURN_JSONB(in);
 
 	deconstruct_array(path, TEXTOID, -1, false, 'i',
 					  &path_elems, &path_nulls, &path_len);
 
 	if (path_len == 0)
-	{
-		memcpy(out, in, VARSIZE(in));
-		PG_RETURN_POINTER(out);
-	}
+		PG_RETURN_JSONB(in);
 
 	it = JsonbIteratorInit(&in->root);
 
 	res = replacePath(&it, path_elems, path_nulls, path_len, &st, 0, newval);
 
-	if (res == NULL)
-		SET_VARSIZE(out, VARHDRSZ);
-	else
-		out = JsonbValueToJsonb(res);
+	Assert (res != NULL);
 
-	PG_RETURN_POINTER(out);
+	PG_RETURN_JSONB(JsonbValueToJsonb(res));
 }
 
 
@@ -3524,7 +3511,6 @@ jsonb_delete_path(PG_FUNCTION_ARGS)
 {
 	Jsonb	   *in = PG_GETARG_JSONB(0);
 	ArrayType  *path = PG_GETARG_ARRAYTYPE_P(1);
-	Jsonb	   *out = palloc(VARSIZE(in));
 	JsonbValue *res = NULL;
 	Datum	   *path_elems;
 	bool	   *path_nulls;
@@ -3537,31 +3523,27 @@ jsonb_delete_path(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
 				 errmsg("wrong number of array subscripts")));
 
+	if (JB_ROOT_IS_SCALAR(in))
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("cannot delete path in scalar")));
+
 	if (JB_ROOT_COUNT(in) == 0)
-	{
-		memcpy(out, in, VARSIZE(in));
-		PG_RETURN_POINTER(out);
-	}
+		PG_RETURN_JSONB(in);
 
 	deconstruct_array(path, TEXTOID, -1, false, 'i',
 					  &path_elems, &path_nulls, &path_len);
 
 	if (path_len == 0)
-	{
-		memcpy(out, in, VARSIZE(in));
-		PG_RETURN_POINTER(out);
-	}
+		PG_RETURN_JSONB(in);
 
 	it = JsonbIteratorInit(&in->root);
 
 	res = replacePath(&it, path_elems, path_nulls, path_len, &st, 0, NULL);
 
-	if (res == NULL)
-		SET_VARSIZE(out, VARHDRSZ);
-	else
-		out = JsonbValueToJsonb(res);
+	Assert (res != NULL);
 
-	PG_RETURN_POINTER(out);
+	PG_RETURN_JSONB(JsonbValueToJsonb(res));
 }