Throw error when assigning jsonb scalar instead of a composite object

During the jsonb subscripting assignment, the provided path might assume an
object or an array where the source jsonb has a scalar value.  Initial
subscripting assignment logic will skip such an update operation with no
message shown.  This commit makes it throw an error to indicate this type
of situation.

Discussion: https://postgr.es/m/CA%2Bq6zcV8qvGcDXurwwgUbwACV86Th7G80pnubg42e-p9gsSf%3Dg%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcX3mdxGCgdThzuySwH-ApyHHM-G4oB1R0fn0j2hZqqkLQ%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVDuGBv%3DM0FqBYX8DPebS3F_0KQ6OVFobGJPM507_SZ_w%40mail.gmail.com
Discussion: https://postgr.es/m/CA%2Bq6zcVovR%2BXY4mfk-7oNk-rF91gH0PebnNfuUjuuDsyHjOcVA%40mail.gmail.com
Author: Dmitry Dolgov
Reviewed-by: Tom Lane, Arthur Zakirov, Pavel Stehule, Dian M Fay
Reviewed-by: Andrew Dunstan, Chapman Flack, Merlin Moncure, Peter Geoghegan
Reviewed-by: Alvaro Herrera, Jim Nasby, Josh Berkus, Victor Wagner
Reviewed-by: Aleksander Alekseev, Robert Haas, Oleg Bartunov

3 files changed, 73 insertions, 0 deletions

diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index a0e1266e571..215a10f16ef 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -4931,6 +4931,21 @@ setPath(JsonbIterator **it, Datum *path_elems,
 	switch (r)
 	{
 		case WJB_BEGIN_ARRAY:
+
+			/*
+			 * If instructed complain about attempts to replace whithin a raw
+			 * scalar value. This happens even when current level is equal to
+			 * path_len, because the last path key should also correspond to
+			 * an object or an array, not raw scalar.
+			 */
+			if ((op_type & JB_PATH_FILL_GAPS) && (level <= path_len - 1) &&
+				v.val.array.rawScalar)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("cannot replace existing key"),
+						 errdetail("The path assumes key is a composite object, "
+								   "but it is a scalar value.")));
+
 			(void) pushJsonbValue(st, r, NULL);
 			setPathArray(it, path_elems, path_nulls, path_len, st, level,
 						 newval, v.val.array.nElems, op_type);
@@ -4948,6 +4963,20 @@ setPath(JsonbIterator **it, Datum *path_elems,
 			break;
 		case WJB_ELEM:
 		case WJB_VALUE:
+
+			/*
+			 * If instructed complain about attempts to replace whithin a
+			 * scalar value. This happens even when current level is equal to
+			 * path_len, because the last path key should also correspond to
+			 * an object or an array, not an element or value.
+			 */
+			if ((op_type & JB_PATH_FILL_GAPS) && (level <= path_len - 1))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("cannot replace existing key"),
+						 errdetail("The path assumes key is a composite object, "
+								   "but it is a scalar value.")));
+
 			res = pushJsonbValue(st, r, &v);
 			break;
 		default:
diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index 5b5510c4fdc..cf0ce0e44cc 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -5134,6 +5134,33 @@ select * from test_jsonb_subscript;
   1 | {"a": [null, {"c": [null, null, 1]}]}
 (1 row)
 
+-- trying replace assuming a composite object, but it's an element or a value
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"a": 1}');
+update test_jsonb_subscript set test_json['a']['b'] = '1';
+ERROR:  cannot replace existing key
+DETAIL:  The path assumes key is a composite object, but it is a scalar value.
+update test_jsonb_subscript set test_json['a']['b']['c'] = '1';
+ERROR:  cannot replace existing key
+DETAIL:  The path assumes key is a composite object, but it is a scalar value.
+update test_jsonb_subscript set test_json['a'][0] = '1';
+ERROR:  cannot replace existing key
+DETAIL:  The path assumes key is a composite object, but it is a scalar value.
+update test_jsonb_subscript set test_json['a'][0]['c'] = '1';
+ERROR:  cannot replace existing key
+DETAIL:  The path assumes key is a composite object, but it is a scalar value.
+update test_jsonb_subscript set test_json['a'][0][0] = '1';
+ERROR:  cannot replace existing key
+DETAIL:  The path assumes key is a composite object, but it is a scalar value.
+-- trying replace assuming a composite object, but it's a raw scalar
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, 'null');
+update test_jsonb_subscript set test_json[0] = '1';
+ERROR:  cannot replace existing key
+DETAIL:  The path assumes key is a composite object, but it is a scalar value.
+update test_jsonb_subscript set test_json[0][0] = '1';
+ERROR:  cannot replace existing key
+DETAIL:  The path assumes key is a composite object, but it is a scalar value.
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);
                                 to_tsvector                                
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index 0320db0ea46..1a9d21741fa 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -1371,6 +1371,23 @@ insert into test_jsonb_subscript values (1, '{"a": []}');
 update test_jsonb_subscript set test_json['a'][1]['c'][2] = '1';
 select * from test_jsonb_subscript;
 
+-- trying replace assuming a composite object, but it's an element or a value
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '{"a": 1}');
+update test_jsonb_subscript set test_json['a']['b'] = '1';
+update test_jsonb_subscript set test_json['a']['b']['c'] = '1';
+update test_jsonb_subscript set test_json['a'][0] = '1';
+update test_jsonb_subscript set test_json['a'][0]['c'] = '1';
+update test_jsonb_subscript set test_json['a'][0][0] = '1';
+
+-- trying replace assuming a composite object, but it's a raw scalar
+
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, 'null');
+update test_jsonb_subscript set test_json[0] = '1';
+update test_jsonb_subscript set test_json[0][0] = '1';
+
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);