Fix corner-case behaviors in JSON/JSONB field extraction operators.

Cause the path extraction operators to return their lefthand input,
not NULL, if the path array has no elements.  This seems more consistent
since the case ought to correspond to applying the simple extraction
operator (->) zero times.

Cause other corner cases in field/element/path extraction to return NULL
rather than failing.  This behavior is arguably more useful than throwing
an error, since it allows an expression index using these operators to be
built even when not all values in the column are suitable for the
extraction being indexed.  Moreover, we already had multiple
inconsistencies between the path extraction operators and the simple
extraction operators, as well as inconsistencies between the JSON and
JSONB code paths.  Adopt a uniform rule of returning NULL rather than
throwing an error when the JSON input does not have a structure that
permits the request to be satisfied.

Back-patch to 9.4.  Update the release notes to list this as a behavior
change since 9.3.

doc/src/sgml/func.sgml

@@ -10152,10 +10152,14 @@ table2-mapping
   <note>
    <para>
     There are parallel variants of these operators for both the
-    <type>json</type> and <type>jsonb</type> types.  The operators
+    <type>json</type> and <type>jsonb</type> types.
+    The field/element/path extraction operators
     return the same type as their left-hand input (either <type>json</type>
     or <type>jsonb</type>), except for those specified as
     returning <type>text</>, which coerce the value to text.
+    The field/element/path extraction operators return NULL, rather than
+    failing, if the JSON input does not have the right structure to match
+    the request; for example if no such element exists.
    </para>
   </note>
   <para>

doc/src/sgml/json.sgml

@@ -415,9 +415,6 @@ SELECT jdoc->'guid', jdoc->'name' FROM api WHERE jdoc -> 'tags' ? 'qui'
     the <literal>"tags"</> key is common, defining an index like this
     may be worthwhile:
 <programlisting>
--- Note that the "jsonb -&gt; text" operator can only be called on a JSON
--- object, so as a consequence of creating this index the root of each
--- "jdoc" value must be an object.  This is enforced during insertion.
 CREATE INDEX idxgintags ON api USING gin ((jdoc -&gt; 'tags'));
 </programlisting>
     Now, the <literal>WHERE</> clause <literal>jdoc -&gt; 'tags' ? 'qui'</>

doc/src/sgml/release-9.4.sgml

@@ -136,6 +136,39 @@
      </para>
     </listitem>
 
+    <listitem>
+     <para>
+      The <link linkend="functions-json-op-table"><type>json</type>
+      <literal>#&gt;</> <type>text[]</> path extraction operator</link> now
+      returns its lefthand input, not NULL, if the array is empty (Tom Lane)
+     </para>
+
+     <para>
+      This is consistent with the notion that this represents zero
+      applications of the simple field/element extraction
+      operator <literal>-&gt;</>.  Similarly, <type>json</type>
+      <literal>#&gt;&gt;</> <type>text[]</> with an empty array merely
+      coerces its lefthand input to text.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      Corner cases in
+      the <link linkend="functions-json-op-table"><type>JSON</type>
+      field/element/path extraction operators</link> now return NULL rather
+      than raising an error (Tom Lane)
+     </para>
+
+     <para>
+      For example, applying field extraction to a JSON array now yields NULL
+      not an error.  This is more consistent (since some comparable cases such
+      as no-such-field already returned NULL), and it makes it safe to create
+      expression indexes that use these operators, since they will now not
+      throw errors for any valid JSON input.
+     </para>
+    </listitem>
+
     <listitem>
      <para>
       Cause consecutive whitespace in <link

src/test/regress/expected/json.out

@@ -506,11 +506,19 @@ INSERT INTO test_json VALUES
 SELECT test_json -> 'x'
 FROM test_json
 WHERE json_type = 'scalar';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x'
 FROM test_json
 WHERE json_type = 'array';
-ERROR:  cannot extract field from a non-object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x'
 FROM test_json
 WHERE json_type = 'object';
@@ -538,7 +546,11 @@ WHERE json_type = 'object';
 SELECT test_json -> 2
 FROM test_json
 WHERE json_type = 'scalar';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 2
 FROM test_json
 WHERE json_type = 'array';
@@ -550,7 +562,11 @@ WHERE json_type = 'array';
 SELECT test_json -> 2
 FROM test_json
 WHERE json_type = 'object';
-ERROR:  cannot extract array element from a non-array
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json->>2
 FROM test_json
 WHERE json_type = 'array';
@@ -667,7 +683,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> 1;
-ERROR:  cannot extract array element from a non-array
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> 'z';
  ?column? 
 ----------
@@ -693,11 +713,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::json -> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::json -> 'z';
-ERROR:  cannot extract field from a non-object
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::json -> 'b';
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::json -> 1;
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json -> 'z';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> null::text;
  ?column? 
 ----------
@@ -711,7 +749,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> 1;
-ERROR:  cannot extract array element from a non-array
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> 'z';
  ?column? 
 ----------
@@ -737,11 +779,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::json ->> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::json ->> 'z';
-ERROR:  cannot extract field from a non-object
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::json ->> 'b';
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json ->> 1;
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json ->> 'z';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 -- array length
 SELECT json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]');
  json_array_length 
@@ -922,9 +982,33 @@ select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>array['f2','1'];
 
 -- corner cases for same
 select '{"a": {"b":{"c": "foo"}}}'::json #> '{}';
+         ?column?          
+---------------------------
+ {"a": {"b":{"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::json #> '{}';
  ?column? 
 ----------
- 
+ [1,2,3]
+(1 row)
+
+select '"foo"'::json #> '{}';
+ ?column? 
+----------
+ "foo"
+(1 row)
+
+select '42'::json #> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::json #> '{}';
+ ?column? 
+----------
+ null
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a'];
@@ -934,9 +1018,17 @@ select '{"a": {"b":{"c": "foo"}}}'::json #> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a', null];
-ERROR:  cannot call json_extract_path with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a', ''];
-ERROR:  cannot call json_extract_path with empty path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a','b'];
    ?column?   
 --------------
@@ -985,6 +1077,12 @@ select '[{"b": "c"}, {"b": "cc"}]'::json #> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::json #> array['1','b'];
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::json #> array['z'];
  ?column? 
 ----------
@@ -1004,6 +1102,30 @@ select '42'::json #> array['0'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #>> '{}';
+         ?column?          
+---------------------------
+ {"a": {"b":{"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::json #>> '{}';
+ ?column? 
+----------
+ [1,2,3]
+(1 row)
+
+select '"foo"'::json #>> '{}';
+ ?column? 
+----------
+ foo
+(1 row)
+
+select '42'::json #>> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::json #>> '{}';
  ?column? 
 ----------
  
@@ -1016,9 +1138,17 @@ select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a', null];
-ERROR:  cannot call json_extract_path_text with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a', ''];
-ERROR:  cannot call json_extract_path_text with empty path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a','b'];
    ?column?   
 --------------
@@ -1067,6 +1197,12 @@ select '[{"b": "c"}, {"b": "cc"}]'::json #>> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::json #>> array['1','b'];
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json #>> array['z'];
  ?column? 
 ----------

src/test/regress/expected/json_1.out

@@ -506,11 +506,19 @@ INSERT INTO test_json VALUES
 SELECT test_json -> 'x'
 FROM test_json
 WHERE json_type = 'scalar';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x'
 FROM test_json
 WHERE json_type = 'array';
-ERROR:  cannot extract field from a non-object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x'
 FROM test_json
 WHERE json_type = 'object';
@@ -538,7 +546,11 @@ WHERE json_type = 'object';
 SELECT test_json -> 2
 FROM test_json
 WHERE json_type = 'scalar';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 2
 FROM test_json
 WHERE json_type = 'array';
@@ -550,7 +562,11 @@ WHERE json_type = 'array';
 SELECT test_json -> 2
 FROM test_json
 WHERE json_type = 'object';
-ERROR:  cannot extract array element from a non-array
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json->>2
 FROM test_json
 WHERE json_type = 'array';
@@ -667,7 +683,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> 1;
-ERROR:  cannot extract array element from a non-array
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> 'z';
  ?column? 
 ----------
@@ -693,11 +713,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::json -> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::json -> 'z';
-ERROR:  cannot extract field from a non-object
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::json -> 'b';
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::json -> 1;
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json -> 'z';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> null::text;
  ?column? 
 ----------
@@ -711,7 +749,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> 1;
-ERROR:  cannot extract array element from a non-array
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> 'z';
  ?column? 
 ----------
@@ -737,11 +779,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::json ->> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::json ->> 'z';
-ERROR:  cannot extract field from a non-object
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::json ->> 'b';
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json ->> 1;
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json ->> 'z';
-ERROR:  cannot extract element from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 -- array length
 SELECT json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]');
  json_array_length 
@@ -922,9 +982,33 @@ select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>array['f2','1'];
 
 -- corner cases for same
 select '{"a": {"b":{"c": "foo"}}}'::json #> '{}';
+         ?column?          
+---------------------------
+ {"a": {"b":{"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::json #> '{}';
  ?column? 
 ----------
- 
+ [1,2,3]
+(1 row)
+
+select '"foo"'::json #> '{}';
+ ?column? 
+----------
+ "foo"
+(1 row)
+
+select '42'::json #> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::json #> '{}';
+ ?column? 
+----------
+ null
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a'];
@@ -934,9 +1018,17 @@ select '{"a": {"b":{"c": "foo"}}}'::json #> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a', null];
-ERROR:  cannot call json_extract_path with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a', ''];
-ERROR:  cannot call json_extract_path with empty path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a','b'];
    ?column?   
 --------------
@@ -985,6 +1077,12 @@ select '[{"b": "c"}, {"b": "cc"}]'::json #> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::json #> array['1','b'];
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::json #> array['z'];
  ?column? 
 ----------
@@ -1004,6 +1102,30 @@ select '42'::json #> array['0'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #>> '{}';
+         ?column?          
+---------------------------
+ {"a": {"b":{"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::json #>> '{}';
+ ?column? 
+----------
+ [1,2,3]
+(1 row)
+
+select '"foo"'::json #>> '{}';
+ ?column? 
+----------
+ foo
+(1 row)
+
+select '42'::json #>> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::json #>> '{}';
  ?column? 
 ----------
  
@@ -1016,9 +1138,17 @@ select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a', null];
-ERROR:  cannot call json_extract_path_text with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a', ''];
-ERROR:  cannot call json_extract_path_text with empty path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a','b'];
    ?column?   
 --------------
@@ -1067,6 +1197,12 @@ select '[{"b": "c"}, {"b": "cc"}]'::json #>> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::json #>> array['1','b'];
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::json #>> array['z'];
  ?column? 
 ----------

src/test/regress/expected/jsonb.out

@@ -311,9 +311,17 @@ INSERT INTO test_jsonb VALUES
 ('array','["zero", "one","two",null,"four","five", [1,2,3],{"f1":9}]'),
 ('object','{"field1":"val1","field2":"val2","field3":null, "field4": 4, "field5": [1,2,3], "field6": {"f1":9}}');
 SELECT test_json -> 'x' FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x' FROM test_jsonb WHERE json_type = 'array';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x' FROM test_jsonb WHERE json_type = 'object';
  ?column? 
 ----------
@@ -327,9 +335,17 @@ SELECT test_json -> 'field2' FROM test_jsonb WHERE json_type = 'object';
 (1 row)
 
 SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'array';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'object';
  ?column? 
 ----------
@@ -337,7 +353,11 @@ SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'object';
 (1 row)
 
 SELECT test_json -> 2 FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 2 FROM test_jsonb WHERE json_type = 'array';
  ?column? 
 ----------
@@ -351,7 +371,11 @@ SELECT test_json -> 9 FROM test_jsonb WHERE json_type = 'array';
 (1 row)
 
 SELECT test_json -> 2 FROM test_jsonb WHERE json_type = 'object';
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 6 FROM test_jsonb WHERE json_type = 'array';
  ?column?  
 -----------
@@ -383,7 +407,11 @@ SELECT test_json ->> 'field6' FROM test_jsonb WHERE json_type = 'object';
 (1 row)
 
 SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_array_element_text on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'array';
  ?column? 
 ----------
@@ -391,7 +419,11 @@ SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'array';
 (1 row)
 
 SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'object';
-ERROR:  cannot call jsonb_array_element_text on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT jsonb_object_keys(test_json) FROM test_jsonb WHERE json_type = 'scalar';
 ERROR:  cannot call jsonb_object_keys on a scalar
 SELECT jsonb_object_keys(test_json) FROM test_jsonb WHERE json_type = 'array';
@@ -446,7 +478,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb -> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb -> 1;
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb -> 'z';
  ?column? 
 ----------
@@ -472,11 +508,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 'z';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::jsonb -> 'b';
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::jsonb -> 1;
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb -> 'z';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> null::text;
  ?column? 
 ----------
@@ -490,7 +544,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> 1;
-ERROR:  cannot call jsonb_array_element_text on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> 'z';
  ?column? 
 ----------
@@ -516,11 +574,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb ->> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb ->> 'z';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::jsonb ->> 'b';
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb ->> 1;
-ERROR:  cannot call jsonb_array_element_text on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb ->> 'z';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 -- equality and inequality
 SELECT '{"x":"y"}'::jsonb = '{"x":"y"}'::jsonb;
  ?column? 
@@ -1269,9 +1345,33 @@ SELECT '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::jsonb#>>array['f2','1'];
 
 -- corner cases for same
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> '{}';
+          ?column?          
+----------------------------
+ {"a": {"b": {"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::jsonb #> '{}';
+ ?column?  
+-----------
+ [1, 2, 3]
+(1 row)
+
+select '"foo"'::jsonb #> '{}';
  ?column? 
 ----------
- 
+ "foo"
+(1 row)
+
+select '42'::jsonb #> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::jsonb #> '{}';
+ ?column? 
+----------
+ null
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a'];
@@ -1281,7 +1381,11 @@ select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a', null];
-ERROR:  cannot call jsonb_extract_path with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a', ''];
  ?column? 
 ----------
@@ -1336,13 +1440,55 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb #> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::jsonb #> array['1','b'];
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::jsonb #> array['z'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #> array['f2'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #> array['0'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> '{}';
+          ?column?          
+----------------------------
+ {"a": {"b": {"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::jsonb #>> '{}';
+ ?column?  
+-----------
+ [1, 2, 3]
+(1 row)
+
+select '"foo"'::jsonb #>> '{}';
+ ?column? 
+----------
+ foo
+(1 row)
+
+select '42'::jsonb #>> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::jsonb #>> '{}';
  ?column? 
 ----------
  
@@ -1355,7 +1501,11 @@ select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a', null];
-ERROR:  cannot call jsonb_extract_path_text with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a', ''];
  ?column? 
 ----------
@@ -1410,12 +1560,30 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb #>> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::jsonb #>> array['1','b'];
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb #>> array['z'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #>> array['f2'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #>> array['0'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 -- array_elements
 SELECT jsonb_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]');
     jsonb_array_elements    
@@ -2105,7 +2273,11 @@ SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb -> 'e';
 (1 row)
 
 SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb -> 0; --expecting error
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT '["a","b","c",[1,2],null]'::jsonb -> 0;
  ?column? 
 ----------

src/test/regress/expected/jsonb_1.out

@@ -311,9 +311,17 @@ INSERT INTO test_jsonb VALUES
 ('array','["zero", "one","two",null,"four","five", [1,2,3],{"f1":9}]'),
 ('object','{"field1":"val1","field2":"val2","field3":null, "field4": 4, "field5": [1,2,3], "field6": {"f1":9}}');
 SELECT test_json -> 'x' FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x' FROM test_jsonb WHERE json_type = 'array';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 'x' FROM test_jsonb WHERE json_type = 'object';
  ?column? 
 ----------
@@ -327,9 +335,17 @@ SELECT test_json -> 'field2' FROM test_jsonb WHERE json_type = 'object';
 (1 row)
 
 SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'array';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'object';
  ?column? 
 ----------
@@ -337,7 +353,11 @@ SELECT test_json ->> 'field2' FROM test_jsonb WHERE json_type = 'object';
 (1 row)
 
 SELECT test_json -> 2 FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json -> 2 FROM test_jsonb WHERE json_type = 'array';
  ?column? 
 ----------
@@ -351,7 +371,11 @@ SELECT test_json -> 9 FROM test_jsonb WHERE json_type = 'array';
 (1 row)
 
 SELECT test_json -> 2 FROM test_jsonb WHERE json_type = 'object';
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 6 FROM test_jsonb WHERE json_type = 'array';
  ?column?  
 -----------
@@ -383,7 +407,11 @@ SELECT test_json ->> 'field6' FROM test_jsonb WHERE json_type = 'object';
 (1 row)
 
 SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'scalar';
-ERROR:  cannot call jsonb_array_element_text on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'array';
  ?column? 
 ----------
@@ -391,7 +419,11 @@ SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'array';
 (1 row)
 
 SELECT test_json ->> 2 FROM test_jsonb WHERE json_type = 'object';
-ERROR:  cannot call jsonb_array_element_text on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT jsonb_object_keys(test_json) FROM test_jsonb WHERE json_type = 'scalar';
 ERROR:  cannot call jsonb_object_keys on a scalar
 SELECT jsonb_object_keys(test_json) FROM test_jsonb WHERE json_type = 'array';
@@ -446,7 +478,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb -> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb -> 1;
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb -> 'z';
  ?column? 
 ----------
@@ -472,11 +508,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 'z';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::jsonb -> 'b';
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::jsonb -> 1;
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb -> 'z';
-ERROR:  cannot call jsonb_object_field (jsonb -> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> null::text;
  ?column? 
 ----------
@@ -490,7 +544,11 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> null::int;
 (1 row)
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> 1;
-ERROR:  cannot call jsonb_array_element_text on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> 'z';
  ?column? 
 ----------
@@ -516,11 +574,29 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb ->> 3;
 (1 row)
 
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb ->> 'z';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on an array
+ ?column? 
+----------
+ 
+(1 row)
+
+select '{"a": "c", "b": null}'::jsonb ->> 'b';
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb ->> 1;
-ERROR:  cannot call jsonb_array_element_text on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb ->> 'z';
-ERROR:  cannot call jsonb_object_field_text (jsonb ->> text) on a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 -- equality and inequality
 SELECT '{"x":"y"}'::jsonb = '{"x":"y"}'::jsonb;
  ?column? 
@@ -1269,9 +1345,33 @@ SELECT '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::jsonb#>>array['f2','1'];
 
 -- corner cases for same
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> '{}';
+          ?column?          
+----------------------------
+ {"a": {"b": {"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::jsonb #> '{}';
+ ?column?  
+-----------
+ [1, 2, 3]
+(1 row)
+
+select '"foo"'::jsonb #> '{}';
  ?column? 
 ----------
- 
+ "foo"
+(1 row)
+
+select '42'::jsonb #> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::jsonb #> '{}';
+ ?column? 
+----------
+ null
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a'];
@@ -1281,7 +1381,11 @@ select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a', null];
-ERROR:  cannot call jsonb_extract_path with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a', ''];
  ?column? 
 ----------
@@ -1336,13 +1440,55 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb #> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::jsonb #> array['1','b'];
+ ?column? 
+----------
+ null
+(1 row)
+
 select '"foo"'::jsonb #> array['z'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #> array['f2'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #> array['0'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> '{}';
+          ?column?          
+----------------------------
+ {"a": {"b": {"c": "foo"}}}
+(1 row)
+
+select '[1,2,3]'::jsonb #>> '{}';
+ ?column?  
+-----------
+ [1, 2, 3]
+(1 row)
+
+select '"foo"'::jsonb #>> '{}';
+ ?column? 
+----------
+ foo
+(1 row)
+
+select '42'::jsonb #>> '{}';
+ ?column? 
+----------
+ 42
+(1 row)
+
+select 'null'::jsonb #>> '{}';
  ?column? 
 ----------
  
@@ -1355,7 +1501,11 @@ select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a'];
 (1 row)
 
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a', null];
-ERROR:  cannot call jsonb_extract_path_text with null path elements
+ ?column? 
+----------
+ 
+(1 row)
+
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a', ''];
  ?column? 
 ----------
@@ -1410,12 +1560,30 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb #>> array['z','b'];
  
 (1 row)
 
+select '[{"b": "c"}, {"b": null}]'::jsonb #>> array['1','b'];
+ ?column? 
+----------
+ 
+(1 row)
+
 select '"foo"'::jsonb #>> array['z'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #>> array['f2'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 select '42'::jsonb #>> array['0'];
-ERROR:  cannot extract path from a scalar
+ ?column? 
+----------
+ 
+(1 row)
+
 -- array_elements
 SELECT jsonb_array_elements('[1,true,[1,[2,3]],null,{"f1":1,"f2":[7,8,9]},false]');
     jsonb_array_elements    
@@ -2105,7 +2273,11 @@ SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb -> 'e';
 (1 row)
 
 SELECT '{"n":null,"a":1,"b":[1,2],"c":{"1":2},"d":{"1":[2,3]}}'::jsonb -> 0; --expecting error
-ERROR:  cannot call jsonb_array_element (jsonb -> int) on an object
+ ?column? 
+----------
+ 
+(1 row)
+
 SELECT '["a","b","c",[1,2],null]'::jsonb -> 0;
  ?column? 
 ----------

src/test/regress/sql/json.sql

@@ -248,6 +248,7 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> '';
 select '[{"b": "c"}, {"b": "cc"}]'::json -> 1;
 select '[{"b": "c"}, {"b": "cc"}]'::json -> 3;
 select '[{"b": "c"}, {"b": "cc"}]'::json -> 'z';
+select '{"a": "c", "b": null}'::json -> 'b';
 select '"foo"'::json -> 1;
 select '"foo"'::json -> 'z';
 
@@ -259,6 +260,7 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json ->> '';
 select '[{"b": "c"}, {"b": "cc"}]'::json ->> 1;
 select '[{"b": "c"}, {"b": "cc"}]'::json ->> 3;
 select '[{"b": "c"}, {"b": "cc"}]'::json ->> 'z';
+select '{"a": "c", "b": null}'::json ->> 'b';
 select '"foo"'::json ->> 1;
 select '"foo"'::json ->> 'z';
 
@@ -312,6 +314,10 @@ select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>array['f2','1'];
 
 -- corner cases for same
 select '{"a": {"b":{"c": "foo"}}}'::json #> '{}';
+select '[1,2,3]'::json #> '{}';
+select '"foo"'::json #> '{}';
+select '42'::json #> '{}';
+select 'null'::json #> '{}';
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a'];
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a', null];
 select '{"a": {"b":{"c": "foo"}}}'::json #> array['a', ''];
@@ -323,11 +329,16 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json #> array['a','1','b'];
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json #> array['a','z','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::json #> array['1','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::json #> array['z','b'];
+select '[{"b": "c"}, {"b": null}]'::json #> array['1','b'];
 select '"foo"'::json #> array['z'];
 select '42'::json #> array['f2'];
 select '42'::json #> array['0'];
 
 select '{"a": {"b":{"c": "foo"}}}'::json #>> '{}';
+select '[1,2,3]'::json #>> '{}';
+select '"foo"'::json #>> '{}';
+select '42'::json #>> '{}';
+select 'null'::json #>> '{}';
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a'];
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a', null];
 select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a', ''];
@@ -339,6 +350,7 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json #>> array['a','1','b'];
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json #>> array['a','z','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::json #>> array['1','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::json #>> array['z','b'];
+select '[{"b": "c"}, {"b": null}]'::json #>> array['1','b'];
 select '"foo"'::json #>> array['z'];
 select '42'::json #>> array['f2'];
 select '42'::json #>> array['0'];

src/test/regress/sql/jsonb.sql

@@ -117,6 +117,7 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb -> '';
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 1;
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 3;
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 'z';
+select '{"a": "c", "b": null}'::jsonb -> 'b';
 select '"foo"'::jsonb -> 1;
 select '"foo"'::jsonb -> 'z';
 
@@ -128,6 +129,7 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> '';
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb ->> 1;
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb ->> 3;
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb ->> 'z';
+select '{"a": "c", "b": null}'::jsonb ->> 'b';
 select '"foo"'::jsonb ->> 1;
 select '"foo"'::jsonb ->> 'z';
 
@@ -283,6 +285,10 @@ SELECT '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::jsonb#>>array['f2','1'];
 
 -- corner cases for same
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> '{}';
+select '[1,2,3]'::jsonb #> '{}';
+select '"foo"'::jsonb #> '{}';
+select '42'::jsonb #> '{}';
+select 'null'::jsonb #> '{}';
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a'];
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a', null];
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #> array['a', ''];
@@ -294,11 +300,16 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb #> array['a','1','b'];
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb #> array['a','z','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb #> array['1','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb #> array['z','b'];
+select '[{"b": "c"}, {"b": null}]'::jsonb #> array['1','b'];
 select '"foo"'::jsonb #> array['z'];
 select '42'::jsonb #> array['f2'];
 select '42'::jsonb #> array['0'];
 
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> '{}';
+select '[1,2,3]'::jsonb #>> '{}';
+select '"foo"'::jsonb #>> '{}';
+select '42'::jsonb #>> '{}';
+select 'null'::jsonb #>> '{}';
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a'];
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a', null];
 select '{"a": {"b":{"c": "foo"}}}'::jsonb #>> array['a', ''];
@@ -310,6 +321,7 @@ select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb #>> array['a','1','b'];
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb #>> array['a','z','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb #>> array['1','b'];
 select '[{"b": "c"}, {"b": "cc"}]'::jsonb #>> array['z','b'];
+select '[{"b": "c"}, {"b": null}]'::jsonb #>> array['1','b'];
 select '"foo"'::jsonb #>> array['z'];
 select '42'::jsonb #>> array['f2'];
 select '42'::jsonb #>> array['0'];