Fix core dump in jsonb #> operator, and add regression test cases.

jsonb's #> operator segfaulted (dereferencing a null pointer) if the RHS
was a zero-length array, as reported in bug #11207 from Justin Van Winkle.
json's #> operator returns NULL in such cases, so for the moment let's
make jsonb act likewise.

Also add a bunch of regression test queries memorializing the -> and #>
operators' behavior for this and other corner cases.

There is a good argument for changing some of these behaviors, as they
are not very consistent with each other, and throwing an error isn't
necessarily a desirable behavior for operators that are likely to be
used in indexes.  However, everybody can agree that a core dump is the
Wrong Thing, and we need test cases even if we decide to change their
expected output later.

1 files changed, 40 insertions, 9 deletions

diff --git a/src/test/regress/sql/json.sql b/src/test/regress/sql/json.sql
index ae65ef6921e..964d5baa2a4 100644
--- a/src/test/regress/sql/json.sql
+++ b/src/test/regress/sql/json.sql
@@ -238,6 +238,17 @@ select (test_json->>3) is null as expect_true
 from test_json
 where json_type = 'array';
 
+-- corner cases
+
+select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> null::text;
+select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> null::int;
+select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> 1;
+select '{"a": [{"b": "c"}, {"b": "cc"}]}'::json -> 'z';
+select '[{"b": "c"}, {"b": "cc"}]'::json -> 1;
+select '[{"b": "c"}, {"b": "cc"}]'::json -> 3;
+select '[{"b": "c"}, {"b": "cc"}]'::json -> 'z';
+select '"foo"'::json -> 1;
+select '"foo"'::json -> 'z';
 
 -- array length
 
@@ -281,20 +292,40 @@ select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>array['f4','f6'];
 select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>array['f2'];
 select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>array['f2','0'];
 select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>array['f2','1'];
+
 select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>>array['f4','f6'];
 select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>>array['f2'];
 select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>array['f2','0'];
 select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>array['f2','1'];
 
--- same using array literals
-select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>'{f4,f6}';
-select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>'{f2}';
-select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>'{f2,0}';
-select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>'{f2,1}';
-select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>>'{f4,f6}';
-select '{"f2":{"f3":1},"f4":{"f5":99,"f6":"stringy"}}'::json#>>'{f2}';
-select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>'{f2,0}';
-select '{"f2":["f3",1],"f4":{"f5":99,"f6":"stringy"}}'::json#>>'{f2,1}';
+-- corner cases for same
+select '{"a": {"b":{"c": "foo"}}}'::json #> array[]::text[];
+select '{"a": {"b":{"c": "foo"}}}'::json #> array['a'];
+select '{"a": {"b":{"c": "foo"}}}'::json #> array['a','b'];
+select '{"a": {"b":{"c": "foo"}}}'::json #> array['a','b','c'];
+select '{"a": {"b":{"c": "foo"}}}'::json #> array['a','b','c','d'];
+select '{"a": {"b":{"c": "foo"}}}'::json #> array['a','z','c'];
+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 '"foo"'::json #> array['z'];
+select '42'::json #> array['f2'];
+select '42'::json #> array['0'];
+
+select '{"a": {"b":{"c": "foo"}}}'::json #>> array[]::text[];
+select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a'];
+select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a','b'];
+select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a','b','c'];
+select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a','b','c','d'];
+select '{"a": {"b":{"c": "foo"}}}'::json #>> array['a','z','c'];
+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 '"foo"'::json #>> array['z'];
+select '42'::json #>> array['f2'];
+select '42'::json #>> array['0'];
 
 -- array_elements