Re: Extract numeric filed in JSONB more effectively

On Wed, Aug 16, 2023 at 2:28 PM Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com> wrote:
>
> update with the correct patch..

regression=# select proname, pg_catalog.pg_get_function_arguments(oid)
from pg_proc
where proname = 'jsonb_extract_path_type';
proname | pg_get_function_arguments
-------------------------+--------------------------------------------------------------------
jsonb_extract_path_type | from_json jsonb, VARIADIC path_elems
text[], target_oid anyelement
(1 row)

VARIADIC should be the last argument?

select jsonb_array_element_type(jsonb'[1231]',0, null::int);
now return null.
Should it return 1231?

regression=# select jsonb_array_element_type(jsonb'1231',0, 1::int);
jsonb_array_element_type
--------------------------
1231
(1 row)

not sure if it's ok. if you think it's not ok then:
+ if (!JB_ROOT_IS_ARRAY(jb))
+PG_RETURN_NULL();
change to
+if (JB_ROOT_IS_SCALAR(jb) || !JB_ROOT_IS_ARRAY(jb))
+PG_RETURN_NULL();

select jsonb_array_element_type(jsonb'[1231]',0, '1'::jsonb);
will crash, because jsonb_array_element_type call
cast_jsonbvalue_to_type then in switch case, it will go to
default part. in default part you have Assert(false);
also in cast_jsonbvalue_to_type, PG_RETURN_POINTER(NULL) code won't be reached.

in jsonb_cast_support function. you already have
!jsonb_cast_is_optimized(fexpr->funcresulttype)). then in the default
branch of cast_jsonbvalue_to_type, you can just elog(error, "can only
cast to xxx type"). jsonb_array_element_type, jsonb_object_field_type,
third argument is anyelement. so targetOid can be any datatype's oid.