Re: Extended Statistics set/restore/clear functions.

hi.

select '{"1, 0B100101":"NaN"}'::pg_ndistinct;
      pg_ndistinct
------------------------
 {"1, 37": -2147483648}
(1 row)

this is not what we expected?
For the VALUE part of pg_ndistinct, float8 has 3 special values: inf, -inf, NaN.

For the key part of pg_ndistinct, see example.
select '{"1, 16\t":"1"}'::pg_ndistinct;
here \t is not tab character, ascii 9. it's two characters: backslash
and character "t".
so here it should error out?
(apply this to \n, \r, \b)

pg_ndistinct_in(PG_FUNCTION_ARGS)
ending part should be:

    freeJsonLexContext(lex);
    if (result == JSON_SUCCESS)
    {
        ......
    }
    else
    {
       ereturn(parse_state.escontext, (Datum) 0,
                    errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                    errmsg("malformed pg_ndistinct: \"%s\"", str),
                    errdetail("Must be valid JSON."));
       PG_RETURN_NULL();
    }
result should be either JSON_SUCCESS or anything else.



all these functions:
ndistinct_object_start, ndistinct_array_start,
ndistinct_object_field_start, ndistinct_array_element_start
have
ndistinctParseState *parse = state;

do we need to change it to
ndistinctParseState *parse = (ndistinctParseState *)state;
?