Re: Extended Statistics set/restore/clear functions.

On Wed, Jan 29, 2025 at 2:50 AM jian he <jian(dot)universality(at)gmail(dot)com> wrote:

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

I think my initial reaction is to just refuse those special values, but
I'll look into the parsing code to see what can be done.

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)
>

I don't have a good answer as to what should happen here. Special cases
like this make Tomas' suggestion to change the in/out format more
attractive.

>
>
> 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;
> ?
>

The compiler isn't complaining so far, but I see no harm in it.