Re: Better error reporting from extension scripts (Was: Extend ALTER OPERATOR)

On Mon, Oct 14, 2024 at 1:13 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> > so 12. 10. 2024 v 9:33 odesílatel jian he <jian(dot)universality(at)gmail(dot)com>
> > napsal:
> >> + /*
> >> + * If we have a location (which, as said above, we really always should)
> >> + * then report a line number to aid in localizing problems in big scripts.
> >> + */
> >> + if (location >= 0)
> >> so this part will always be true?
>
> > yes, after CleanQuerytext the location should not be -1 ever
>
> Right, but we might not have entered either of those previous
> if-blocks.

in src/backend/parser/gram.y
your makeRawStmt changes (v4) seem to guarantee that
RawStmt->stmt_location >= 0.
other places {DefineView,DoCopy,PrepareQuery} use makeNode(RawStmt),
In these cases, I am not so sure RawStmt->stmt_location >=0 is always true.

in execute_sql_string

raw_parsetree_list = pg_parse_query(sql);
dest = CreateDestReceiver(DestNone);
foreach(lc1, raw_parsetree_list)
{
RawStmt *parsetree = lfirst_node(RawStmt, lc1);
MemoryContext per_parsetree_context,
oldcontext;
List *stmt_list;
ListCell *lc2;
callback_arg.stmt_location = parsetree->stmt_location;
callback_arg.stmt_len = parsetree->stmt_len;
per_parsetree_context =
AllocSetContextCreate(CurrentMemoryContext,
"execute_sql_string per-statement context",
ALLOCSET_DEFAULT_SIZES);
oldcontext = MemoryContextSwitchTo(per_parsetree_context);
CommandCounterIncrement();
stmt_list = pg_analyze_and_rewrite_fixedparams(parsetree,
sql,
NULL,
0,
NULL);

Based on the above code, we do
`callback_arg.stmt_location = parsetree->stmt_location;`
pg_parse_query(sql) doesn't use script_error_callback.

So if we are in script_error_callback
`int location = callback_arg->stmt_location;`
location >= 0 will be always true?

> The question here is whether the raw parser (gram.y)
> ever throws an error that doesn't include a cursor position. IMO it
> shouldn't, but a quick look through gram.y finds a few ereports that
> lack parser_errposition. We could go fix those, and probably should,
> but imagining that none will ever be introduced again seems like
> folly.
>

I don't know how to add the error position inside the function
insertSelectOptions.
maybe we can add
`parser_errposition(exprLocation(limitClause->limitCount))));`
but limitCount position is a nearby position.
I am also not sure about func mergeTableFuncParameters.

for other places in gram.y, I've added error positions for ereport
that lack it , please check the attached.