Re: sql/json remaining issue

On Wed, Apr 10, 2024 at 4:39 PM Amit Langote <amitlangote09@gmail.com> wrote:
>
>
> Attached is a bit more polished version of that, which also addresses
> the error messages in JsonPathQuery() and JsonPathValue().  I noticed
> that there was comment I had written at one point during JSON_TABLE()
> hacking that said that we should be doing this.
>
> I've also added an open item for this.
>

`
 | NESTED [ PATH ] json_path_specification [ AS json_path_name ]
COLUMNS ( json_table_column [, ...] )
NESTED [ PATH ] json_path_specification [ AS json_path_name ] COLUMNS
( json_table_column [, ...] )
`
 "json_path_specification" should be "path_expression"?

your explanation about memory usage is clear to me!


The following are minor cosmetic issues while applying v2.
+errmsg("JSON path expression in JSON_VALUE should return singleton
scalar item")));
"singleton" is not intuitive to me.
Then I looked around.
https://www.postgresql.org/search/?u=%2Fdocs%2F16%2F&q=singleton
There is only one appearance of "singleton" in the manual.
then I wonder what's the difference between
22038 ERRCODE_SINGLETON_SQL_JSON_ITEM_REQUIRED
2203F ERRCODE_SQL_JSON_SCALAR_REQUIRED

i assume '{"hello":"world"}'  is a singleton, but not a scalar item?
if so, then I think the error message within the "if (count > 1)"
branch in JsonPathValue
should use ERRCODE_SINGLETON_SQL_JSON_ITEM_REQUIRED
within the "if (!IsAJsonbScalar(res))" branch should use
ERRCODE_SQL_JSON_SCALAR_REQUIRED
?


errhint("Use WITH WRAPPER clause to wrap SQL/JSON item sequence into array.")));
maybe
errhint("Use WITH WRAPPER clause to wrap SQL/JSON items into array.")));
or
errhint("Use WITH WRAPPER clause to wrap SQL/JSON item sequences into
array.")));


+ if (column_name)
+ ereport(ERROR,
+ (errcode(ERRCODE_MORE_THAN_ONE_SQL_JSON_ITEM),
+ errmsg("JSON path expression for column \"%s\" should return
singleton scalar item",
+ column_name)));
+ else
+ ereport(ERROR,
+ (errcode(ERRCODE_SQL_JSON_SCALAR_REQUIRED),
+ errmsg("JSON path expression in JSON_VALUE should return singleton
scalar item")));
the error message seems similar, but the error code is different?
both within "if (count > 1)" and "if (!IsAJsonbScalar(res))" branch.


in src/include/utils/jsonpath.h, comments
/* SQL/JSON item */
should be
/* SQL/JSON query functions */


elog(ERROR, "unrecognized json wrapper %d", wrapper);
should be
elog(ERROR, "unrecognized json wrapper %d", (int) wrapper);