Re: SQL/JSON path issues/questions

On 6/17/19 11:36 AM, Alexander Korotkov wrote:
> I'm going to push attached 3 patches if no objections.
>
> Regarding 0003-Separate-two-distinctive-json-errors.patch, I think it
> requires more thoughts.
>
>          RETURN_ERROR(ereport(ERROR,
>                               (errcode(ERRCODE_SINGLETON_JSON_ITEM_REQUIRED),
>                                errmsg("left operand of jsonpath
> operator %s is not a single numeric value",
> -                                    jspOperationName(jsp->type)))));
> +                                    jspOperationName(jsp->type)),
> +                             (llen != 1 ?
> +                              errdetail("It was an array with %d
> elements.", llen):
> +                              errdetail("The only element was not a
> numeric.")))));
>
> When we have more than 1 value, it's no exactly array.  Jsonpath can
> extract values from various parts of json document, which never
> constitute and array.  Should we say something like "There are %d
> values"?  Also, probably we should display the type of single element
> if it's not numeric.  jsonb_path_match() also throws
> ERRCODE_SINGLETON_JSON_ITEM_REQUIRED, should we add similar
> errdetail() there?
>
> ------
> Alexander Korotkov
> Postgres Professional: http://www.postgrespro.com
> The Russian Postgres Company

Hi Alexander,

While I have no objections to the proposed fixes, I think we can further 
improve patch 0003 and the text it refers to.
In attempt to clarify jsonpath docs and address the concern that ? is 
hard to trace in the current text, I'd also like to propose patch 0004.
Please see both of them attached.

-- 
Liudmila Mantrova
Technical writer at Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company