Re: Extract numeric filed in JSONB more effectively

On Tue, Aug 15, 2023 at 1:24 PM Pavel Stehule <pavel.stehule@gmail.com>
wrote:

> Hi
>
> út 15. 8. 2023 v 5:24 odesílatel Andy Fan <zhihui.fan1213@gmail.com>
> napsal:
>
>>
>>>  jsonb_extract_xx_type just cares about the argtype, but
>>> 'explain select xx'  will still access the const->constvalue.
>>> const->constvalue is 0 which is set by makeNullConst currently,
>>> and it is ok for the current supported type.
>>>
>>
>> The exception is numeric data type, the constvalue can't be 0.
>> so hack it with the below line.  maybe not good enough,  but I
>> have no better solution now.
>>
>> +                       Const   *target =
>>  makeNullConst(fexpr->funcresulttype,
>> +
>>                -1,
>> +
>>                InvalidOid);
>> +                       /*
>> +                        * Since all the above functions are strict, we
>> can't input
>> +                        * a NULL value.
>> +                        */
>> +                       target->constisnull = false;
>> +
>> +                       Assert(target->constbyval || target->consttype ==
>> NUMERICOID);
>> +
>> +                       /* Mock a valid datum for !constbyval type. */
>> +                       if (fexpr->funcresulttype == NUMERICOID)
>> +                               target->constvalue =
>> DirectFunctionCall1(numeric_in, CStringGetDatum("0"));
>>
>>
> Personally I think this workaround is too dirty, and better to use a
> strict function (I believe so the overhead for NULL values is acceptable).
>

In the patch v8,  I created a new routine named makeDummyConst,
which just sits by makeNullConst. It may be helpful to some extent.
a).  The code is self-document for the user/reader.  b).  We have a
central place to maintain this routine.

Besides the framework,  the troubles for the reviewer may be if the
code has some corner case issue or behavior changes. Especially
I have some code refactor when working on jsonb_extract_path.
so the attached test.sql is designed for this.  I have compared the
result between master and patched version and I think reviewer
can do some extra testing with it.

v8 is the finished version in my mind, so I think it is ready for review
now.

-- 
Best Regards
Andy Fan