Re: printing JsonbPair values of input JSONB on server side?

Thanks a lot. Fixing `CREATE FUNCTION` statement fixed the crash issue.

On Tue, Mar 19, 2019 at 3:18 PM Michel Pelletier <pelletier(dot)michel(at)gmail(dot)com>
wrote:

> For server crashes you can't beat gdb in my opinion. It's a challenge but
> worth it in the long run to have gdb skills if you're coding in C (or
> Python, since pdb shares many of gdb's keybindings).
>
> But just looking at the function I don't see what's immediately wrong,
> what's your CREATE FUNCTION statement look like?
>
> On Tue, Mar 19, 2019 at 1:08 PM T L <tinlyx(at)gmail(dot)com> wrote:
>
>> Thanks a lot for the hint. I've used the iteration style and cleaned up
>> the code as far as I can.
>> It now correctly prints the keys and values, but the server crashes near
>> function return.
>>
>> Any suggestions?
>>
>> -- function code --
>>
>> PG_FUNCTION_INFO_V1(print_kv_pair);
>> Datum
>> print_kv_pair(PG_FUNCTION_ARGS)
>> {
>> //1. extracting JsonbValue
>> Jsonb *jb = PG_GETARG_JSONB_P(0);
>> JsonbIterator *it;
>> JsonbValue v;
>> JsonbIteratorToken r;
>> JsonbParseState *state = NULL;
>>
>> if (jb == NULL)
>> PG_RETURN_BOOL(false);
>>
>> if (!JB_ROOT_IS_OBJECT(jb))
>> ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
>> errmsg("Can only take objects")));
>>
>> it = JsonbIteratorInit(&jb->root);
>> r = JsonbIteratorNext(&it, &v, false);
>> if (r != WJB_BEGIN_OBJECT)
>> ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
>> errmsg("Iterator was not an object")));
>>
>> //2. iterating through key-value pairs
>> char *buf;
>> while ((r = JsonbIteratorNext(&it, &v, true)) != WJB_DONE)
>> {
>> switch (r) {
>> case WJB_KEY:
>> buf = pnstrdup(v.val.string.val, v.val.string.len);
>> elog(NOTICE, "print_kv_pair(): k = %s", buf); //debug
>> break;
>> case WJB_VALUE:
>> if (v.type != jbvNumeric) {
>> ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
>> errmsg("value must be numeric")));
>> }
>> elog(NOTICE, "print_kv_pair(): v = %s",
>> DatumGetCString(DirectFunctionCall1(numeric_out,
>> NumericGetDatum(v.val.numeric))) ); //debug
>> break;
>> case WJB_END_OBJECT:
>> break;
>> default:
>> elog(ERROR, "invalid JsonbIteratorNext rc: %d", (int ) r);
>> }
>> }
>> elog(NOTICE, "print_kv_pair(): ok4");
>>
>> PG_RETURN_BOOL(true);
>> }
>>
>> -- output --
>>
>> => select print_kv_pair('{"a":1, "b": 2}');
>> NOTICE: print_kv_pair(): k = a
>> NOTICE: print_kv_pair(): v = 1
>> NOTICE: print_kv_pair(): k = b
>> NOTICE: print_kv_pair(): v = 2
>> NOTICE: print_kv_pair(): ok4
>> server closed the connection unexpectedly
>> This probably means the server terminated abnormally
>> before or while processing the request.
>> The connection to the server was lost. Attempting reset: Failed.
>> !>
>>
>>
>> On Tue, Mar 19, 2019 at 2:22 PM Michel Pelletier <
>> pelletier(dot)michel(at)gmail(dot)com> wrote:
>>
>>> jsonb_each is a wrapper around each_worker_jsonb. It produces a row for
>>> every key/value pair in an object.
>>>
>>>
>>> https://doxygen.postgresql.org/jsonfuncs_8c.html#a7511a3aa3918eb956f3f4211d07bdbb0
>>>
>>> the iteration is:
>>>
>>> while ((r = JsonbIteratorNext(&it, &v, skipNested)) != WJB_DONE)
>>>
>>>
>>>
>>> On Tue, Mar 19, 2019 at 11:20 AM T L <tinlyx(at)gmail(dot)com> wrote:
>>>
>>>> I need this in my C code on the server side. Any link to the
>>>> `jsonb_each` for this? Examples I found in a quick search are on the client
>>>> side in SQL.
>>>>
>>>> I am just confused about the various jsonb types and how to effectively
>>>> extract values and convert between them:
>>>>
>>>> There are Jsonb, JsonbValue (plus the associated JsonbPair ) to begin
>>>> with. The ` JsonbToCStringWorker ` example that Andrew pointed out uses
>>>> still another "JsonbContainer" type.
>>>> But the type I get from "PG_GETARG_JSONB_P" is Jsonb. And it doesn't
>>>> fit into " JsonbContainer" or the pointer math about "JsonPair" that I
>>>> found online.
>>>>
>>>> What I am struggling with adapting some of the iterator code I saw is
>>>> how to delete irrelevant code without breaking it. My use case is very
>>>> restricted and handles hstore-like jsonb's.
>>>> I don't need or want the code to have the ability to descend into
>>>> nested objects or handle arrays etc., as they are invalid input in my case.
>>>>
>>>> I thought the pointer math example I found is easier to adapt, but I
>>>> couldn't get a valid "JsonbPair" from the input parameter to feed into the
>>>> pointer math.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On Tue, Mar 19, 2019 at 9:50 AM Michel Pelletier <
>>>> pelletier(dot)michel(at)gmail(dot)com> wrote:
>>>>
>>>>> Yeah I'm not sure why you're looping using pointer math, the iterators
>>>>> are there to provide that service. Another function to check out
>>>>> 'jsonb_each', other than the set returning function parts, it does what it
>>>>> looks like your are trying to do.
>>>>>
>>>>> -Michel
>>>>>
>>>>> On Mon, Mar 18, 2019 at 4:12 PM Andrew Gierth <
>>>>> andrew(at)tao11(dot)riddles(dot)org(dot)uk> wrote:
>>>>>
>>>>>> >>>>> "T" == T L <tinlyx(at)gmail(dot)com> writes:
>>>>>>
>>>>>> T> Below is my test. It prints a strange character instead of "a";
>>>>>> and
>>>>>> T> says that the value isn't numeric.
>>>>>>
>>>>>> Yeah, there's plenty else wrong with your code.
>>>>>>
>>>>>> Did you look at how JsonbToCStringWorker does it? that looks like the
>>>>>> best example I can find on a quick scan.
>>>>>>
>>>>>> --
>>>>>> Andrew (irc:RhodiumToad)
>>>>>>
>>>>>>