function to parse json format string prop

[wey-gu]

context: https://discuss.nebula-graph.com.cn/t/topic/6991

[jievince]

Return a map?

[akshatakulkarni25]

Hello. I am Akshata Kulkarni. I am interested in working on this issue. Is this issue still open to work on??It would be my first issue. Could you also please guide through this issue.Thanks

[wey-gu]

Dear @akshatakulkarni25 ,

Welcome to the community, this issue is still open!

I think a function similar to JSON_EXTRACT could be introduced here.

@jievince do you see it as reasonable/feasible?

why

The motivation of this issue was NebulaGraph doesn't support nested datatype, in some cases, user may like to serialize JSON data in a string as properties of Tag/edgeType, thus, this function would enable data extracting in return expression.
(We should consider stopping user from using it in filter expression, as this will lead to a data full scan. @jievince ? )

what

• It takes a string and returns a map:

YIELD JSON_EXTRACT('{"a": 1, "b": 2, "c": {"d": 4}}') AS map_foo
+-------------------------+
| map_foo                 |
+-------------------------+
| {a: 1, b: 2, c: {d: 4}} |
+-------------------------+

- It takes path as args, too (@jievince do you think this is needed?, this makes the function a lot more complex to be implemented)

YIELD JSON_EXTRACT('{"a": 1, "b": 2, "c": {"d": 4}}', '$.c') AS map_foo_dot_c
+-----------+
| map_foo   |
+-----------+
| {d: 4}    |
+-----------+

[jievince]

Dear @akshatakulkarni25 ,

Welcome to the community, this issue is still open!

I think a function similar to JSON_EXTRACT could be introduced here.

@jievince do you see it as reasonable/feasible?

why

The motivation of this issue was NebulaGraph doesn't support nested datatype, in some cases, user may like to serialize JSON data in a string as properties of Tag/edgeType, thus, this function would enable data extracting in return expression. (We should consider stopping user from using it in filter expression, as this will lead to a data full scan. @jievince ? )

what

• It takes a string and returns a map:

YIELD JSON_EXTRACT('{"a": 1, "b": 2, "c": {"d": 4}}') AS map_foo
+-------------------------+
| map_foo                 |
+-------------------------+
| {a: 1, b: 2, c: {d: 4}} |
+-------------------------+

• It takes path as args, too (@jievince do you think this is needed?, this makes the function a lot more complex to be implemented)

YIELD JSON_EXTRACT('{"a": 1, "b": 2, "c": {"d": 4}}', '$.c') AS map_foo_dot_c
+-----------+
| map_foo   |
+-----------+
| {d: 4}    |
+-----------+

That's a good point. But it may be a bit troublesome to implement all the json functions in mysql. I suggest you could first implement a simple function, such as convertToMap, which takes a json string, and returns a map value it represents.

[jievince]

The implementation of the builtin functions is here: https://github.com/vesoft-inc/nebula/blob/master/src/common/function/FunctionManager.cpp

Looking forward to your contribution.

[wey-gu]

also, one PR on introducing functions here

Let us know your questions any time :) @akshatakulkarni25

[akshatakulkarni25]

Respected Sir, Thank you for your reply. I look forward to learning from and contributing to the repository. Could I also reach out to you in case I have any doubts or queries throughout the process through emails Thank you. Regards, Akshata Kulkarni

…

On Mon, 5 Sep 2022 at 1:43 PM, Wey Gu ***@***.***> wrote: also, one PR on introducing functions here <#4526> — Reply to this email directly, view it on GitHub <#3513 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AYHIZFKB7YX3VH3B56ULTC3V4WTSHANCNFSM5KPCCL2A> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[wey-gu]

Dear @akshatakulkarni25 ,
Sure, you could mail/slack me when needed :)

• email could be found: https://siwei.io/en/about/#contact
• slack

[wey-gu]

Hi @akshatakulkarni25

May I know your status on this issue? It's ok if you could not make it, I am trying to prepare a PR on it, and in case yours is ready, we could co-work on yours instead.

Thanks!

[jinyingsunny]

checked on 3.3-rc
checked on 3.3-ent-rc