CDT's

RE: CDT's

pankajm949 — Mon, 06 Aug 2018 13:52:17 GMT

Hi Divya,

First of all, Appian recommends to use one level of nesting for CDTs. Nesting of CDTs can also impact the performance.

Apart from these, what I have observed is If we are nesting multiple type CDT inside another multiple type nested CDT, then we cannot map the fields of last level CDT inside Process Model. Also, we cannot access properly the fields of last level CDT inside our rules and other objects.

RE: CDT's

josep — Mon, 06 Aug 2018 11:51:40 GMT

Hello Divya,

I really liked all the posts above.

I just wanted to add As a little background a reason for that best practice. Appian CDTs/datastore uses the “improved/simplified version” of the JPA. So one of the inheritated problems is that “nested eager relationships” (which for us in Appian is the nested CDT) because part of the simplification is that all CDTs use eager loading, which means when nested and you query the main table it will try to join all the nested CDTs/tables to get your information. So if you have 1 level nested for n amount of fields the query will join the main table + n number of nested Tables(CDTs).

Imagine if you had multiple nested levels, that can be a huge join and problem, it means time and load to the server. Even that the JPA has certain limit on the joins let’s say 30 joins per query.

Most of the times when you query a CDT you don’t really need all those joins and all the fields from all the tables, that’s where the views comes to play, on the views you can select each required field and you decide which joins are really required at that particular query
.
One common way to see it is you have datastore for tables and one datastore for views. The tables will be to insert/update , and the views to query and display data to the user.

Hope this helps.

Jose

RE: CDT's

Preji P — Mon, 06 Aug 2018 07:21:18 GMT

hi Divya,
I very much agree with what Abhay has stated that we should avoid making use of Nested CDTs, as they highly impact our performance; but if your logic needs a nested CDT solution then Appian recommends you to have 1 level of nesting.
Hope this has answer you query.

Thanks
Preji

RE: CDT's

Abhay Giri — Mon, 14 May 2018 00:17:47 GMT

Hi Divya,

you can refer this link https://community.appian.com/discussions/f/best-practices/11277/nested-cdts for more about nesting level, advantage & disadvantage.

Regards

Abhay

RE: CDT's

aloks0189 — Sun, 13 May 2018 22:37:47 GMT

Hi divya chakka as per the best practices guidelines, you can go for 1 level of nested CDT but as per my understanding, you should avoid using nested CDT approach as much as you can. Fir further details, I recommend you to visit the above link mentioned by @Dmitry

RE: CDT's

Dmitry S — Sun, 13 May 2018 12:52:19 GMT

There was a good discussion with a lot of answers already on this topic. Summary: Appian generally recommends one level of nested CDTs only. More details here: community.appian.com/.../nested-cdts