Nested CDTs

RE: Nested CDTs

rajeshs — Mon, 13 Aug 2018 05:56:01 GMT

1 level of nested CDT is always recommended, but please make sure that child CDT is not unbounded. If many-to-many relationship is required then create separate CDT for parent and child node and identify a field which is common in both (act as a foreign key).

RE: Nested CDTs

sahithip120 — Tue, 07 Aug 2018 01:19:40 GMT

use a!flatten()

RE: Nested CDTs

chandu — Thu, 14 Jun 2018 11:15:48 GMT

If you are on 17.3+ and above you can use a!flatten, else you can write your own expression rule.

RE: Nested CDTs

soujanyac0001 — Thu, 14 Jun 2018 10:07:01 GMT

Can anyone tell me how to flatten a nested cdt. I have tried using expandcdt(), but it didnt work for me.

RE: Nested CDTs

TJ — Tue, 06 Feb 2018 08:23:48 GMT

I agree to what Alok Kumar mentioned. You should try not to go for Nested CDTs as it may cause several issues.

RE: Nested CDTs

smriti p0001 — Tue, 06 Feb 2018 08:06:02 GMT

Appian generally recommends one level only, but in real time scenario specially when you are using services then lot of nesting is required, however it may lead to performance issues later.

RE: Nested CDTs

vineeta6579 — Mon, 23 Oct 2017 02:11:46 GMT

One of the disadvantages of nested CDT design is N+1 Problem, Ref below doc link for details.

community.appian.com/.../database-performance-best-practices

RE: Nested CDTs

Jamal Case — Sat, 21 Oct 2017 22:02:58 GMT

Thank you all for the feedback.

RE: Nested CDTs

aloks0189 — Fri, 20 Oct 2017 12:50:29 GMT

Adding to above points, also when you are working with Nested CDT, you might face difficulties in many aspect such as,

While converting this data, to JSON and getting the dictionary back from JSON, will be pretty difficult.

Also when you want to debug these data in UI or process model, it will be difficult while compared to normal CDT.

And I believe, we should not go for nested CDT even for single level, if we have any other choice remain,

yes I agree, as per Appian statement, upto 1 level of nested is ok or good, but I believe Appian suggests, if at all you want to go for nested CDT then go for 1 level but I believe if you can achieve the same using plain CDT, then you should always go for plain CDT

RE: Nested CDTs

vijayd — Fri, 20 Oct 2017 10:37:08 GMT

Some more issues could lead into complex looping when you are working in Nested CDTs which would potentially lead to High health checks. However it varies from case to case.

RE: Nested CDTs

ankita0004 — Fri, 20 Oct 2017 05:11:27 GMT

Nested CDT has some advantages as well as some limitations also.

Advantages:

1. There is no need for creation of view if we use nested cdt.
2. We can fetch data of child cdt from parent cdt

Limitations:

It has much more limitations than advantages:

1. Debugging of process instance is much difficult.
2. We can't give a name of column in master table.
3. Unnecessarily we need to fetch child table data

and many more disadvantage So View is much better approach than nested cdts.

RE: Nested CDTs

chandu — Thu, 19 Oct 2017 17:44:14 GMT

Hi Jamal,
As u aware that Appian recommends one level of nested CDT. As far as i know these are the following are the limitations .
if you want to get only parent cdt data, you will get child cdt data as well.In one to many relation ship this results in pulling unnecessarily child data as well.
Additional coding needs to be done to show the data in grids/reports that is coming from nested CDTs[typically when not in one one relationship]
[Need to confirm the below Usecase showing the nested CDT in script task output tab]
Suppose you a have a nested CDT structure as below.
CDT1
field1InCDT1
CDT2
field2InCDT2ofCDT1
CDT3
field3InCDT3ofCDT2ofCDT1

In script task outputs tab, I think you cannot store a value into the field CDT1.CDT2.CDT3.field3InCDT3ofCDT2ofCDT1 as Outupt tab will show two levels deep only.

I'm really interested in digging more on nested CDT's. Lets see what other practitioners suggests.

RE: Nested CDTs

John M — Thu, 19 Oct 2017 16:41:19 GMT

Jamal,

According to the playbook they should not be more than 1 level deep (community.appian.com/.../project-implementation-best-practices-checklist). You can also find a list of db best practices here (community.appian.com/.../database-performance-best-practices) which discusses some drawbacks of using nested cdts