Multicolumn Persistent List/Array Property

Question

Question

Paul Riker · Oct 17, 2016

#Object Data Model #Relational Tables #Caché

I have a persistent class where I am logging each CCDA I receive. I want to store all of the providers associated to that CCDA (many to one). In a relational database, I would have a child table with a foreign key to the primary table. I'm guessing the equivalent to Cache would be

1. Create a custom class (ProviderList) with the properties I want to store.

2. Add the class as a property of my CCDA persistent class.

Property Providers as Array of ProviderList (SQLProjection = "table/column";

Am I on the right track?

Discussion (4)0

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Warlin Garcia · Oct 17, 2016

Relationships load a "collection" of pointers to the members of the relationship. Objects are loaded to memory only when accessed. Pretty much how Arrays work as well. In essence Arrays and Relationships work the same. Relationships provide the extra referential integrity.

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score 0 · Answer 1 · 2016-10-17T11:30:26-04:00

Generally yes, but here's some thoughts:

Use List, instead of Array whenever possible
Specify STORAGEDEFAULT as "array" to project list collection properties as child tables

Property Providers as List of ProviderList(SQLProjection = "table/column", STORAGEDEFAULT = "array");

score 0 · Answer 2 · 2016-10-17T11:44:36-04:00

You're on the right track, however, depending on your needs, always prefer a relationship over a "plain" array/list. One of the biggest benefits is the referential integrity you get "out of the box".

score 0 · Answer 3 · 2016-10-17T11:55:00-04:00

The caveat with relationships is that all of the many objects are loaded or none are. That may present a performance problem if you have a one-many relationship with thousands of rows on the many side.