Support of sql realtions in plugin execution

[Yaroher2442]

What do you want to change?

I try to write plugin wich generate some ORM-like helpers.
My code need to know about table primary keys (normal and composite) and tables relations.
In my case, knowledge of the relations and PKs is needed when calling the plugin.

I can offer 2 strategies:

1. Add values ​​from sql constraint to the information for (proto) plugin.
   For example "NOT NULL REFERENCES (id)".
   then the plugin itself is responsible for parsing the relations.

2. Get relations from your lexer and pass them separately to proto

What database engines need to be changed?

PostgreSQL

What programming language backends need to be changed?

Go