Yes Nick, this option is checked in our application. Our application is hosted for two different countries. As a regulatory compliance I want to keep notes for each country tobe stored in country specific table, not in pc_Workattach table. Also in the same way I am trying to keep a specific class inherited from Link-Attachment class to this country specific table. 

In response to "I observed if we use OOTB Link-Attachment class then only the indexing is triggered" : I can see the entries for FTSIndexer only when I use default Link-Attachment class while storing the attachment. My doubt is how we can trigger Indexing (For Elastic Search) for the classes which inherits the Link-Attachment class.