-- Content for Post A (is searched)
-- Meta data for post A (is searched)
----- Post object field points to POST B
------- Content for Post B (cannot be searched)
------- Meta data for Post B (cannot be searched)
In order to do what you want you need to not only have a pointer to post B but you need to import all of the content from Post B into Post A, basically duplicating all of Posts B’s data.
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