"id_str" like primary_key in Postgree DB


Hello, guys.

I’m concerned with one thing. I have three sqlite3 databases full of tweets and I want to put them together in a single Postgres DB. In this process, I thought it could be a efficient way to put “id_str” like primary_key. But after inserting 2 of these 3 databases into the single new database. It got much less tweets than those 2 databases that I tried to insert. I’m wondering why it’s happening. I’m not sure if it’s causing that, but alongside the original tweets there are lots of them who are retweets.