Mastering PostgreSQL 10

Inlining the view

The first transformation done by the optimizer is to inline views. Here is what happens:

SELECT * FROM (   SELECT *    FROM a, b    WHERE aid = bid) AS v, c WHERE v.aid = c.cid       AND cid = 4;

The view is inlined and transformed to a subselect. What does this one buy us? Actually, nothing. All it does is to open the door for further optimization, which will really be a game changer for this query.