Mastering PostgreSQL 10

Optimizations by example

To demonstrate how the optimizer works, I have compiled an example, one which I have used over the years in PostgreSQL training. Suppose there are three tables:

CREATE TABLE a (aid int, ...);         -- 100 million rows
CREATE TABLE b (bid int, ...);         -- 200 million rows 
CREATE TABLE c (cid int, ...);         -- 300 million rows 

Let us assume further that those tables contain millions, or maybe hundreds of millions, of rows. In addition to that, there are indexes:

CREATE INDEX idx_a ON a (aid); 
CREATE INDEX idx_b ON b (bid); 
CREATE INDEX idx_c ON c (cid);CREATE VIEW v AS SELECT * FROM a, bWHERE aid = bid; 

Finally, there is a view joining the first two tables together.

Let us suppose now the end user wants to run the following query. ...