Mastering PostgreSQL 10

Trying it all out

Now that all those optimizations have been discussed, it is time to see which plan PostgreSQL might create for us:

test=# explain SELECT * FROM v, c WHERE v.aid = c.cid AND cid = 4; 
                          QUERY PLAN ----------------------------------------------------------------  Nested Loop (cost=1.71..17.78 rows=1 width=12)    -> Nested Loop (cost=1.14..9.18 rows=1 width=8)          -> Index Only Scan using idx_a on a                (cost=0.57..4.58 rows=1 width=4)                Index Cond: (aid = 4)          -> Index Only Scan using idx_b on b                (cost=0.57..4.59 rows=1 width=4)                Index Cond: (bid = 4)    -> Index Only Scan using idx_c on c                (cost=0.57..8.59 rows=1 width=4)          Index Cond: (cid = 4) (8 rows) 

As you can see, PostgreSQL will use three indexes. It is also interesting to see that ...