Result

Sometimes a node just needs to return a result computed by a statement:

EXPLAIN ANALYZE SELECT 1;
QUERY PLAN 
----------
Result  (cost=0.00..0.01 rows=1 width=0) (actual time=0.003..0.005 rows=1 loops=1)
 Total runtime: 0.038 ms

Result nodes are basically quick pass-through nodes when individual values are being operated on, instead of sets of rows. They can be used to collapse and therefore optimize sections of a WHERE clause that can be computed once:

EXPLAIN ANALYZE SELECT * FROM customers WHERE customerid=(SELECT min(customerid) FROM customers)+1;
QUERY PLAN                                                         
----------
Index Scan using customers_pkey on customers  (cost=0.06..8.33 rows=1 width=268) (actual time=0.085..0.088 rows=1 loops=1)
   Index Cond: (customerid = ($1 + 1))
   InitPlan 2 (returns $1)
     ->  Result  (cost=0.05..0.06 rows=1 width=0) (actual time=0.061..0.062 rows=1 loops=1)
           InitPlan 1 (returns $0)
             ->  Limit  (cost...