Understanding simple queries and the cost model

In this section, we will get started with indexes. To show how things work, some test data is needed. The following code snippet shows how data can be created easily:

test=# CREATE TABLE t_test (id serial, name text); 
CREATE TABLE 
test=# INSERT INTO t_test (name) SELECT 'hans'  
   FROM generate_series(1, 2000000); 
INSERT 0 2000000 
test=# INSERT INTO t_test (name) SELECT 'paul'  
   FROM generate_series(1, 2000000); 
INSERT 0 2000000

In the first line, a simple table is created. Two columns are used: an auto increment column, which just keeps creating numbers, and a column that will be filled with static values.

Note

The generate_series function will generate numbers from 1 million to 2 million. So in this example, 2 million static values for hans and 2 million static values for paul are created.

In all, 4 million rows have been added:

test=# SELECT name, count(*) FROM t_test GROUP BY 1; 
 name |  count   
------+--------- 
 hans | 2000000 
...