Postgres Arrays are One-Based

Today I was reminded that Postgres arrays are one-based. This realization came while using Ruby's times method (zero-based index) to generate SQL targeting a Postgres array (one-based index).

Take this table:

 name  |      pay_by_quarter
-------+---------------------------
 Bill  | {10000,10000,10000,10000}
 Carol | {20000,25000,25000,25000}
(2 rows)

To select the first-quarter pay for all employees, use index 1.

my_database=# select pay_by_quarter[1] from sal_emp;
 pay_by_quarter
----------------
          10000
          20000
(2 rows)

Using your first Ruby index value 0 to produce pay_by_quarter[0] returns a sad, empty column.

http://www.postgresql.org/docs/current/static/arrays.html