title: Why does PostgreSQL perform sequential scan on indexed column?
body: <p>Very simple example - one table, one index, one query:</p>
  
  <pre><code>CREATE TABLE book
  (
    id bigserial NOT NULL,
    "year" integer,
    -- other columns...
  );
  
  CREATE INDEX book_year_idx ON book (year)
  
  EXPLAIN
   SELECT *
     FROM book b
    WHERE b.year &gt; 2009
  </code></pre>
  
  <p>gives me:</p>
  
  <pre><code>Seq Scan on book b  (cost=0.00..25663.80 rows=105425 width=622)
    Filter: (year &gt; 2009)
  </code></pre>
  
  <p>Why it does NOT perform index scan instead?
  What am I missing?</p>