title: ERROR: data type tstzrange[] has no default operator class for access method "gist" in Postgres 10
body: <p>I am trying to set an index to a <code>tstzrange[]</code> column in PostgreSQL 10. I created the column via the pgAdmin 4 GUI, set its name and data type as <code>tstzrange[]</code> and set it as <code>not null</code>, nothing more.</p>
  
  <p>I then did a <code>CREATE EXTENSION btree_gist;</code> for the database and it worked.</p>
  
  <p>Then I saw in the <a href="https://www.postgresql.org/docs/10/static/rangetypes.html#RANGETYPES-INDEXING" rel="nofollow noreferrer">documentation</a> that I should index the range and I do:</p>
  
  <pre><code>CREATE INDEX era_ac_range_idx ON era_ac USING GIST (era_ac_range);
  </code></pre>
  
  <p>...but then I get:</p>
  
  <blockquote>
    <p>ERROR:  data type tstzrange[] has no default operator class for
    access method "gist"</p>
  </blockquote>
  
  <p>which, frankly, I don't know what it actually means, or how to solve it. What should I do ? </p>
  
  <p>PS, that column is currently empty, has no data yet.</p>
  
  <p>Ps2, This table describes chronological eras, there is an id, the era name (eg the sixties) and the timezone range (eg 1960-1969). 
  A date is inserted by the user and I want to check in which era it belongs.</p>