title: Ignore items in Liquibase diff
body: <p>We have an in-house tool that compares Hibernate's view of our application to the Liquibase changelog that manages the database.  This is using Liquibase 3.3.1, which has discovered database difference Liquibase 2.x did not see, and which we would prefer to ignore. We already ignore all views in the comparison: </p>
  
  <pre><code>    CompareControl control = new CompareControl();
      control.getComparedTypes().remove(View.class);
      DiffResult result = liquibase.diff(reference, target, control);
      DiffOutputControl output = new DiffOutputControl(false, false, false);
      DiffToChangeLog changeLog = new DiffToChangeLog(result, output);
  </code></pre>
  
  <p>The other comparisons we would like to ignore are:</p>
  
  <p>Default values. When adding columns to the database we use default values which Hibernate is unaware of:</p>
  
  <pre><code>&lt;changeSet author="adrian (generated)" id="1419421913188-163"&gt;
      &lt;dropDefaultValue columnDataType="timestamp(29,6)" columnName="timestamp" tableName="transportjob"/&gt;
  &lt;/changeSet&gt;
  </code></pre>
  
  <p>Foreign key constraints. We change some foreign key constraints to <code>CASCADE</code>. (This is the exact opposite problem to <a href="https://stackoverflow.com/questions/16166864/liquibase-diff-tool-missing-constraints">Liquibase Diff Tool missing constraints</a>).</p>
  
  <pre><code>&lt;changeSet author="adrian (generated)" id="1419421913188-90"&gt;
      &lt;dropForeignKeyConstraint baseTableName="site" constraintName="fk_rpietmexbx0ywmlywidira71h"/&gt;
      &lt;addForeignKeyConstraint baseColumnNames="logo_id" baseTableName="site" constraintName="fk_rpietmexbx0ywmlywidira71h" referencedColumnNames="id" referencedTableName="image"/&gt;
  &lt;/changeSet&gt;
  </code></pre>