title: How can I force Liquibase to recalculate checksums without re-running the statements?
body: <p>We're using Liquibase 3.2 with Java 6.  Is there a way I can force Liquibase to recalculate checksums without re-running the same statements from our Liquibase files?  In our database, I run this ...</p>
  
  <pre><code>update DATABASECHANGELOG set md5sum = null where 1;
  </code></pre>
  
  <p>However, when I run my Liquibase change scripts, certain executions still fail with the following errors ...</p>
  
  <pre><code>invoking liquibase change script with file /tmp/deploywork/db.changelog-master.xml
  running /usr/java/liquibase/liquibase  --logLevel=info --driver=com.mysql.jdbc.Driver --classpath=/usr/java/jboss/modules/com/mysql/main/mysql-connector-java-5.1.22-bin.jar --changeLogFile=/tmp/deploywork/db.changelog-master.xml --url="jdbc:mysql://myservername:3306/my_db" --username=username --password=password update 
  INFO 5/13/15 2:15 PM: liquibase: Successfully acquired change log lock
  INFO 5/13/15 2:15 PM: liquibase: Reading from my_db.DATABASECHANGELOG
  INFO 5/13/15 2:15 PM: liquibase: Successfully released change log lock
  Unexpected error running Liquibase: Validation Failed:
       3 change sets check sum
            db.changelog-1.0.xml::1357593229391-25::rob (generated) is now: 7:5cfe9ecd779a71b6287ef2360a6979bf
            db.changelog-7.0.xml::create-address-email-index::davea is now: 7:da0132e30ebd6a1bc52d9a39bb8c56d7
            db.changelog-7.0.xml::add-myproject-event-object-id-col::davea is now: 7:2eab5d784647ce33ef3488aa8c383443
  
  
  SEVERE 5/13/15 2:15 PM: liquibase: Validation Failed:
       3 change sets check sum
            db.changelog-1.0.xml::1357593229391-25::rob (generated) is now: 7:5cfe9ecd779a71b6287ef2360a6979bf
            db.changelog-7.0.xml::create-address-email-index::davea is now: 7:da0132e30ebd6a1bc52d9a39bb8c56d7
            db.changelog-7.0.xml::add-myproject-event-object-id-col::davea is now: 7:2eab5d784647ce33ef3488aa8c383443
  
  liquibase.exception.ValidationFailedException: Validation Failed:
       3 change sets check sum
            db.changelog-1.0.xml::1357593229391-25::rob (generated) is now: 7:5cfe9ecd779a71b6287ef2360a6979bf
            db.changelog-7.0.xml::create-address-email-index::davea is now: 7:da0132e30ebd6a1bc52d9a39bb8c56d7
            db.changelog-7.0.xml::add-myproject-event-object-id-col::davea is now: 7:2eab5d784647ce33ef3488aa8c383443
  
      at liquibase.changelog.DatabaseChangeLog.validate(DatabaseChangeLog.java:181)
      at liquibase.Liquibase.update(Liquibase.java:191)
      at liquibase.Liquibase.update(Liquibase.java:174)
      at liquibase.integration.commandline.Main.doMigration(Main.java:997)
      at liquibase.integration.commandline.Main.run(Main.java:170)
      at liquibase.integration.commandline.Main.main(Main.java:89)
  </code></pre>
  
  <p>Here is one of the change sets that the script is complaining about …</p>
  
  <pre><code>    &lt;changeSet author="davea" id="add-myproject-event-object-id-col"&gt;
          &lt;addColumn tableName="sb_myproject_event"&gt;
              &lt;column name="OBJECT_ID" type="VARCHAR(32)"/&gt;
          &lt;/addColumn&gt;
          &lt;createIndex indexName="SB_myproject_EVENT_IDX"
              tableName="sb_myproject_event"
              unique="false"&gt;
              &lt;column name="OBJECT_ID" type="varchar(32)" /&gt;
          &lt;/createIndex&gt;
          &lt;sql&gt;update sb_myproject_event set object_id=LEFT(SUBSTRING_INDEX(event_data, '&amp;quot;id&amp;quot;:&amp;quot;', -2), 24) where object_id is null and event_data is not null;&lt;/sql&gt;
          &lt;!--  Delete older events that no longer need to be processed --&gt;
          &lt;sql&gt;delete from sb_myproject_event where id not in (select q.* from (select e.id FROM sb_myproject_event e, (select object_id, max(date_processed) d from sb_myproject_event group by object_id) o where e.object_id = o.object_id and e.date_processed = o.d) q);&lt;/sql&gt;
      &lt;/changeSet&gt;
  </code></pre>
  
  <p>As I said, I only want to recalculate checksums (have to do this because we're changing Liquibase versions).</p>