title: Using pt-online-schema-change to alter table
body: <p>pt-online-schema-change is not able to alter table. It is failing at the step where it copies rows from the original table to the new table and is throwing the error: copying rows caused a MySQL error 1048:
  Level: warning
  Code: 1048
  Message: column 'trans_datetime' cannot be null</p>
  
  <p>column definition for 'trans_datetime' from show create table >> <code>trans_datetime</code> datetime DEFAULT NULL</p>
  
  <p>which clearly tells that it can have null values. In fact, all the rows in the table which I am trying to alter is having null for 'trans_datetime'</p>
  
  <p>I am running following pt-osc command:</p>
  
  <pre><code>pt-online-schema-change --recursion-method=none --user=test --password=xxxxx 
    --socket=/mysqldata/mysql.sock --nocheck-replication-filters 
    --nocheck-alter --execute 
    --alter "CHANGE COLUMN id id BIGINT(20) NOT NULL, drop primary key, 
             add primary key (order_id, trans_datetime)"
    D=testing,t=temp_test_table
  </code></pre>
  
  <p>Please let me know if you need any more info. Any help on this will be highly appreciated</p>