diff --git a/resources/sql/autopatches/20190215.daemons.01.dropdataid.php b/resources/sql/autopatches/20190215.daemons.01.dropdataid.php
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20190215.daemons.01.dropdataid.php
@@ -0,0 +1,21 @@
+<?php
+
+// See T6615. We're about to change the nullability on the "dataID" column,
+// but it may have a UNIQUE KEY on it. Make sure we get rid of this key first
+// so we don't run into trouble.
+
+// There's no "IF EXISTS" modifier for "ALTER TABLE" so run this as a PHP patch
+// instead of an SQL patch.
+
+$table = new PhabricatorWorkerActiveTask();
+$conn = $table->establishConnection('w');
+
+try {
+  queryfx(
+    $conn,
+    'ALTER TABLE %R DROP KEY %T',
+    $table,
+    'dataID');
+} catch (AphrontQueryException $ex) {
+  // Ignore.
+}
diff --git a/resources/sql/autopatches/20190215.daemons.02.nulldataid.sql b/resources/sql/autopatches/20190215.daemons.02.nulldataid.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20190215.daemons.02.nulldataid.sql
@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_worker.worker_activetask
+  CHANGE dataID dataID INT UNSIGNED NOT NULL;
diff --git a/src/infrastructure/daemon/workers/storage/PhabricatorWorkerActiveTask.php b/src/infrastructure/daemon/workers/storage/PhabricatorWorkerActiveTask.php
--- a/src/infrastructure/daemon/workers/storage/PhabricatorWorkerActiveTask.php
+++ b/src/infrastructure/daemon/workers/storage/PhabricatorWorkerActiveTask.php
@@ -14,35 +14,21 @@
       self::CONFIG_IDS => self::IDS_COUNTER,
       self::CONFIG_TIMESTAMPS => false,
       self::CONFIG_KEY_SCHEMA => array(
-        'dataID' => array(
-          'columns' => array('dataID'),
-          'unique' => true,
-        ),
         'taskClass' => array(
           'columns' => array('taskClass'),
         ),
         'leaseExpires' => array(
           'columns' => array('leaseExpires'),
         ),
-        'leaseOwner' => array(
-          'columns' => array('leaseOwner(16)'),
-        ),
         'key_failuretime' => array(
           'columns' => array('failureTime'),
         ),
-        'leaseOwner_2' => array(
+        'key_owner' => array(
           'columns' => array('leaseOwner', 'priority', 'id'),
         ),
       ) + $parent[self::CONFIG_KEY_SCHEMA],
     );
 
-    $config[self::CONFIG_COLUMN_SCHEMA] = array(
-      // T6203/NULLABILITY
-      // This isn't nullable in the archive table, so at a minimum these
-      // should be the same.
-      'dataID' => 'uint32?',
-    ) + $parent[self::CONFIG_COLUMN_SCHEMA];
-
     return $config + $parent;
   }
 
@@ -74,7 +60,7 @@
       $this->failureCount = 0;
     }
 
-    if ($is_new && ($this->getData() !== null)) {
+    if ($is_new) {
       $data = new PhabricatorWorkerTaskData();
       $data->setData($this->getData());
       $data->save();
diff --git a/src/infrastructure/daemon/workers/storage/PhabricatorWorkerArchiveTask.php b/src/infrastructure/daemon/workers/storage/PhabricatorWorkerArchiveTask.php
--- a/src/infrastructure/daemon/workers/storage/PhabricatorWorkerArchiveTask.php
+++ b/src/infrastructure/daemon/workers/storage/PhabricatorWorkerArchiveTask.php
@@ -28,9 +28,6 @@
       'dateCreated' => array(
         'columns' => array('dateCreated'),
       ),
-      'leaseOwner' => array(
-        'columns' => array('leaseOwner', 'priority', 'id'),
-      ),
       'key_modified' => array(
         'columns' => array('dateModified'),
       ),