Index: database/database.4.0.mysql
===================================================================
RCS file: /cvs/drupal/drupal/database/database.4.0.mysql,v
retrieving revision 1.1
diff -u -p -r1.1 database.4.0.mysql
--- database/database.4.0.mysql	10 Apr 2006 13:45:28 -0000	1.1
+++ database/database.4.0.mysql	25 Apr 2006 12:16:23 -0000
@@ -731,7 +731,7 @@ CREATE TABLE users (
   name varchar(60) NOT NULL default '',
   pass varchar(32) NOT NULL default '',
   mail varchar(64) default '',
-  mode tinyint(1) NOT NULL default '0',
+  mode tinyint(1) default NULL,
   sort tinyint(1) default '0',
   threshold tinyint(1) default '0',
   theme varchar(255) NOT NULL default '',
Index: database/database.4.1.mysql
===================================================================
RCS file: /cvs/drupal/drupal/database/database.4.1.mysql,v
retrieving revision 1.1
diff -u -p -r1.1 database.4.1.mysql
--- database/database.4.1.mysql	10 Apr 2006 13:45:28 -0000	1.1
+++ database/database.4.1.mysql	25 Apr 2006 12:16:24 -0000
@@ -782,7 +782,7 @@ CREATE TABLE users (
   name varchar(60) NOT NULL default '',
   pass varchar(32) NOT NULL default '',
   mail varchar(64) default '',
-  mode tinyint(1) NOT NULL default '0',
+  mode tinyint(1) default NULL,
   sort tinyint(1) default '0',
   threshold tinyint(1) default '0',
   theme varchar(255) NOT NULL default '',
Index: database/database.pgsql
===================================================================
RCS file: /cvs/drupal/drupal/database/database.pgsql,v
retrieving revision 1.173
diff -u -p -r1.173 database.pgsql
--- database/database.pgsql	17 Apr 2006 20:48:25 -0000	1.173
+++ database/database.pgsql	25 Apr 2006 12:16:24 -0000
@@ -734,7 +734,7 @@ CREATE TABLE users (
   name varchar(60) NOT NULL default '',
   pass varchar(32) NOT NULL default '',
   mail varchar(64) default '',
-  mode smallint NOT NULL default '0',
+  mode smallint default NULL,
   sort smallint default '0',
   threshold smallint default '0',
   theme varchar(255) NOT NULL default '',
Index: database/updates.inc
===================================================================
RCS file: /cvs/drupal/drupal/database/updates.inc,v
retrieving revision 1.222
diff -u -p -r1.222 updates.inc
--- database/updates.inc	17 Apr 2006 20:48:25 -0000	1.222
+++ database/updates.inc	25 Apr 2006 12:16:27 -0000
@@ -1965,3 +1965,25 @@ function system_update_179() {
 
   return array();
 }
+
+/**
+ * Set the user's comment viewing preference to NULL by default, to distinguish
+ * an unspecified value from a value of 0 (which represents the constant
+ * COMMENT_MODE_FLAT_COLLAPSED).
+ */
+function system_update_180() {
+  $ret = array();
+
+  switch ($GLOBALS['db_type']) {
+    case 'pgsql':
+      db_change_column($ret, 'users', 'mode', 'mode', 'smallint');
+      break;
+    case 'mysql':
+    case 'mysqli':
+      $ret[] = update_sql("ALTER TABLE {users} CHANGE mode mode tinyint(1) default NULL");
+      break;
+  }
+  $ret[] = update_sql("UPDATE {users} SET mode = NULL WHERE mode = 0");
+
+  return $ret;
+}