Index: lib/db/upgrade.php
===================================================================
RCS file: /cvsroot/moodle/moodle/lib/db/upgrade.php,v
retrieving revision 1.480
diff -u -r1.480 upgrade.php
--- lib/db/upgrade.php	13 Sep 2010 13:01:34 -0000	1.480
+++ lib/db/upgrade.php	15 Sep 2010 09:48:56 -0000
@@ -5082,7 +5082,24 @@
         upgrade_main_savepoint(true, 2010082502);
     }
 
-    if ($oldversion < 2010091300) {
+    if ($oldversion < 2010091500) {
+        // This index used to exist in Moodle 1.9 and was never dropped in the upgrade above.
+        // Drop it now, or it breaks the following alter column.
+
+        // Define index parentcontextid-showinsubcontexts-pagetypepattern-subpagepattern (not unique) to be dropped form block_instances
+        $table = new xmldb_table('block_instances');
+        $index = new xmldb_index('pagetypepattern', XMLDB_INDEX_NOTUNIQUE, array('pagetypepattern'));
+
+        // Conditionally launch drop index parentcontextid-showinsubcontexts-pagetypepattern-subpagepattern
+        if ($dbman->index_exists($table, $index)) {
+            $dbman->drop_index($table, $index);
+        }
+
+        // Main savepoint reached
+        upgrade_main_savepoint(true, 2010091500);
+    }
+
+    if ($oldversion < 2010091501) {
         // Need to drop the index before we can alter the column precision in the next step.
 
         // Define index parentcontextid-showinsubcontexts-pagetypepattern-subpagepattern (not unique) to be dropped form block_instances
@@ -5095,10 +5112,10 @@
         }
 
         // Main savepoint reached
-        upgrade_main_savepoint(true, 2010091300);
+        upgrade_main_savepoint(true, 2010091501);
     }
 
-    if ($oldversion < 2010091301) {
+    if ($oldversion < 2010091502) {
 
         // Changing precision of field pagetypepattern on table block_instances to (64)
         $table = new xmldb_table('block_instances');
@@ -5108,10 +5125,10 @@
         $dbman->change_field_precision($table, $field);
 
         // Main savepoint reached
-        upgrade_main_savepoint(true, 2010091301);
+        upgrade_main_savepoint(true, 2010091502);
     }
 
-    if ($oldversion < 2010091302) {
+    if ($oldversion < 2010091503) {
         // Now add the index back.
 
         // Define index parentcontextid-showinsubcontexts-pagetypepattern-subpagepattern (not unique) to be added to block_instances
@@ -5124,7 +5141,7 @@
         }
 
         // Main savepoint reached
-        upgrade_main_savepoint(true, 2010091302);
+        upgrade_main_savepoint(true, 2010091503);
     }
 
     return true;
Index: version.php
===================================================================
RCS file: /cvsroot/moodle/moodle/version.php,v
retrieving revision 1.1750
diff -u -r1.1750 version.php
--- version.php	13 Sep 2010 13:01:35 -0000	1.1750
+++ version.php	15 Sep 2010 09:48:55 -0000
@@ -29,7 +29,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$version = 2010091302;  // YYYYMMDD   = date of the last version bump
+$version = 2010091503;  // YYYYMMDD   = date of the last version bump
                         //         XX = daily increments
 
 $release = '2.0 Preview 4+ (Build: 20100913)';  // Human-friendly version name