diff --git a/classes/File.php b/classes/File.php
index ce2f940161..dad54166b1 100644
--- a/classes/File.php
+++ b/classes/File.php
@@ -26,7 +26,8 @@ class File extends Managed_DataObject
 {
     public $__table = 'file';                            // table name
     public $id;                              // int(4)  primary_key not_null
-    public $url;                             // varchar(255)  unique_key
+    public $urlhash;                         // varchar(64)  unique_key
+    public $url;                             // text
     public $mimetype;                        // varchar(50)
     public $size;                            // int(4)
     public $title;                           // varchar(255)
@@ -37,12 +38,15 @@ class File extends Managed_DataObject
     public $height;                          // int(4)
     public $modified;                        // timestamp()   not_null default_CURRENT_TIMESTAMP
 
+    const URLHASH_ALG = 'sha256';
+
     public static function schemaDef()
     {
         return array(
             'fields' => array(
                 'id' => array('type' => 'serial', 'not null' => true),
-                'url' => array('type' => 'varchar', 'length' => 255, 'description' => 'destination URL after following redirections'),
+                'urlhash' => array('type' => 'varchar', 'length' => 64, 'description' => 'sha256 of destination URL (url field)'),
+                'url' => array('type' => 'text', 'description' => 'destination URL after following redirections'),
                 'mimetype' => array('type' => 'varchar', 'length' => 50, 'description' => 'mime type of resource'),
                 'size' => array('type' => 'int', 'description' => 'size of resource when available'),
                 'title' => array('type' => 'varchar', 'length' => 255, 'description' => 'title of resource when available'),
@@ -56,7 +60,7 @@ class File extends Managed_DataObject
             ),
             'primary key' => array('id'),
             'unique keys' => array(
-                'file_url_key' => array('url'),
+                'file_urlhash_key' => array('urlhash'),
             ),
         );
     }
@@ -77,10 +81,11 @@ class File extends Managed_DataObject
         // I don't know why we have to keep doing this but I'm adding this last check to avoid
         // uniqueness bugs.
 
-        $file = File::getKV('url', $given_url);
+        $file = File::getKV('urlhash', self::hashurl($given_url));
         
         if (!$file instanceof File) {
             $file = new File;
+            $file->urlhash = self::hashurl($given_url);
             $file->url = $given_url;
             if (!empty($redir_data['protected'])) $file->protected = $redir_data['protected'];
             if (!empty($redir_data['title'])) $file->title = $redir_data['title'];
@@ -462,7 +467,7 @@ class File extends Managed_DataObject
         if (!empty($this->filename)) {
             // A locally stored file, so let's generate a URL for our instance.
             $url = self::url($this->filename);
-            if ($url != $this->url) {
+            if (self::urlhash($url) !== $this->urlhash) {
                 // For indexing purposes, in case we do a lookup on the 'url' field.
                 // also we're fixing possible changes from http to https, or paths
                 $this->updateUrl($url);
@@ -476,14 +481,15 @@ class File extends Managed_DataObject
 
     public function updateUrl($url)
     {
-        $file = File::getKV('url', $url);
+        $file = File::getKV('urlhash', self::hashurl($url));
         if ($file instanceof File) {
             throw new ServerException('URL already exists in DB');
         }
-        $sql = 'UPDATE %1$s SET url=%2$s WHERE url=%3$s;';
+        $sql = 'UPDATE %1$s SET urlhash=%2$s, url=%3$s WHERE urlhash=%4$s;';
         $result = $this->query(sprintf($sql, $this->__table,
+                                             $this->_quote((string)self::hashurl($url)),
                                              $this->_quote((string)$url),
-                                             $this->_quote((string)$this->url)));
+                                             $this->_quote((string)$this->urlhash)));
         if ($result === false) {
             common_log_db_error($this, 'UPDATE', __FILE__);
             throw new ServerException("Could not UPDATE {$this->__table}.url");
@@ -502,9 +508,9 @@ class File extends Managed_DataObject
 
     function blowCache($last=false)
     {
-        self::blow('file:notice-ids:%s', $this->url);
+        self::blow('file:notice-ids:%s', $this->urlhash);
         if ($last) {
-            self::blow('file:notice-ids:%s;last', $this->url);
+            self::blow('file:notice-ids:%s;last', $this->urlhash);
         }
         self::blow('file:notice-count:%d', $this->id);
     }
@@ -582,4 +588,12 @@ class File extends Managed_DataObject
 
         return $title ?: null;
     }
+
+    static public function hashurl($url)
+    {
+        if (empty($url)) {
+            throw new Exception('No URL provided to hash algorithm.');
+        }
+        return hash(self::URLHASH_ALG, $url);
+    }
 }
diff --git a/scripts/upgrade.php b/scripts/upgrade.php
index c221a495af..eeddf5559f 100644
--- a/scripts/upgrade.php
+++ b/scripts/upgrade.php
@@ -76,6 +76,7 @@ function updateSchemaCore()
     $schema = Schema::get();
     $schemaUpdater = new SchemaUpdater($schema);
     foreach (tableDefs() as $table => $def) {
+        preAlterFixes($schemaUpdater, $table);
         $schemaUpdater->register($table, $def);
     }
     $schemaUpdater->checkSchema();
@@ -83,6 +84,40 @@ function updateSchemaCore()
     printfnq("DONE.\n");
 }
 
+function preAlterFixes($schemaUpdater, $table)
+{
+    switch ($table) {
+    case 'file':
+        $schemadef = $schemaUpdater->schema->getTableDef($table);
+        if (isset($schemadef['fields']['urlhash'])) {
+            // We already have the urlhash field, so no need to migrate it.
+            break;
+        }
+        printfnq("\nFound old $table table, upgrading it to contain 'urlhash' field...\n");
+        // We have to create a urlhash that is _not_ the primary key,
+        // transfer data and THEN run checkSchema
+        $schemadef['fields']['urlhash'] = array (
+                                              'type' => 'varchar',
+                                              'length' => 64,
+                                              'description' => 'sha256 of destination URL after following redirections',
+                                            );
+        $schemaUpdater->schema->ensureTable($table, $schemadef);
+        printfnq("DONE.\n");
+
+        $filefix = new File();
+        // urlhash is hash('sha256', $url) in the File table
+        printfnq("Updating urlhash fields in $table table...\n");
+        $filefix->query(sprintf('UPDATE %1$s SET %2$s=%3$s;',
+                            $schemaUpdater->schema->quoteIdentifier($table),
+                            'urlhash',
+                            // The line below is "result of sha256 on column `url`"
+                            'SHA2(url, 256)'));
+        printfnq("DONE.\n");
+        printfnq("Resuming core schema upgrade...");
+        break;
+    }
+}
+
 function updateSchemaPlugins()
 {
     printfnq("Upgrading plugin schema...");