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+#############################
+Upgrading from 3.1.1 to 3.1.2
+#############################
+
+Before performing an update you should take your site offline by
+replacing the index.php file with a static one.
+
+Step 1: Update your CodeIgniter files
+=====================================
+
+Replace all files and directories in your *system/* directory.
+
+.. note:: If you have any custom developed files in these directories,
+	please make copies of them first.
+
+Step 2: Update your "ci_sessions" database table
+================================================
+
+If you're using the :doc:`Session Library </libraries/sessions>` with the
+'database' driver, you may have to ``ALTER`` your sessions table for your
+sessions to continue to work.
+
+.. note:: The table in question is not necessarily named "ci_sessions".
+	It is what you've set as your ``$config['sess_save_path']``.
+
+This will only affect you if you've changed your ``session.hash_function``
+*php.ini* setting to something like 'sha512'. Or if you've been running
+an older CodeIgniter version on PHP 7.1+.
+
+It is recommended that you do this anyway, just to avoid potential issues
+in the future if you do change your configuration.
+
+Just execute the one of the following SQL queries, depending on your
+database::
+
+	// MySQL:
+	ALTER TABLE ci_sessions CHANGE id id varchar(128) NOT NULL;
+
+	// PostgreSQL
+	ALTER TABLE ci_sessions ALTER COLUMN id SET DATA TYPE varchar(128);