[ci skip] Add upgrade instructions for CI_Sessions

1 files changed, 26 insertions, 0 deletions

diff --git a/user_guide_src/source/installation/upgrade_312.rst b/user_guide_src/source/installation/upgrade_312.rst
index 91467233e..e0b2191dd 100644
--- a/user_guide_src/source/installation/upgrade_312.rst
+++ b/user_guide_src/source/installation/upgrade_312.rst
@@ -12,3 +12,29 @@ 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);