How to downgrade from Chrome 35 to 34 without losing data?

Question

After upgrading Chromium from 34 to 35, the usability of Chromium went downhill. So I decided to downgrade Chromium. Fortunately, the previous version of Chromium was still somewhere on my disk, so downgrading (in ArchLinux) was as simple as:

sudo pacman -U /var/cache/pacman/pkg/chromium-34.0.1847.137-1-x86_64.pkg.tar.xz

After running the previous command, Chromium did start, but unfortunately, I kept getting bugged by the following message on start-up:

Your profile can not be used because it is from a newer version of Google Chrome. Some features may be unavailable. Please specify a different profile directory or use a newer version of Chrome.

One way to get rid of this message is to delete ~/.config/chromium/Default/Web Data, but this also caused my search engine keywords to disappear.

How can I downgrade Chromium without losing any data?

^{Note: I'm using Linux, but this problem is platform-independent. Feel free to answer from the perspective of a non-Linux operating system such as Windows.}

Answer 1

Note: Close Chrome and back up your profile before messing with it!

Web Data is a SQLite database, so I used the sqlite3 program to open the database.

1. What is the current version of the "Web Data" database? (run SELECT * from meta;)

   sqlite> SELECT * FROM meta;
   Default Search Provider ID|34
   last_compatible_version|55
   version|55
   Builtin Keyword Version|70

2. The emphasized rows in the previous output refer to internal database version numbers in Chromium. For every version, you can find the relevant migration codes in Chromium's source code (autofill_table.cc). Specifically, take a look at the AutofillTable::MigrateToVersion method. Since my database version is 55, I looked at "case 55"

   case 55:
         *update_compatible_version = true;
         return MigrateToVersion55MergeAutofillDatesTable();

   After finding out this method, I was almost ready to write a SQLite query to reverse the migration.

3. Using the knowledge from the previous step (and the original schema from a different table on another computer), I constructed the following query (copy-paste the query to sqlite3):
   Note: This query is specific to downgrading Chrome 35 to 34!

   CREATE TABLE autofill_v54 (
       name VARCHAR,
       value VARCHAR,
       value_lower VARCHAR,
       pair_id INTEGER PRIMARY KEY,
       count INTEGER DEFAULT 1);
   CREATE TABLE autofill_dates (
       pair_id INTEGER DEFAULT 0,
       date_created INTEGER DEFAULT 0);        
   
   INSERT INTO autofill_v54 (
       name,
       value,
       value_lower,
       count
   ) SELECT name, value, value_lower, count FROM autofill;
   
   INSERT INTO autofill_dates (
       pair_id,
       date_created
   ) SELECT pair_id, date_created
     FROM autofill_v54 a54 JOIN autofill a USING (name, value);
   
   DROP TABLE autofill;
   ALTER TABLE autofill_v54 RENAME TO autofill;
   
   CREATE INDEX autofill_name ON autofill (name);
   CREATE INDEX autofill_name_value_lower ON autofill (name, value_lower);
   

4. After reverting the migration, you can safely lower the database version:

   UPDATE meta SET value='54' WHERE key='version' OR
                                    key = 'last_compatible_version';
   

5. Close the database using .quit

After completing all of these steps, I started Chromium, there were no annoying popups and all profile data was still intact!

Answer 2

I confirm: the solution with sqlite3 works fine !

I'm an Ubuntu user (14.04), but I tried this method not with chromium but with google-chrome-stable.

I've downgraded chrome from 35 to 34 because there is no way for running java applet in the release 35. :-(

sudo apt-get purge google-chrome-stable
sudo rm -f /etc/apt/sources.list.d/google-chrome.list*
sudo apt-get update
cd ~/Downloads
wget http://95.31.35.30/chrome/pool/main/g/google-chrome-stable/google-chrome-stable_34.0.1847.137-1_amd64.deb

By removing this source, google-chrome will no longer update automatically. I have installed the release 34 from nautilus with gdebi. You can install gdebi with:

sudo apt-get install gdebi

The problem starts here... Message = 'Your profile can not be used because it is from a newer...'
You can install sqlite3 like this:

sudo apt-get install sqlite3

to execute the solution above (provided by Rob W), do:

cd ~/.config/google-chrome/Default
sqlite3 Web\ Data

After that, simply copy/paste the steps 1, 3, 4, 5 given by Rob W.
Hope this help. ;-)