SQLiteAdapter fails with a dark message when creating columns when inside a transaction

While running some tests which require modifying some fields in a DB table, I ran across a problem that made me lose quite some time. The error I got when running the test (under SQLite3) was:

ActiveRecord::StatementInvalid: SQLite3::SQLException: SQL logic error or missing database: VACUUM

Now, digging into ConnectionAdapters::SQLiteAdapter, I found:

def add_column(table_name, column_name, type, options = {}) #:nodoc:

super(table_name, column_name, type, options)


See last paragraph on http://www.sqlite.org/lang_alter...


execute "VACUUM"

end

Now... Refering to its own documentation, SQLite will fail on vacuums when there is an active transaction (http://www.sqlite.org/lang_vacuu...)... So my tests fail miserably.

I would suggest either of the attached patches.

First version: Try to create the requested column; if it was called in mid-transaction, the DB won't be readable with older versions of MySQL, but it will succeed:

The second possibility is just to disallow adding columns while in a transaction:

Any of them will be better than just leaving the user scratching his head to understand where the error lies :)