1 files changed, 74 insertions, 1 deletions
diff --git a/spec/support/db_cleaner.rb b/spec/support/db_cleaner.rb
index 940ff2751d3..316d645f99f 100644
--- a/spec/support/db_cleaner.rb
+++ b/spec/support/db_cleaner.rb
@@ -2,7 +2,7 @@
 
 module DbCleaner
   def all_connection_classes
-    ::ActiveRecord::Base.connection_handler.connection_pool_names.map(&:constantize)
+    ::BeforeAllAdapter.all_connection_classes
   end
 
   def delete_from_all_tables!(except: [])
@@ -20,6 +20,79 @@ module DbCleaner
       DatabaseCleaner[:active_record, { connection: connection_class }]
     end
   end
+
+  def any_connection_class_with_more_than_allowed_columns?
+    all_connection_classes.any? do |connection_class|
+      more_than_allowed_columns?(connection_class)
+    end
+  end
+
+  def more_than_allowed_columns?(connection_class)
+    # Postgres maximum number of columns in a table is 1600 (https://github.com/postgres/postgres/blob/de41869b64d57160f58852eab20a27f248188135/src/include/access/htup_details.h#L23-L47).
+    # And since:
+    # "The DROP COLUMN form does not physically remove the column, but simply makes
+    # it invisible to SQL operations. Subsequent insert and update operations in the
+    # table will store a null value for the column. Thus, dropping a column is quick
+    # but it will not immediately reduce the on-disk size of your table, as the space
+    # occupied by the dropped column is not reclaimed.
+    # The space will be reclaimed over time as existing rows are updated."
+    # according to https://www.postgresql.org/docs/current/sql-altertable.html.
+    # We drop and recreate the database if any table has more than 1200 columns, just to be safe.
+    max_allowed_columns = 1200
+    tables_with_more_than_allowed_columns = connection_class.connection.execute(<<-SQL)
+      SELECT attrelid::regclass::text AS table, COUNT(*) AS column_count
+        FROM pg_attribute
+        GROUP BY attrelid
+        HAVING COUNT(*) > #{max_allowed_columns}
+    SQL
+
+    tables_with_more_than_allowed_columns.each do |result|
+      puts "The #{result['table']} (#{connection_class.connection_db_config.name}) table has #{result['column_count']} columns."
+    end
+
+    tables_with_more_than_allowed_columns.any?
+  end
+
+  def recreate_all_databases!
+    start = Gitlab::Metrics::System.monotonic_time
+
+    puts "Recreating the database"
+
+    force_disconnect_all_connections!
+
+    ActiveRecord::Tasks::DatabaseTasks.drop_current
+    ActiveRecord::Tasks::DatabaseTasks.create_current
+    ActiveRecord::Tasks::DatabaseTasks.load_schema_current
+
+    # Migrate each database individually
+    with_reestablished_active_record_base do
+      all_connection_classes.each do |connection_class|
+        ActiveRecord::Base.establish_connection(connection_class.connection_db_config)
+
+        ActiveRecord::Tasks::DatabaseTasks.migrate
+      end
+    end
+
+    puts "Databases re-creation done in #{Gitlab::Metrics::System.monotonic_time - start}"
+  end
+
+  def force_disconnect_all_connections!
+    all_connection_classes.each do |connection_class|
+      # We use `connection_pool` to avoid going through
+      # Load Balancer since it does retry ops
+      pool = connection_class.connection_pool
+
+      # Force disconnect https://www.cybertec-postgresql.com/en/terminating-database-connections-in-postgresql/
+      pool.connection.execute(<<-SQL)
+        SELECT pg_terminate_backend(pid)
+          FROM pg_stat_activity
+          WHERE datname = #{pool.connection.quote(pool.db_config.database)}
+            AND pid != pg_backend_pid();
+      SQL
+
+      connection_class.connection_pool.disconnect!
+    end
+  end
 end
 
 DbCleaner.prepend_mod_with('DbCleaner')