Add building of updates table data.

                    };

                }

            });

            // For completeness I should also add users from updates,

            // but it turns out that everybody who has edited comments

            // has also posted them too.  So I skip this part.

        });

        return usersMap;

    };

})();

var UpdatesTable = (function() {

    function extract(data, next) {

        var updates = [];

        data.mongo_comments.forEach(function(c) {

            c.updates.forEach(function(u) {

                updates.push({

                    user_id: data.usersMap[u.author].id,

                    comment_id: data.commentsMap[CommentsTable.buildKey(c)].id,

                    action: u.action || 'update',

                    created_at: u.updatedAt

                });

            });

        });

        addIds(updates);

        data.updates = updates;

        next();

    }

    return {

        extract: extract

    };

})();

// Calls an array of functions in sequence passing to each function

// the data argument and a function to call when it finishes.

function sequence(data, callbacks) {

        TargetsTable.extract,

        CommentsTable.extract,

        VotesTable.extract,

        UpdatesTable.extract,

        function(data, next) {

            console.log(data.users.length + " users");

            console.log(data.targets.length + " targets");

            console.log(data.comments.length + " comments");

            console.log(data.votes.length + " votes");

            console.log(data.updates.length + " updates");

            process.exit();

        }

    ]);