Postgres Database Sequence Resync Rake Task

db.rake

namespace :db do
  namespace :sequences do
    desc 'Brings Postgres database sequences into sync with MAX(id)'
    task sync: :environment do
      ActiveRecord::Base.connection.execute("SET search_path TO public")

      updates = ActiveRecord::Base.connection.select_rows(%Q{
        SELECT 'SELECT setval('''||_schema||'.'||_seq||''', (SELECT MAX('||_column||') FROM '||_schema||'.'||_table||')+1); ' AS updatestring
        FROM (
          SELECT n.nspname AS _schema,
              c.relname AS _table,
              a.attname AS _column,
              SUBSTRING(d.adsrc FROM E'nextval\\\\(''([^'')]+)''') AS _seq
          FROM pg_attrdef       AS d
              JOIN pg_attribute AS a ON a.attrelid = d.adrelid AND a.attnum = d.adnum
              JOIN pg_class     AS c ON c.oid = d.adrelid
              JOIN pg_namespace AS n ON n.oid = c.relnamespace
          WHERE adsrc LIKE 'nextval(''%'
        ) t
      })

      updates.each do |query|
        ActiveRecord::Base.connection.execute(query[0].sub(/\;\s+$/, ''))
      end
    end
  end
end