how_to_begin_transaction.cr

require "pg"

DB.open "postgres://postgres:postgres@localhost:5432/blog_development" do |db|
  db.transaction do |tx|
    conn = tx.connection

    pp conn.scalar "select count(*) from articles" # => 5
    pp conn.exec "insert into articles (title, url, markdown, created_at, updated_at) values ('title', 'url', 'markdown', now(), now())"
    pp db.scalar "select count(*) from articles" # => 5 (because this established another connection)
    pp conn.scalar "select count(*) from articles" # => 6
    tx.rollback
    pp conn.scalar "select count(*) from articles" # => 5 (rollbacked properly)
  end
end