Connection Object
=================

PgInterface and TdsInterface both take a connection Hash, which is all very
well, but it means that we are running one database connection per model.
Presumably this is a bad idea. :-)

This actually hasn't come up in my own use of Pod4 -- for complex reasons I'm
either using SequelInterface or running transient jobs which start up a couple
of models, do some work, and then stop entirely -- but it _is_ rather silly.

Connection is baked into those interfaces, and interface dependant. So I'm
thinking in terms of a memoising object that stores the connection hash and
then gets passed to the interface. When the interface wants a connection, then
it asks the connection object. If the connection object doesn't have one, then
the interface connects, and gives the connection to the connection object.


Transactions
============

We really need this, because without it we can't even pretend to be doing
proper pessimistic locking.

I've got a pretty solid idea for a nice, simple way to make this happen. It
will be in place soon.


Migrations
==========

This will almost certainly be something crude -- since we don't really control
the database connection in the same way as, say, ActiveRecord -- but I honestly
think it's a worthwhile feature.  Just having something that you can version
control and run to update a data model is enough, really.

I'm not yet sure of the least useless way to implement it.  Again, I favour SQL
as the DSL.


JDBC-SQL interface
==================

For the jdbc-msssqlserver gem.  Doable ... I *think*.

    driver = Java::com.microsoft.sqlserver.jdbc.SQLServerDriver.new
    props = java.util.Properties.new
    props.setProperty("user", "username")
    props.setProperty("password", "password")
    url = 'jdbc:sqlserver://servername;instanceName=instance;databaseName=DbName;'

    conn = driver.connect(url, props)
    #or maybe conn = driver.get_connection(url, "username", "password")

    stmt = conn.create_statement
    sql = %Q|blah;|

    rsS = stmt.execute_query(sql)

    while (rsS.next) do
      veg = Hash.new
      veg["vegName"] = rsS.getObject("name")
      # etc
    end

    stmt.close
    conn.close

    see https://github.com/jruby/jruby/wiki/JDBC