More Rails Progress

I've been playing with Rails over the past few days and want to quickly express my experience so far.

Creating joins, lookup tables, tuning, grouping, sorting, and setting limits are all easy. You can do something like:

Actor.sum(:appearances,
:joins => "INNER JOIN appearances_show_lookup asl
           ON asl.appearances_id
             = appearances.appearances_id",
:group=>'asl.appearances_id',
:order=>'sum(appearances) DESC', :limit=>10)

which translates into

SELECT m.appearances_id, sum(appearances)
FROM appearances m
INNER JOIN appearances_show_lookup md
  ON md.appearances_id=m.appearances_id
GROUP BY m.appearances_id
ORDER BY sum(appearances) DESC
LIMIT 10;

or...

Actor.find(:all,include=>:appearances_type,
:conditions=>"appearances_type.name='guest'",
:limit=>10)

to

SELECT *
FROM appearances
LEFT OUTER JOIN appearances_type
  ON appearances_type.appearances_type_id =
     appearances.appearances_type_id
WHERE (appearances_type.name='guest')
LIMIT 10

or expand it to 3 tables...

Actor.find(:all,
:include=>[:appearances_type, :show_scores],
:conditions=>"appearances_type.name='guest'",
:limit=>10,
:group=>'appearances.appearances_id' )

to

SELECT DISTINCT appearances.appearances_id
FROM appearances
LEFT OUTER JOIN appearances_type
  ON appearances_type.appearances_type_id
    = appearances.appearances_type_id
LEFT OUTER JOIN appearances_show_lookup
  ON appearances_show_lookup.appearances_id
    = appearances.appearances_id
WHERE (appearances_type.name='guest')  LIMIT 10

SELECT *
FROM appearances
LEFT OUTER JOIN appearances_type
  ON appearances_type.appearances_type_id
    = appearances.appearances_type_id
LEFT OUTER JOIN appearances_show_lookup
  ON appearances_show_lookup.appearances_id
    = appearances.appearances_id
WHERE (appearances_type.name='guest')
AND appearances.appearances_id
    IN ('5', '6', '7', '8', '9', '10',
        '11', '12', '13', '14')
GROUP BY appearances.appearances_id

Since this final Ruby/Rails code actually produces 2 queries (and I'd prefer an inner join to an outer join as the default), I'm going to opt to create my own queries using find_by_sql like this...

Actor.find_by_sql "
  SELECT m.*,
    SUM(md.appearances) appearances,
    mt.name type_name
  FROM appearances m
    INNER JOIN appearances_type mt
    ON m.appearances_type_id
      = mt.appearances_type_id
    INNER JOIN appearances_show_lookup md
    ON md.appearances_id
      = m.appearances_id
  WHERE mt.nominal = false
  GROUP by m.appearances_id
  ORDER BY appearances desc
  LIMIT 10"

and produces identical SQL.

Even though you can override defaults for table names, primary keys and the like, I can't get the scaffolding scripts to work unless I set them to the Rails defaults (opinionated software!). I'm going to try and use the Rails Migrations tool for these updates. I'll be sure to provide updates on my progress.

Like many others, I love what I've experienced in Rails so far. It's a breath of fresh air from my previous Hibernate and Java experience. I love the ability to make a change then instantly test it using the Ruby console. It's really great! Now my concerns are shifting to performance and scalability.