Module: Squeel::Adapters::ActiveRecord::RelationExtensions

Defined in:
lib/squeel/adapters/active_record/relation_extensions.rb,
lib/squeel/adapters/active_record/3.0/relation_extensions.rb,
lib/squeel/adapters/active_record/3.1/relation_extensions.rb

Constant Summary collapse

JoinAssociation = 
::ActiveRecord::Associations::JoinDependency::JoinAssociation
JoinDependency = 
::ActiveRecord::Associations::JoinDependency

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#join_dependency ⇒ Object

Returns a JoinDependency for the current relation.

We don’t need to clear out @join_dependency by overriding #reset, because the default #reset already does this, despite never setting it anywhere that I can find. Serendipity, I say!



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 19

def join_dependency
  @join_dependency ||= (build_join_dependency(table, @joins_values) && @join_dependency)
end

Class Method Details

.included(base) ⇒ Object

ZOMG ALIAS_METHOD_CHAIN IS BELOW. HIDE YOUR EYES! … … … Since you’re still looking, let me explain this horrible transgression you see before you.

You see, Relation#where_values_hash and with_default_scope are defined on the ActiveRecord::Relation class, itself. ActiveRecord::Relation class. Since they’re defined there, but I would very much like to modify their behavior, I have three choices.

  1. Inherit from ActiveRecord::Relation in a Squeel::Relation class, and make an attempt to usurp all of the various calls to methods on ActiveRecord::Relation by doing some really evil stuff with constant reassignment, all for the sake of being able to use super().

  2. Submit a patch to Rails core, breaking these methods off into another module, all for my own selfish desire to use super() while mucking about in Rails internals.

  3. Use alias_method_chain, and say 10 hail Hanssons as penance.

I opted to go with #3. Except for the hail Hansson thing. Unless you’re DHH, in which case, I totally said them.

If you’d like to read more about alias_method_chain, see erniemiller.org/2011/02/03/when-to-use-alias_method_chain/



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 339

def self.included(base)
  base.class_eval do
    alias_method_chain :where_values_hash, :squeel
  end
end

Instance Method Details

#attribute_visitor ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 29

def attribute_visitor
  Visitors::AttributeVisitor.new(
    Context.new(join_dependency)
  )
end

#attrs_to_orderings(order) ⇒ Object

reverse_sql_order will reverse the order of strings or Orderings, but not attributes



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# File 'lib/squeel/adapters/active_record/3.1/relation_extensions.rb', line 100

def attrs_to_orderings(order)
  order.map do |o|
    Arel::Attribute === o ? o.asc : o
  end
end

#build_arel ⇒ Object 



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# File 'lib/squeel/adapters/active_record/relation_extensions.rb', line 8

def build_arel
  arel = table.from table

  build_join_dependency(arel, @joins_values) unless @joins_values.empty?

  predicate_viz = predicate_visitor
  attribute_viz = attribute_visitor

  collapse_wheres(arel, predicate_viz.accept((@where_values - ['']).uniq))

  arel.having(*predicate_viz.accept(@having_values.uniq.reject{|h| h.blank?})) unless @having_values.empty?

  arel.take(connection.sanitize_limit(@limit_value)) if @limit_value
  arel.skip(@offset_value) if @offset_value

  arel.group(*attribute_viz.accept(@group_values.uniq.reject{|g| g.blank?})) unless @group_values.empty?

  order = attribute_viz.accept(@order_values)
  order = reverse_sql_order(attrs_to_orderings(order)) if @reverse_order_value
  arel.order(*order.uniq.reject{|o| o.blank?}) unless order.empty?

  build_select(arel, attribute_viz.accept(@select_values.uniq))

  arel.distinct(@uniq_value)
  arel.from(@from_value) if @from_value
  arel.lock(@lock_value) if @lock_value

  arel
end

#build_join_dependency(manager, joins) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 124

def build_join_dependency(relation, joins)
  association_joins = []

  joins = joins.map {|j| j.respond_to?(:strip) ? j.strip : j}.uniq

  joins.each do |join|
    association_joins << join if [Hash, Array, Symbol, Nodes::Stub, Nodes::Join, Nodes::KeyPath].include?(join.class) && !array_of_strings?(join)
  end

  stashed_association_joins = joins.grep(::ActiveRecord::Associations::ClassMethods::JoinDependency::JoinAssociation)

  non_association_joins = (joins - association_joins - stashed_association_joins)
  custom_joins = custom_join_sql(*non_association_joins)

  self.join_dependency = JoinDependency.new(@klass, association_joins, custom_joins)

  join_dependency.graft(*stashed_association_joins)

  @implicit_readonly = true unless association_joins.empty? && stashed_association_joins.empty?

  to_join = []

  join_dependency.join_associations.each do |association|
    if (association_relation = association.relation).is_a?(Array)
      to_join << [association_relation.first, association.join_type, association.association_join.first]
      to_join << [association_relation.last, association.join_type, association.association_join.last]
    else
      to_join << [association_relation, association.join_type, association.association_join]
    end
  end

  to_join.uniq.each do |left, join_type, right|
    relation = relation.join(left, join_type).on(*right)
  end

  relation = relation.join(custom_joins)
end

#build_where(opts, other = []) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 248

def build_where(opts, other = [])
  case opts
  when String, Array
    super
  else  # Let's prevent PredicateBuilder from doing its thing
    [opts, *other].map do |arg|
      case arg
      when Array  # Just in case there's an array in there somewhere
        @klass.send(:sanitize_sql, arg)
      when Hash
        @klass.send(:expand_hash_conditions_for_aggregates, arg)
      else
        arg
      end
    end
  end
end

#collapse_wheres(arel, wheres) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 266

def collapse_wheres(arel, wheres)
  wheres = [wheres] unless Array === wheres
  binaries = wheres.grep(Arel::Nodes::Binary)

  groups = binaries.group_by {|b| [b.class, b.left]}

  groups.each do |_, bins|
    arel = arel.where(bins.inject(&:and))
  end

  (wheres - binaries).each do |where|
    where = Arel.sql(where) if String === where
    arel = arel.where(Arel::Nodes::Grouping.new(where))
  end

  arel
end

#debug_sql ⇒ Object

Simulate the logic that occurs in #to_a

This will let us get a dump of the SQL that will be run against the DB for debug purposes without actually running the query.



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 303

def debug_sql
  if eager_loading?
    including = (@eager_load_values + @includes_values).uniq
    join_dependency = JoinDependency.new(@klass, including, nil)
    construct_relation_for_association_find(join_dependency).to_sql
  else
    arel.to_sql
  end
end

#eager_load(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 178

def eager_load(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#find_equality_predicates(nodes) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 284

def find_equality_predicates(nodes)
  nodes.map { |node|
    case node
    when Arel::Nodes::Equality
      node if node.left.relation.name == table_name
    when Arel::Nodes::Grouping
      find_equality_predicates([node.expr])
    when Arel::Nodes::And
      find_equality_predicates(node.children)
    else
      nil
    end
  }.compact.flatten
end

#flatten_nodes(nodes) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.1/relation_extensions.rb', line 315

def flatten_nodes(nodes)
  nodes.map { |node|
    case node
    when Array
      flatten_nodes(node)
    when Nodes::And
      flatten_nodes(node.children)
    when Nodes::Grouping
      flatten_nodes(node.expr)
    else
      node
    end
  }.flatten
end

#group(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 200

def group(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#having(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 240

def having(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#includes(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 162

def includes(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#joins(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 224

def joins(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#merge(r, skip_visit = false) ⇒ Object

We need to be able to support merging two relations without having to get our hooks too deeply into ActiveRecord. AR’s relation merge functionality is very cool, but relatively complex, to handle the various edge cases. Our best shot at avoiding strange behavior with Squeel loaded is to visit the *_values arrays in the relations we’re merging, and then use the default AR merge code on the result.



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 42

def merge(r, skip_visit = false)
  if skip_visit or not ::ActiveRecord::Relation === r
    super(r)
  else
    visited.merge(r.visited, true)
  end
end

#order(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 208

def order(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#overwrite_squeel_equalities(wheres) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.1/relation_extensions.rb', line 330

def overwrite_squeel_equalities(wheres)
  seen = {}
  flatten_nodes(wheres).reverse.reject { |n|
    nuke = false
    if Nodes::Predicate === n && n.method_name == :eq
      nuke       = seen[n.expr]
      seen[n.expr] = true
    end
    nuke
  }.reverse
end

#predicate_visitor ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 23

def predicate_visitor
  Visitors::PredicateVisitor.new(
    Context.new(join_dependency)
  )
end

#preload(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 170

def preload(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#reorder(*args) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 216

def reorder(*args)
  if block_given? && args.empty?
    super(DSL.eval &Proc.new)
  else
    super
  end
end

#select(value = Proc.new) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 186

def select(value = Proc.new)
  if block_given? && Proc === value
    if value.arity > 0
      to_a.select {|*block_args| value.call(*block_args)}
    else
      relation = clone
      relation.select_values += Array.wrap(DSL.eval &value)
      relation
    end
  else
    super
  end
end

#select_for_count ⇒ Object

So, building a select for a count query in ActiveRecord is pretty heavily dependent on select_values containing strings. I’d initially expected that I could just hack together a fix to select_for_count and everything would fall in line, but unfortunately, pretty much everything from that point on in ActiveRecord::Calculations#perform_calculation expects the column to be a string, or at worst, a symbol.

In the long term, I would like to refactor the code in Rails core, but for now, I’m going to settle for this hack that tries really hard to coerce things to a string.



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 106

def select_for_count
  visited_values = attribute_visitor.accept(select_values.uniq)
  if visited_values.size == 1
    select = visited_values.first

    str_select = case select
    when String
      select
    when Symbol
      select.to_s
    else
      select.to_sql if select.respond_to?(:to_sql)
    end

    str_select if str_select && str_select !~ /[,*]/
  end
end

#visit! ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 54

def visit!
  predicate_viz = predicate_visitor
  attribute_viz = attribute_visitor

  @where_values = predicate_viz.accept((@where_values - ['']).uniq)
  @having_values = predicate_viz.accept(@having_values.uniq.reject{|h| h.blank?})
  # FIXME: AR barfs on ARel attributes in group_values. Workaround?
  # @group_values = attribute_viz.accept(@group_values.uniq.reject{|g| g.blank?})
  @order_values = attribute_viz.accept(@order_values.uniq.reject{|o| o.blank?})
  @select_values = attribute_viz.accept(@select_values.uniq)

  self
end

#visited ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 50

def visited
  clone.visit!
end

#where(opts = Proc.new, *rest) ⇒ Object 



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# File 'lib/squeel/adapters/active_record/3.0/relation_extensions.rb', line 232

def where(opts = Proc.new, *rest)
  if block_given? && Proc === opts
    super(DSL.eval &opts)
  else
    super
  end
end

#where_values_hash_with_squeel ⇒ Object

where_values_hash is used in scope_for_create. It’s what allows new records to be created with any equality values that exist in your model’s default scope. We hijack it in order to dig down into And and Grouping nodes, which are equivalent to seeing top-level Equality nodes in stock AR terms.



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# File 'lib/squeel/adapters/active_record/3.1/relation_extensions.rb', line 399

def where_values_hash_with_squeel
  equalities = find_equality_predicates(predicate_visitor.accept(@where_values))

  Hash[equalities.map { |where| [where.left.name, where.right] }]
end

#with_default_scope_with_squeel ⇒ Object

with_default_scope was added to ActiveRecord ~> 3.1 in order to address github.com/rails/rails/issues/1233. Unfortunately, it plays havoc with Squeel’s approach of visiting both sides of a relation merge. Thankfully, when merging with a relation from the same AR::Base, it’s unnecessary to visit…

Except, of course, this means we have to handle the edge case where equalities are duplicated on both sides of the merge, in which case, unlike all other chained relation calls, the latter equality overwrites the former.

The workaround using overwrite_squeel_equalities works as long as you stick to the Squeel DSL, but breaks down if you throw hash conditions into the mix. If anyone’s got any suggestions, I’m all ears. Otherwise, just stick to the Squeel DSL.

Or, don’t use default scopes. They’re the devil, anyway. I can’t remember the last time I used one and didn’t find myself regretting the decision later.



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# File 'lib/squeel/adapters/active_record/3.1/relation_extensions.rb', line 424

def with_default_scope_with_squeel
  if default_scoped? &&
    default_scope = klass.build_default_scope_with_squeel
    default_scope = default_scope.merge(self, true)
    default_scope.default_scoped = false
    default_scope.where_values = overwrite_squeel_equalities(
      default_scope.where_values + self.where_values
    )
    default_scope
  else
    self
  end
end