Class: Qdsl::Select

Inherits:
Object
  • Object
show all
Defined in:
lib/select.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(columns, &block) ⇒ Select

Returns a new instance of Select.



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# File 'lib/select.rb', line 19

def initialize(columns, &block)
  @columns = columns
  @block = block
  @inner_joins = []
end

Instance Attribute Details

#source ⇒ Object (readonly)

Returns the value of attribute source.



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# File 'lib/select.rb', line 17

def source
  @source
end

Instance Method Details

#add_inner_join(source, predicate) ⇒ Object 



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# File 'lib/select.rb', line 47

def add_inner_join(source, predicate)
  @inner_joins << InnerJoin.new(source, predicate)
  self
end

#create_query ⇒ Object 



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# File 'lib/select.rb', line 30

def create_query
  # Clone columns?
  column_names = @columns.collect(&:name)
  SelectQuery.new(self, column_names)
end

#from(source) ⇒ Object 



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# File 'lib/select.rb', line 25

def from(source)
  @source = source.create_query
  self
end

#inner_join(source) ⇒ Object 



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# File 'lib/select.rb', line 43

def inner_join(source)
  InnerJoinBuilder.new(self, source.create_query)
end

#render(context = nil, depth = 0) ⇒ Object 



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# File 'lib/select.rb', line 52

def render(context = nil, depth = 0)
  context ||= Context.new

  indent = '  ' * depth

  unknown_columns = @columns.select { |x| !@source.column_names.include?(x.name) }
  raise "One or more unknown columns: #{unknown_columns.collect(&:name).join(', ')}" unless unknown_columns.empty?

  columns = @columns.collect { |x| x.with_source(@source) }

  sources = [@source] + @inner_joins.collect(&:source)

  extra_columns = if @block
    proxies = sources.collect { |x| FunkyProxy.new(x) }
    [*@block.call(proxies.size == 1 ? proxies.first : proxies)]
  else
    []
  end

  ids = sources.inject({}) { |acc, x| acc[x] = context.id; acc }

  column_results = (columns + extra_columns).collect { |x| x.render(context, ids[x.source]) }

  fragments = []

  fragments << "#{indent}SELECT #{column_results.join(', ')}\n"
  fragments << "#{indent}FROM #{@source.render(context, depth + 1, ids[@source])}\n"

  @inner_joins.each do |inner_join|
    predicate_result = inner_join.predicate.render(context, ids)
    fragments << "#{indent}INNER JOIN #{inner_join.source.render(context, depth + 1, ids[inner_join.source])}\n"
    fragments << "#{indent}ON #{predicate_result}\n"
  end

  if @where
    predicate_result = @where.render(context, ids)
    fragments << "#{indent}WHERE #{predicate_result}"
  end

  fragments.join
end

#where ⇒ Object 



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# File 'lib/select.rb', line 36

def where
  sources = [@source] + @inner_joins.collect(&:source)
  proxies = sources.collect { |x| FunkyProxy.new(x) }
  @where = yield(proxies.size == 1 ? proxies.first : proxies)
  self
end