1 files changed, 272 insertions, 0 deletions
diff --git a/activerecord/lib/arel/select_manager.rb b/activerecord/lib/arel/select_manager.rb
new file mode 100644
index 0000000000..0f3b0dc6a0
--- /dev/null
+++ b/activerecord/lib/arel/select_manager.rb
@@ -0,0 +1,272 @@
+# frozen_string_literal: true
+module Arel
+  class SelectManager < Arel::TreeManager
+    include Arel::Crud
+
+    STRING_OR_SYMBOL_CLASS = [Symbol, String]
+
+    def initialize table = nil
+      super()
+      @ast   = Nodes::SelectStatement.new
+      @ctx    = @ast.cores.last
+      from table
+    end
+
+    def initialize_copy other
+      super
+      @ctx = @ast.cores.last
+    end
+
+    def limit
+      @ast.limit && @ast.limit.expr
+    end
+    alias :taken :limit
+
+    def constraints
+      @ctx.wheres
+    end
+
+    def offset
+      @ast.offset && @ast.offset.expr
+    end
+
+    def skip amount
+      if amount
+        @ast.offset = Nodes::Offset.new(amount)
+      else
+        @ast.offset = nil
+      end
+      self
+    end
+    alias :offset= :skip
+
+    ###
+    # Produces an Arel::Nodes::Exists node
+    def exists
+      Arel::Nodes::Exists.new @ast
+    end
+
+    def as other
+      create_table_alias grouping(@ast), Nodes::SqlLiteral.new(other)
+    end
+
+    def lock locking = Arel.sql('FOR UPDATE')
+      case locking
+      when true
+        locking = Arel.sql('FOR UPDATE')
+      when Arel::Nodes::SqlLiteral
+      when String
+        locking = Arel.sql locking
+      end
+
+      @ast.lock = Nodes::Lock.new(locking)
+      self
+    end
+
+    def locked
+      @ast.lock
+    end
+
+    def on *exprs
+      @ctx.source.right.last.right = Nodes::On.new(collapse(exprs))
+      self
+    end
+
+    def group *columns
+      columns.each do |column|
+        # FIXME: backwards compat
+        column = Nodes::SqlLiteral.new(column) if String === column
+        column = Nodes::SqlLiteral.new(column.to_s) if Symbol === column
+
+        @ctx.groups.push Nodes::Group.new column
+      end
+      self
+    end
+
+    def from table
+      table = Nodes::SqlLiteral.new(table) if String === table
+
+      case table
+      when Nodes::Join
+        @ctx.source.right << table
+      else
+        @ctx.source.left = table
+      end
+
+      self
+    end
+
+    def froms
+      @ast.cores.map { |x| x.from }.compact
+    end
+
+    def join relation, klass = Nodes::InnerJoin
+      return self unless relation
+
+      case relation
+      when String, Nodes::SqlLiteral
+        raise EmptyJoinError if relation.empty?
+        klass = Nodes::StringJoin
+      end
+
+      @ctx.source.right << create_join(relation, nil, klass)
+      self
+    end
+
+    def outer_join relation
+      join(relation, Nodes::OuterJoin)
+    end
+
+    def having expr
+      @ctx.havings << expr
+      self
+    end
+
+    def window name
+      window = Nodes::NamedWindow.new(name)
+      @ctx.windows.push window
+      window
+    end
+
+    def project *projections
+      # FIXME: converting these to SQLLiterals is probably not good, but
+      # rails tests require it.
+      @ctx.projections.concat projections.map { |x|
+        STRING_OR_SYMBOL_CLASS.include?(x.class) ? Nodes::SqlLiteral.new(x.to_s) : x
+      }
+      self
+    end
+
+    def projections
+      @ctx.projections
+    end
+
+    def projections= projections
+      @ctx.projections = projections
+    end
+
+    def distinct(value = true)
+      if value
+        @ctx.set_quantifier = Arel::Nodes::Distinct.new
+      else
+        @ctx.set_quantifier = nil
+      end
+      self
+    end
+
+    def distinct_on(value)
+      if value
+        @ctx.set_quantifier = Arel::Nodes::DistinctOn.new(value)
+      else
+        @ctx.set_quantifier = nil
+      end
+      self
+    end
+
+    def order *expr
+      # FIXME: We SHOULD NOT be converting these to SqlLiteral automatically
+      @ast.orders.concat expr.map { |x|
+        STRING_OR_SYMBOL_CLASS.include?(x.class) ? Nodes::SqlLiteral.new(x.to_s) : x
+      }
+      self
+    end
+
+    def orders
+      @ast.orders
+    end
+
+    def where_sql engine = Table.engine
+      return if @ctx.wheres.empty?
+
+      viz = Visitors::WhereSql.new(engine.connection.visitor, engine.connection)
+      Nodes::SqlLiteral.new viz.accept(@ctx, Collectors::SQLString.new).value
+    end
+
+    def union operation, other = nil
+      if other
+        node_class = Nodes.const_get("Union#{operation.to_s.capitalize}")
+      else
+        other = operation
+        node_class = Nodes::Union
+      end
+
+      node_class.new self.ast, other.ast
+    end
+
+    def intersect other
+      Nodes::Intersect.new ast, other.ast
+    end
+
+    def except other
+      Nodes::Except.new ast, other.ast
+    end
+    alias :minus :except
+
+    def lateral table_name = nil
+      base = table_name.nil? ? ast : as(table_name)
+      Nodes::Lateral.new(base)
+    end
+
+    def with *subqueries
+      if subqueries.first.is_a? Symbol
+        node_class = Nodes.const_get("With#{subqueries.shift.to_s.capitalize}")
+      else
+        node_class = Nodes::With
+      end
+      @ast.with = node_class.new(subqueries.flatten)
+
+      self
+    end
+
+    def take limit
+      if limit
+        @ast.limit = Nodes::Limit.new(limit)
+        @ctx.top   = Nodes::Top.new(limit)
+      else
+        @ast.limit = nil
+        @ctx.top   = nil
+      end
+      self
+    end
+    alias limit= take
+
+    def join_sources
+      @ctx.source.right
+    end
+
+    def source
+      @ctx.source
+    end
+
+    class Row < Struct.new(:data) # :nodoc:
+      def id
+        data['id']
+      end
+
+      def method_missing(name, *args)
+        name = name.to_s
+        return data[name] if data.key?(name)
+        super
+      end
+    end
+
+    private
+    def collapse exprs, existing = nil
+      exprs = exprs.unshift(existing.expr) if existing
+      exprs = exprs.compact.map { |expr|
+        if String === expr
+          # FIXME: Don't do this automatically
+          Arel.sql(expr)
+        else
+          expr
+        end
+      }
+
+      if exprs.length == 1
+        exprs.first
+      else
+        create_and exprs
+      end
+    end
+  end
+end