initial import

Rakefile

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+require 'rubygems'
+require 'spec'
+require 'spec/rake/spectask'
+
+Spec::Rake::SpecTask.new do |t|
+  t.spec_files = FileList['spec/**/*_spec.rb']
+end
+
+desc "Default task is to run specs"
+task :default => :spec

lib/sql_algebra.rb

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+$LOAD_PATH.unshift(File.dirname(__FILE__))
+require 'rubygems'
+require 'active_support'
+
+require 'sql_algebra/relations/relation'
+require 'sql_algebra/relations/table_relation'
+require 'sql_algebra/relations/join_operation'
+require 'sql_algebra/relations/join_relation'
+require 'sql_algebra/relations/attribute'
+
+require 'sql_algebra/relations/predicates/predicate'
+require 'sql_algebra/relations/predicates/binary_predicate'
+require 'sql_algebra/relations/predicates/equality_predicate'
+require 'sql_algebra/relations/predicates/less_than_predicate'
+require 'sql_algebra/relations/predicates/less_than_or_equal_to_predicate'
+require 'sql_algebra/relations/predicates/greater_than_predicate'
+require 'sql_algebra/relations/predicates/greater_than_or_equal_to_predicate'
+require 'sql_algebra/relations/predicates/range_inclusion_predicate'
+require 'sql_algebra/relations/predicates/relation_inclusion_predicate'
+require 'sql_algebra/relations/predicates/match_predicate'
+
+require 'sql_algebra/extensions/range'
+
+require 'sql_algebra/sql/select'

lib/sql_algebra/relations/attribute.rb

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+class Attribute
+  attr_reader :relation, :attribute_name
+
+  def initialize(relation, attribute_name)
+    @relation, @attribute_name = relation, attribute_name
+  end
+
+  def eql?(other)
+    relation == other.relation and attribute_name == other.attribute_name
+  end
+
+  def ==(other)
+    EqualityPredicate.new(self, other)
+  end
+
+  def <(other)
+    LessThanPredicate.new(self, other)
+  end
+
+  def <=(other)
+    LessThanOrEqualToPredicate.new(self, other)
+  end
+
+  def >(other)
+    GreaterThanPredicate.new(self, other)
+  end
+
+  def >=(other)
+    GreaterThanOrEqualToPredicate.new(self, other)
+  end
+
+  def =~(regexp)
+    MatchPredicate.new(self, regexp)
+  end
+end

lib/sql_algebra/relations/join_operation.rb

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+class JoinOperation
+  attr_reader :relation1, :relation2
+
+  def initialize(relation1, relation2)
+    @relation1, @relation2 = relation1, relation2
+  end
+
+  def on(*predicates)
+    JoinRelation.new(relation1, relation2, *predicates)
+  end
+
+  def ==(other)
+    (relation1 == other.relation1 and relation2 == other.relation2) or
+      (relation1 == other.relation2 and relation2 == other.relation1)
+  end
+end

lib/sql_algebra/relations/join_relation.rb

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+class JoinRelation < Relation
+  attr_reader :relation1, :relation2, :predicates
+
+  def initialize(relation1, relation2, *predicates)
+    @relation1, @relation2, @predicates = relation1, relation2, predicates
+  end
+
+  def ==(other)
+    predicates == other.predicates and
+      ((relation1 == other.relation1 and relation2 == other.relation2) or
+      (relation2 == other.relation1 and relation1 == other.relation2))
+  end
+end

lib/sql_algebra/relations/predicates/binary_predicate.rb

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+class BinaryPredicate < Predicate
+  attr_reader :attribute1, :attribute2
+
+  def initialize(attribute1, attribute2)
+    @attribute1, @attribute2 = attribute1, attribute2
+  end
+
+  def ==(other)
+    super and
+      (attribute1.eql?(other.attribute1) and attribute2.eql?(other.attribute2))
+  end
+end

lib/sql_algebra/relations/predicates/equality_predicate.rb

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+class EqualityPredicate < BinaryPredicate
+  def ==(other)
+    self.class == other.class and
+      ((attribute1.eql?(other.attribute1) and attribute2.eql?(other.attribute2)) or
+       (attribute1.eql?(other.attribute2) and attribute2.eql?(other.attribute1)))
+  end
+end

lib/sql_algebra/relations/predicates/greater_than_or_equal_to_predicate.rb

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+class GreaterThanOrEqualToPredicate < BinaryPredicate
+end

lib/sql_algebra/relations/predicates/greater_than_predicate.rb

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+class GreaterThanPredicate < BinaryPredicate
+end

lib/sql_algebra/relations/predicates/less_than_or_equal_to_predicate.rb

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+class LessThanOrEqualToPredicate < BinaryPredicate
+end

lib/sql_algebra/relations/predicates/less_than_predicate.rb

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+class LessThanPredicate < BinaryPredicate
+end

lib/sql_algebra/relations/predicates/match_predicate.rb

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+class MatchPredicate < Predicate
+  attr_reader :attribute, :regexp
+
+  def initialize(attribute, regexp)
+    @attribute, @regexp = attribute, regexp
+  end
+end

lib/sql_algebra/relations/predicates/predicate.rb

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+class Predicate
+  def ==(other)
+    self.class == other.class
+  end
+end

lib/sql_algebra/relations/predicates/relation_inclusion_predicate.rb

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+class RelationInclusionPredicate < Predicate
+  attr_reader :attribute, :relation
+
+  def initialize(attribute, relation)
+    @attribute, @relation = attribute, relation
+  end
+
+  def ==(other)
+    super and attribute == other.attribute and relation == other.relation
+  end
+end

lib/sql_algebra/relations/relation.rb

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+class Relation
+  def *(other)
+    JoinOperation.new(self, other)
+  end
+
+  def [](attribute_name)
+    Attribute.new(self, attribute_name)
+  end
+
+  def include?(attribute)
+    RelationInclusionPredicate.new(attribute, self)
+  end
+end

lib/sql_algebra/relations/table_relation.rb

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+class TableRelation < Relation
+  attr_reader :table
+
+  def initialize(table)
+    @table = table
+  end
+
+  def to_sql
+    Select.new(:*).from(table)
+  end
+end

lib/sql_algebra/sql/select.rb

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+class Select
+  attr_reader :attributes, :tables, :predicates
+
+  def initialize(*attributes)
+    @attributes = attributes
+  end
+
+  def from(*tables)
+    returning self do |select|
+      @tables = tables
+    end
+  end
+
+  def where(*predicates)
+    returning self do |select|
+      @predicates = predicates
+    end
+  end
+
+  def ==(other)
+    attributes == other.attributes and tables == other.tables and predicates == other.predicates
+  end
+end

spec/extensions/range_spec.rb

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+require File.join(File.dirname(__FILE__), '..', 'spec_helper')

spec/predicates/binary_predicate_spec.rb

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+require File.join(File.dirname(__FILE__), '..', 'spec_helper')
+
+describe BinaryPredicate do
+  before do
+    @relation1 = TableRelation.new(:foo)
+    @relation2 = TableRelation.new(:bar)
+    @attribute1 = Attribute.new(@relation1, :attribute_name)
+    @attribute2 = Attribute.new(@relation2, :attribute_name)
+  end
+
+  describe BinaryPredicate, '==' do
+    before do
+      class ConcreteBinaryPredicate < BinaryPredicate
+      end
+    end
+
+    it "obtains if attribute1 and attribute2 are identical" do
+      BinaryPredicate.new(@attribute1, @attribute2).should == BinaryPredicate.new(@attribute1, @attribute2)
+      BinaryPredicate.new(@attribute1, @attribute2).should_not == BinaryPredicate.new(@attribute1, @attribute1)
+    end
+
+    it "obtains if the concrete type of the BinaryPredicates are identical" do
+      ConcreteBinaryPredicate.new(@attribute1, @attribute2).should == ConcreteBinaryPredicate.new(@attribute1, @attribute2)
+      BinaryPredicate.new(@attribute1, @attribute2).should_not == ConcreteBinaryPredicate.new(@attribute1, @attribute2)
+    end
+  end
+end

spec/predicates/equality_predicate_spec.rb

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+require File.join(File.dirname(__FILE__), '..', 'spec_helper')
+
+describe EqualityPredicate do
+  before do
+    @relation1 = TableRelation.new(:foo)
+    @relation2 = TableRelation.new(:bar)
+    @attribute1 = Attribute.new(@relation1, :attribute_name)
+    @attribute2 = Attribute.new(@relation2, :attribute_name)
+  end
+
+  describe EqualityPredicate, '==' do 
+    it "obtains if attribute1 and attribute2 are identical" do
+      EqualityPredicate.new(@attribute1, @attribute2).should == EqualityPredicate.new(@attribute1, @attribute2)
+      EqualityPredicate.new(@attribute1, @attribute2).should_not == EqualityPredicate.new(@attribute1, @attribute1)
+    end
+
+    it "obtains if the concrete type of the predicates are identical" do
+      EqualityPredicate.new(@attribute1, @attribute2).should_not == BinaryPredicate.new(@attribute1, @attribute2)
+    end
+
+    it "is commutative on the attributes" do
+      EqualityPredicate.new(@attribute1, @attribute2).should == EqualityPredicate.new(@attribute2, @attribute1)
+    end
+  end
+end

spec/predicates/relation_inclusion_predicate_spec.rb

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+require File.join(File.dirname(__FILE__), '..', 'spec_helper')
+
+describe RelationInclusionPredicate do
+  before do
+    @relation1 = TableRelation.new(:foo)
+    @relation2 = TableRelation.new(:bar)
+    @attribute = @relation1[:baz]
+  end
+
+  describe RelationInclusionPredicate, '==' do    
+    it "obtains if attribute1 and attribute2 are identical" do
+      RelationInclusionPredicate.new(@attribute, @relation1).should == RelationInclusionPredicate.new(@attribute, @relation1)
+      RelationInclusionPredicate.new(@attribute, @relation1).should_not == RelationInclusionPredicate.new(@attribute, @relation2)
+    end
+  end
+end

spec/relations/attribute_spec.rb

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+require File.join(File.dirname(__FILE__), '..', 'spec_helper')
+
+describe Attribute do
+  before do
+    @relation1 = TableRelation.new(:foo)
+    @relation2 = TableRelation.new(:bar)
+  end
+
+  describe Attribute, '#eql?' do
+    it "obtains if the relation and attribute name are identical" do
+      Attribute.new(@relation1, :attribute_name).should be_eql(Attribute.new(@relation1, :attribute_name))
+      Attribute.new(@relation1, :attribute_name).should_not be_eql(Attribute.new(@relation1, :another_attribute_name))
+      Attribute.new(@relation1, :attribute_name).should_not be_eql(Attribute.new(@relation2, :attribute_name))
+    end
+  end
+
+  describe Attribute, 'predications' do
+    before do
+      @attribute1 = Attribute.new(@relation1, :attribute_name)
+      @attribute2 = Attribute.new(@relation2, :attribute_name)
+    end
+
+    describe Attribute, '==' do
+      it "manufactures an equality predicate" do
+        (@attribute1 == @attribute2).should == EqualityPredicate.new(@attribute1, @attribute2)
+      end
+    end
+
+    describe Attribute, '<' do
+      it "manufactures a less-than predicate" do
+        (@attribute1 < @attribute2).should == LessThanPredicate.new(@attribute1, @attribute2)
+      end
+    end
+
+    describe Attribute, '<=' do
+      it "manufactures a less-than or equal-to predicate" do
+        (@attribute1 <= @attribute2).should == LessThanOrEqualToPredicate.new(@attribute1, @attribute2)
+      end
+    end
+
+    describe Attribute, '>' do
+      it "manufactures a greater-than predicate" do
+        (@attribute1 > @attribute2).should == GreaterThanPredicate.new(@attribute1, @attribute2)
+      end
+    end
+
+    describe Attribute, '>=' do
+      it "manufactures a greater-than or equal to predicate" do
+        (@attribute1 >= @attribute2).should == GreaterThanOrEqualToPredicate.new(@attribute1, @attribute2)
+      end
+    end
+
+    describe Attribute, '=~' do
+      it "manufactures a match predicate" do
+        (@attribute1 =~ /.*/).should == MatchPredicate.new(@attribute1, @attribute2)
+      end
+    end
+
+  end
+end

spec/relations/join_operation_spec.rb

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+require File.join(File.dirname(__FILE__), '..', 'spec_helper')
+
+describe JoinOperation, 'between two relations' do
+  before do
+    @relation1 = TableRelation.new(:foo)
+    @relation2 = TableRelation.new(:bar)
+  end
+
+  describe JoinOperation, '==' do
+    it "obtains if the relations of both joins are identical" do
+      JoinOperation.new(@relation1, @relation2).should == JoinOperation.new(@relation1, @relation2)
+      JoinOperation.new(@relation1, @relation2).should_not == JoinOperation.new(@relation1, @relation1)
+    end
+
+    it "is commutative on the relations" do
+      JoinOperation.new(@relation1, @relation2).should == JoinOperation.new(@relation2, @relation1)
+    end
+  end
+
+  describe JoinOperation, 'on' do
+    before do
+      @predicate = Predicate.new
+    end
+
+    it "manufactures a JoinRelation" do
+      JoinOperation.new(@relation1, @relation2).on(@predicate).should == JoinRelation.new(@relation1, @relation2, @predicate)
+    end
+  end
+end