Make class MyModel < Sequel::Model(DB[:table]) reload safe

The reason this didn't work before is because Dataset did not
implement an appropriate hash or == method.  This commit does
that.  Both == and hash check the database, options, and SQL
for the dataset.  I was originally planning on having them
check the row_proc, but that wouldn't work correctly with the
existing implementation of Sequel::Model().

CHANGELOG

@@ -1,5 +1,9 @@
 === HEAD
 
+* Make class MyModel < Sequel::Model(DB[:table]) reload safe (jeremyevans)
+
+* Fix a possible error when using the do (DataObjects) adapter with postgres (jeremyevans)
+
 * Handle a many_to_many :join_table option that uses an implicit alias (mluu, jeremyevans)
 
 * Work around bug in Microsoft's SQL Server JDBC Adapter version 3.0 (jfirebaugh)

lib/sequel/dataset/misc.rb

@@ -34,6 +34,17 @@ def initialize(db, opts = nil)
       @row_proc = nil
     end
 
+    # Define a hash value such that datasets with the same DB, opts, and SQL
+    # will be consider equal.
+    def ==(o)
+      o.is_a?(self.class) && db == o.db  && opts == o.opts && sql == o.sql
+    end
+
+    # Alias for ==
+    def eql?(o)
+      self == o
+    end
+
     # Return the dataset as an aliased expression with the given alias. You can
     # use this as a FROM or JOIN dataset, or as a column if this dataset
     # returns a single row and column.
@@ -105,6 +116,12 @@ def first_source_table
         s
       end
     end
+
+    # Define a hash value such that datasets with the same DB, opts, and SQL
+    # will have the same hash value
+    def hash
+      [db, opts.sort_by{|k| k.to_s}, sql].hash
+    end
 
     # Returns a string representation of the dataset including the class name 
     # and the corresponding SQL select statement.

spec/core/dataset_spec.rb

@@ -113,7 +113,7 @@
     @dataset.row_proc = Proc.new{|r| r}
     @clone = @dataset.clone
 
-    @clone.should_not === @dataset
+    @clone.object_id.should_not === @dataset.object_id
     @clone.class.should == @dataset.class
     @clone.opts.should == @dataset.opts
     @clone.row_proc.should == @dataset.row_proc
@@ -159,6 +159,58 @@ def __xyz__; "xyz"; end
   end
 end
 
+context "Dataset#==" do
+  before do
+    @db = MockDatabase.new
+    @h = {}
+  end
+
+  specify "should be the true for dataset with the same db, opts, and SQL" do
+    @db[:t].should == @db[:t]
+  end
+
+  specify "should be different for datasets with different dbs" do
+    @db[:t].should_not == MockDatabase.new[:t]
+  end
+
+  specify "should be different for datasets with different opts" do
+    @db[:t].should_not == @db[:t].clone(:blah=>1)
+  end
+
+  specify "should be different for datasets with different SQL" do
+    ds = @db[:t]
+    ds.quote_identifiers = true
+    ds.should_not == @db[:t]
+  end
+end
+
+context "Dataset#hash" do
+  before do
+    @db = MockDatabase.new
+    @h = {}
+  end
+
+  specify "should be the same for dataset with the same db, opts, and SQL" do
+    @db[:t].hash.should == @db[:t].hash
+    @h[@db[:t]] = 1
+    @h[@db[:t]].should == 1
+  end
+
+  specify "should be different for datasets with different dbs" do
+    @db[:t].hash.should_not == MockDatabase.new[:t].hash
+  end
+
+  specify "should be different for datasets with different opts" do
+    @db[:t].hash.should_not == @db[:t].clone(:blah=>1).hash
+  end
+
+  specify "should be different for datasets with different SQL" do
+    ds = @db[:t]
+    ds.quote_identifiers = true
+    ds.hash.should_not == @db[:t].hash
+  end
+end
+
 context "A simple dataset" do
   before do
     @dataset = Sequel::Dataset.new(nil).from(:test)

spec/model/base_spec.rb

@@ -408,18 +408,18 @@ def refresh
   end
 
   it "should depend on whether the dataset provides an accurate number of rows matched by default" do
-    Class.new(Sequel::Model(@ds1)).require_modification.should == false
-    Class.new(Sequel::Model(@ds2)).require_modification.should == true
+    Class.new(Sequel::Model).set_dataset(@ds1).require_modification.should == false
+    Class.new(Sequel::Model).set_dataset(@ds2).require_modification.should == true
   end
 
   it "should obey global setting regardless of dataset support if set" do
     Sequel::Model.require_modification = true
-    Class.new(Sequel::Model(@ds1)).require_modification.should == true
-    Class.new(Sequel::Model(@ds2)).require_modification.should == true
+    Class.new(Sequel::Model).set_dataset(@ds1).require_modification.should == true
+    Class.new(Sequel::Model).set_dataset(@ds2).require_modification.should == true
 
     Sequel::Model.require_modification = false
-    Class.new(Sequel::Model(@ds1)).require_modification.should == false
-    Class.new(Sequel::Model(@ds2)).require_modification.should == false
+    Class.new(Sequel::Model).set_dataset(@ds1).require_modification.should == false
+    Class.new(Sequel::Model).set_dataset(@ds1).require_modification.should == false
   end
 end
 

spec/model/model_spec.rb

@@ -30,6 +30,33 @@ class SmBlahTest < c
     SmBlahTest.db.should == db
     SmBlahTest.table_name.should == :sm_blah_tests
   end
+
+  describe "reloading" do
+    after do
+      Object.send(:remove_const, :Album) if defined?(::Album)
+    end
+
+    it "should work without raising an exception with a symbol" do
+      proc do
+        class ::Album < Sequel::Model(:table); end
+        class ::Album < Sequel::Model(:table); end
+      end.should_not raise_error
+    end
+
+    it "should work without raising an exception with a database" do
+      proc do
+        class ::Album < Sequel::Model(@db); end
+        class ::Album < Sequel::Model(@db); end
+      end.should_not raise_error
+    end
+
+    it "should work without raising an exception with a dataset" do
+      proc do
+        class ::Album < Sequel::Model(@db[:table]); end
+        class ::Album < Sequel::Model(@db[:table]); end
+      end.should_not raise_error
+    end
+  end
 end
 
 describe Sequel::Model do