Rails PG adapter: Properly quote Infinity and NaN

refs CNVS-1368

This backports a Rails 3.1 fix as a monkey patch to our Rails 2.3.X
installation. It should address unquoted instances of Infinity we are
seeing occasionally in web conference queries.

The test plan for this is not UI-based, since I was unable to reproduce
by poking around the BigBlueButton web conferences UI.

Test Plan:
 - Inside a ./script/console, choose a model with a column of type
   "float", like WebConference
 - Try to create it with 0.0/0 and 1.0/0 as the value of that column,
   like BigBlueButtonConference.new(:duration => 0.0/0).save(false)
 - Verify that no database exceptions are thrown

The official Rails commit with this fix is here:

06c23c4c7f

Change-Id: I41141054aa06c88ed121a33e6e2da578ff9be82d
Reviewed-on: https://gerrit.instructure.com/17317
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Clare Hetherington <clare@instructure.com>

config/initializers/rails_patches.rb

@@ -203,4 +203,43 @@ else
       end
     end
   end
+
+  # Handle quoting properly for Infinity and NaN. This fix exists in Rails 3.1
+  # and can be safely removed once we upgrade.
+  #
+  # Adapted from: https://github.com/rails/rails/commit/06c23c4c7ff842f7c6237f3ac43fc9d19509a947
+  #
+  # This patch is covered by tests in spec/initializers/active_record_quoting_spec.rb
+  if defined?(ActiveRecord::ConnectionAdapters::PostgreSQLAdapter)
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.class_eval do
+      # Quotes PostgreSQL-specific data types for SQL input.
+      def quote(value, column = nil) #:nodoc:
+        if value.kind_of?(String) && column && column.type == :binary
+          "'#{escape_bytea(value)}'"
+        elsif value.kind_of?(String) && column && column.sql_type == 'xml'
+          "xml '#{quote_string(value)}'"
+        elsif value.kind_of?(Float)
+          if value.infinite? && column && column.type == :datetime
+            "'#{value.to_s.downcase}'"
+          elsif value.infinite? || value.nan?
+            "'#{value.to_s}'"
+          else
+            super
+          end
+        elsif value.kind_of?(Numeric) && column && column.sql_type == 'money'
+          # Not truly string input, so doesn't require (or allow) escape string syntax.
+          "'#{value.to_s}'"
+        elsif value.kind_of?(String) && column && column.sql_type =~ /^bit/
+          case value
+            when /^[01]*$/
+              "B'#{value}'" # Bit-string notation
+            when /^[0-9A-F]*$/i
+              "X'#{value}'" # Hexadecimal notation
+          end
+        else
+          super
+        end
+      end
+    end
+  end
 end

spec/initializers/active_record_quoting_spec.rb

@@ -0,0 +1,27 @@
+require File.expand_path('../spec_helper', File.dirname( __FILE__ ))
+
+module ActiveRecord
+  module ConnectionAdapters
+    describe PostgreSQLAdapter do
+      describe 'quoting' do
+        # These tests are adapted from the ActiveRecord tests located here:
+        # https://github.com/rails/rails/blob/06c23c4c7ff842f7c6237f3ac43fc9d19509a947/activerecord/test/cases/adapters/postgresql/quoting_test.rb
+        before do 
+          @conn = ActiveRecord::Base.connection
+        end
+
+        it 'properly quotes NaN' do
+          nan = 0.0/0
+          c = Column.new(nil, 1, 'float')
+          assert_equal "'NaN'", @conn.quote(nan, c)
+        end
+
+        it 'properly quotes Infinity' do
+          infinity = 1.0/0
+          c = Column.new(nil, 1, 'float')
+          assert_equal "'Infinity'", @conn.quote(infinity, c)
+        end
+      end
+    end
+  end
+end