support LOB equality

Author: akostadinov

lib/arel/visitors/oracle_common.rb

@@ -4,6 +4,21 @@ module Arel # :nodoc: all
   module Visitors
     module OracleCommon
       private
+        # Oracle can't compare CLOB columns with standard SQL operators for comparison.
+        # We need to replace standard equality for text/binary columns to use DBMS_LOB.COMPARE function.
+        # Fixes ORA-00932: inconsistent datatypes: expected - got CLOB
+        def visit_Arel_Nodes_Equality(o, collector)
+          left = o.left
+          return super unless Arel::Attributes::Attribute === left && %i(text binary).include?(column_for(left).type)
+
+          # https://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_lob.htm#i1016668
+          # returns 0 when the comparison succeeds
+          comparator = Arel::Nodes::NamedFunction.new("DBMS_LOB.COMPARE", [left, o.right])
+          collector = visit comparator, collector
+          collector << " = 0"
+          collector
+        end
+
         def visit_Arel_Nodes_Matches(o, collector)
           if !o.case_sensitive && o.left && o.right
             o.left = Arel::Nodes::NamedFunction.new("UPPER", [o.left])
@@ -12,6 +27,28 @@ def visit_Arel_Nodes_Matches(o, collector)
 
           super o, collector
         end
+
+        def column_for(attr)
+          return unless attr
+          name = attr.name.to_s
+          table = attr.relation.table_name
+
+          return nil unless table_exists? table
+
+          column_cache(table)[name]
+        end
+
+        def column_cache(table)
+          schema_cache.columns_hash(table)
+        end
+
+        def schema_cache
+          @connection.schema_cache
+        end
+
+        def table_exists?(name)
+          schema_cache.data_source_exists?(name)
+        end
     end
   end
 end

spec/active_record/oracle_enhanced/type/raw_spec.rb

@@ -119,4 +119,18 @@ class ::TestEmployee < ActiveRecord::Base
     @employee.reload
     expect(@employee.binary_data).to eq(@binary_data)
   end
+
+  it "should allow equality on select" do
+    TestEmployee.create!(
+      first_name: "First",
+      last_name: "Last",
+      binary_data: @binary_data,
+    )
+    TestEmployee.create!(
+      first_name: "First1",
+      last_name: "Last1",
+      binary_data: @binary_data2,
+    )
+    expect(TestEmployee.where(binary_data: @binary_data)).to have_attributes(count: 1)
+  end
 end

spec/active_record/oracle_enhanced/type/text_spec.rb

@@ -226,4 +226,19 @@ class ::TestSerializeEmployee < ActiveRecord::Base
     @employee.reload
     expect(@employee.comments).to eq(length: { is: 2 })
   end
+
+  it "should allow equality on select" do
+    search_data = "text search CLOB"
+    Test2Employee.create!(
+      first_name: "First",
+      last_name: "Last",
+      comments: search_data,
+    )
+    Test2Employee.create!(
+      first_name: "First1",
+      last_name: "Last1",
+      comments: "other data",
+    )
+    expect(Test2Employee.where(comments: search_data)).to have_attributes(count: 1)
+  end
 end