pg, PostgreSQL::Name to hold schema qualified names.

activerecord/lib/active_record/connection_adapters/postgresql/quoting.rb

@@ -150,12 +150,7 @@ module ActiveRecord
         # - "schema.name".table_name
         # - "schema.name"."table.name"
         def quote_table_name(name)
-          schema, table = Utils.extract_schema_and_table(name.to_s)
-          if schema
-            "#{quote_column_name(schema)}.#{quote_column_name(table)}"
-          else
-            quote_column_name(table)
-          end
+          Utils.extract_schema_qualified_name(name.to_s).quoted
         end
 
         def quote_table_name_for_assignment(table, attr)

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -97,16 +97,16 @@ module ActiveRecord
         # If the schema is not specified as part of +name+ then it will only find tables within
         # the current schema search path (regardless of permissions to access tables in other schemas)
         def table_exists?(name)
-          schema, table = Utils.extract_schema_and_table(name.to_s)
-          return false unless table
+          name = Utils.extract_schema_qualified_name(name.to_s)
+          return false unless name.identifier
 
           exec_query(<<-SQL, 'SCHEMA').rows.first[0].to_i > 0
               SELECT COUNT(*)
               FROM pg_class c
               LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
               WHERE c.relkind IN ('r','v','m') -- (r)elation/table, (v)iew, (m)aterialized view
-              AND c.relname = '#{table.gsub(/(^"|"$)/,'')}'
-              AND n.nspname = #{schema ? "'#{schema}'" : 'ANY (current_schemas(false))'}
+              AND c.relname = '#{name.identifier}'
+              AND n.nspname = #{name.schema ? "'#{name.schema}'" : 'ANY (current_schemas(false))'}
           SQL
         end
 

activerecord/lib/active_record/connection_adapters/postgresql/utils.rb

@@ -1,13 +1,54 @@
 module ActiveRecord
   module ConnectionAdapters
     module PostgreSQL
+      # Value Object to hold a schema qualified name.
+      # This is usually the name of a PostgreSQL relation but it can also represent
+      # schema qualified type names. +schema+ and +identifier+ are unquoted to prevent
+      # double quoting.
+      class Name # :nodoc:
+        SEPARATOR = "."
+        attr_reader :schema, :identifier
+
+        def initialize(schema, identifier)
+          @schema, @identifier = unquote(schema), unquote(identifier)
+        end
+
+        def to_s
+          parts.join SEPARATOR
+        end
+
+        def quoted
+          parts.map { |p| PGconn.quote_ident(p) }.join SEPARATOR
+        end
+
+        def ==(o)
+          o.class == self.class && o.parts == parts
+        end
+        alias_method :eql?, :==
+
+        def hash
+          parts.hash
+        end
+
+        protected
+          def unquote(part)
+            return unless part
+            part.gsub(/(^"|"$)/,'')
+          end
+
+          def parts
+            @parts ||= [@schema, @identifier].compact
+          end
+      end
+
       module Utils # :nodoc:
         extend self
 
-        # Returns an array of <tt>[schema_name, table_name]</tt> extracted from +name+.
-        # +schema_name+ is nil if not specified in +name+.
-        # +schema_name+ and +table_name+ exclude surrounding quotes (regardless of whether provided in +name+)
-        # +name+ supports the range of schema/table references understood by PostgreSQL, for example:
+        # Returns an instance of <tt>ActiveRecord::ConnectionAdapters::PostgreSQL::Name</tt>
+        # extracted from +string+.
+        # +schema+ is nil if not specified in +string+.
+        # +schema+ and +identifier+ exclude surrounding quotes (regardless of whether provided in +string+)
+        # +string+ supports the range of schema/table references understood by PostgreSQL, for example:
         #
         # * <tt>table_name</tt>
         # * <tt>"table.name"</tt>
@@ -15,9 +56,9 @@ module ActiveRecord
         # * <tt>schema_name."table.name"</tt>
         # * <tt>"schema_name".table_name</tt>
         # * <tt>"schema.name"."table name"</tt>
-        def extract_schema_and_table(name)
-          table, schema = name.scan(/[^".\s]+|"[^"]*"/)[0..1].collect{|m| m.gsub(/(^"|"$)/,'') }.reverse
-          [schema, table]
+        def extract_schema_qualified_name(string)
+          table, schema = string.scan(/[^".\s]+|"[^"]*"/)[0..1].reverse
+          PostgreSQL::Name.new(schema, table)
         end
       end
     end

activerecord/test/cases/adapters/postgresql/utils_test.rb

@@ -1,9 +1,10 @@
 require 'cases/helper'
 
 class PostgreSQLUtilsTest < ActiveSupport::TestCase
+  Name = ActiveRecord::ConnectionAdapters::PostgreSQL::Name
   include ActiveRecord::ConnectionAdapters::PostgreSQL::Utils
 
-  def test_extract_schema_and_table
+  def test_extract_schema_qualified_name
     {
       %(table_name)            => [nil,'table_name'],
       %("table.name")          => [nil,'table.name'],
@@ -14,7 +15,47 @@ class PostgreSQLUtilsTest < ActiveSupport::TestCase
       %("even spaces".table)   => ['even spaces','table'],
       %(schema."table.name")   => ['schema', 'table.name']
     }.each do |given, expect|
-      assert_equal expect, extract_schema_and_table(given)
+      assert_equal Name.new(*expect), extract_schema_qualified_name(given)
     end
   end
 end
+
+class PostgreSQLNameTest < ActiveSupport::TestCase
+  Name = ActiveRecord::ConnectionAdapters::PostgreSQL::Name
+
+  test "represents itself as schema.name" do
+    obj = Name.new("public", "articles")
+    assert_equal "public.articles", obj.to_s
+  end
+
+  test "without schema, represents itself as name only" do
+    obj = Name.new(nil, "articles")
+    assert_equal "articles", obj.to_s
+  end
+
+  test "quoted returns a string representation usable in a query" do
+    assert_equal %("articles"), Name.new(nil, "articles").quoted
+    assert_equal %("public"."articles"), Name.new("public", "articles").quoted
+  end
+
+  test "prevents double quoting" do
+    name = Name.new('"quoted_schema"', '"quoted_table"')
+    assert_equal "quoted_schema.quoted_table", name.to_s
+    assert_equal %("quoted_schema"."quoted_table"), name.quoted
+  end
+
+  test "equality based on state" do
+    assert_equal Name.new("access", "users"), Name.new("access", "users")
+    assert_equal Name.new(nil, "users"), Name.new(nil, "users")
+    assert_not_equal Name.new(nil, "users"), Name.new("access", "users")
+    assert_not_equal Name.new("access", "users"), Name.new("public", "users")
+    assert_not_equal Name.new("public", "users"), Name.new("public", "articles")
+  end
+
+  test "can be used as hash key" do
+    hash = {Name.new("schema", "article_seq") => "success"}
+    assert_equal "success", hash[Name.new("schema", "article_seq")]
+    assert_equal nil, hash[Name.new("schema", "articles")]
+    assert_equal nil, hash[Name.new("public", "article_seq")]
+  end
+end