Add Expression Indexes and Operator Classes support for PostgreSQL

Example:

    create_table :users do |t|
      t.string :name
      t.index 'lower(name) varchar_pattern_ops'
    end

Fixes #19090.
Fixes #21765.
Fixes #21819.
Fixes #24359.

Signed-off-by: Jeremy Daer <jeremydaer@gmail.com>

10 files changed, 112 insertions, 38 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 2de1fc9253..e76b0973ca 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,16 @@
+*   PostgreSQL: Support Expression Indexes and Operator Classes.
+
+    Example:
+
+        create_table :users do |t|
+          t.string :name
+          t.index 'lower(name) varchar_pattern_ops'
+        end
+
+    Fixes #19090, #21765, #21819, #24359.
+
+    *Ryuta Kamizono*
+
 *   MySQL: Prepared statements support.
 
     To enable, set `prepared_statements: true` in config/database.yml.
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index f65dc4ed5a..99a3e99bdc 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -1110,15 +1110,19 @@ module ActiveRecord
         Table.new(table_name, base)
       end
 
-      def add_index_options(table_name, column_name, comment: nil, **options) #:nodoc:
-        column_names = Array(column_name)
+      def add_index_options(table_name, column_name, comment: nil, **options) # :nodoc:
+        if column_name.is_a?(String) && /\W/ === column_name
+          column_names = column_name
+        else
+          column_names = Array(column_name)
+        end
 
         options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type)
 
         index_type = options[:type].to_s if options.key?(:type)
         index_type ||= options[:unique] ? "UNIQUE" : ""
         index_name = options[:name].to_s if options.key?(:name)
-        index_name ||= index_name(table_name, column: column_names)
+        index_name ||= index_name(table_name, index_name_options(column_names))
         max_index_length = options.fetch(:internal, false) ? index_name_length : allowed_index_name_length
 
         if options.key?(:algorithm)
@@ -1174,6 +1178,8 @@ module ActiveRecord
 
         # Overridden by the MySQL adapter for supporting index lengths
         def quoted_columns_for_index(column_names, options = {})
+          return [column_names] if column_names.is_a?(String)
+
           option_strings = Hash[column_names.map {|name| [name, '']}]
 
           # add index sort order if supported
@@ -1249,6 +1255,14 @@ module ActiveRecord
         AlterTable.new create_table_definition(name)
       end
 
+      def index_name_options(column_names) # :nodoc:
+        if column_names.is_a?(String)
+          column_names = column_names.scan(/\w+/).join('_')
+        end
+
+        { column: column_names }
+      end
+
       def foreign_key_name(table_name, options) # :nodoc:
         identifier = "#{table_name}_#{options.fetch(:column)}_fk"
         hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 130c03dd1d..86de8f1ca0 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -248,6 +248,11 @@ module ActiveRecord
         false
       end
 
+      # Does this adapter support expression indices?
+      def supports_expression_index?
+        false
+      end
+
       # Does this adapter support explain?
       def supports_explain?
         false
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index 272e6293ab..074ebb90a5 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -175,7 +175,10 @@ module ActiveRecord
 
           result = query(<<-SQL, 'SCHEMA')
             SELECT distinct i.relname, d.indisunique, d.indkey, pg_get_indexdef(d.indexrelid), t.oid,
-                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment
+                            pg_catalog.obj_description(i.oid, 'pg_class') AS comment,
+            (SELECT COUNT(*) FROM pg_opclass o
+               JOIN (SELECT unnest(string_to_array(d.indclass::text, ' '))::int oid) c
+                 ON o.oid = c.oid WHERE o.opcdefault = 'f')
             FROM pg_class t
             INNER JOIN pg_index d ON t.oid = d.indrelid
             INNER JOIN pg_class i ON d.indexrelid = i.oid
@@ -194,25 +197,27 @@ module ActiveRecord
             inddef = row[3]
             oid = row[4]
             comment = row[5]
+            opclass = row[6]
 
-            columns = Hash[query(<<-SQL, "SCHEMA")]
-            SELECT a.attnum, a.attname
-            FROM pg_attribute a
-            WHERE a.attrelid = #{oid}
-            AND a.attnum IN (#{indkey.join(",")})
-            SQL
+            using, expressions, where = inddef.scan(/ USING (\w+?) \((.+?)\)(?: WHERE (.+))?\z/).flatten
 
-            column_names = columns.values_at(*indkey).compact
+            if indkey.include?(0) || opclass > 0
+              columns = expressions
+            else
+              columns = Hash[query(<<-SQL.strip_heredoc, "SCHEMA")].values_at(*indkey).compact
+                SELECT a.attnum, a.attname
+                FROM pg_attribute a
+                WHERE a.attrelid = #{oid}
+                AND a.attnum IN (#{indkey.join(",")})
+              SQL
 
-            unless column_names.empty?
               # add info on sort order for columns (only desc order is explicitly specified, asc is the default)
-              desc_order_columns = inddef.scan(/(\w+) DESC/).flatten
-              orders = desc_order_columns.any? ? Hash[desc_order_columns.map {|order_column| [order_column, :desc]}] : {}
-              where = inddef.scan(/WHERE (.+)$/).flatten[0]
-              using = inddef.scan(/USING (.+?) /).flatten[0].to_sym
-
-              IndexDefinition.new(table_name, index_name, unique, column_names, [], orders, where, nil, using, comment)
+              orders = Hash[
+                expressions.scan(/(\w+) DESC/).flatten.map { |order_column| [order_column, :desc] }
+              ]
             end
+
+            IndexDefinition.new(table_name, index_name, unique, columns, [], orders, where, nil, using.to_sym, comment)
           end.compact
         end
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index e397a28cac..39a2cbbda7 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -140,6 +140,10 @@ module ActiveRecord
         true
       end
 
+      def supports_expression_index?
+        true
+      end
+
       def supports_transaction_isolation?
         true
       end
diff --git a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
index edb391b525..439e2ce6f7 100644
--- a/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/active_schema_test.rb
@@ -28,7 +28,13 @@ class PostgresqlActiveSchemaTest < ActiveRecord::PostgreSQLTestCase
     ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.send(:define_method, :index_name_exists?) { |*| false }
 
     expected = %(CREATE UNIQUE INDEX  "index_people_on_last_name" ON "people"  ("last_name") WHERE state = 'active')
-    assert_equal expected, add_index(:people, :last_name, :unique => true, :where => "state = 'active'")
+    assert_equal expected, add_index(:people, :last_name, unique: true, where: "state = 'active'")
+
+    expected = %(CREATE UNIQUE INDEX  "index_people_on_lower_last_name" ON "people"  (lower(last_name)))
+    assert_equal expected, add_index(:people, 'lower(last_name)', unique: true)
+
+    expected = %(CREATE UNIQUE INDEX  "index_people_on_last_name_varchar_pattern_ops" ON "people"  (last_name varchar_pattern_ops))
+    assert_equal expected, add_index(:people, 'last_name varchar_pattern_ops', unique: true)
 
     expected = %(CREATE  INDEX CONCURRENTLY "index_people_on_last_name" ON "people"  ("last_name"))
     assert_equal expected, add_index(:people, :last_name, algorithm: :concurrently)
@@ -39,16 +45,17 @@ class PostgresqlActiveSchemaTest < ActiveRecord::PostgreSQLTestCase
 
       expected = %(CREATE  INDEX CONCURRENTLY "index_people_on_last_name" ON "people" USING #{type} ("last_name"))
       assert_equal expected, add_index(:people, :last_name, using: type, algorithm: :concurrently)
+
+      expected = %(CREATE UNIQUE INDEX  "index_people_on_last_name" ON "people" USING #{type} ("last_name") WHERE state = 'active')
+      assert_equal expected, add_index(:people, :last_name, using: type, unique: true, where: "state = 'active'")
+
+      expected = %(CREATE UNIQUE INDEX  "index_people_on_lower_last_name" ON "people" USING #{type} (lower(last_name)))
+      assert_equal expected, add_index(:people, 'lower(last_name)', using: type, unique: true)
     end
 
     assert_raise ArgumentError do
       add_index(:people, :last_name, algorithm: :copy)
     end
-    expected = %(CREATE UNIQUE INDEX  "index_people_on_last_name" ON "people" USING gist ("last_name"))
-    assert_equal expected, add_index(:people, :last_name, :unique => true, :using => :gist)
-
-    expected = %(CREATE UNIQUE INDEX  "index_people_on_last_name" ON "people" USING gist ("last_name") WHERE state = 'active')
-    assert_equal expected, add_index(:people, :last_name, :unique => true, :where => "state = 'active'", :using => :gist)
 
     ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.send :remove_method, :index_name_exists?
   end
diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index 8b08ebc3c4..9832df7839 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -259,6 +259,22 @@ module ActiveRecord
         end
       end
 
+      def test_expression_index
+        with_example_table do
+          @connection.add_index 'ex', 'mod(id, 10), abs(number)', name: 'expression'
+          index = @connection.indexes('ex').find { |idx| idx.name == 'expression' }
+          assert_equal 'mod(id, 10), abs(number)', index.columns
+        end
+      end
+
+      def test_index_with_opclass
+        with_example_table do
+          @connection.add_index 'ex', 'data varchar_pattern_ops', name: 'with_opclass'
+          index = @connection.indexes('ex').find { |idx| idx.name == 'with_opclass' }
+          assert_equal 'data varchar_pattern_ops', index.columns
+        end
+      end
+
       def test_columns_for_distinct_zero_orders
         assert_equal "posts.id",
           @connection.columns_for_distinct("posts.id", [])
diff --git a/activerecord/test/cases/adapters/postgresql/schema_test.rb b/activerecord/test/cases/adapters/postgresql/schema_test.rb
index 00ebabc9c5..52ef07f654 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_test.rb
@@ -325,7 +325,7 @@ class SchemaTest < ActiveRecord::PostgreSQLTestCase
 
   def test_dump_indexes_for_table_with_scheme_specified_in_name
     indexes = @connection.indexes("#{SCHEMA_NAME}.#{TABLE_NAME}")
-    assert_equal 4, indexes.size
+    assert_equal 5, indexes.size
   end
 
   def test_with_uppercase_index_name
@@ -449,18 +449,22 @@ class SchemaTest < ActiveRecord::PostgreSQLTestCase
     def do_dump_index_tests_for_schema(this_schema_name, first_index_column_name, second_index_column_name, third_index_column_name, fourth_index_column_name)
       with_schema_search_path(this_schema_name) do
         indexes = @connection.indexes(TABLE_NAME).sort_by(&:name)
-        assert_equal 4,indexes.size
-
-        do_dump_index_assertions_for_one_index(indexes[0], INDEX_A_NAME, first_index_column_name)
-        do_dump_index_assertions_for_one_index(indexes[1], INDEX_B_NAME, second_index_column_name)
-        do_dump_index_assertions_for_one_index(indexes[2], INDEX_D_NAME, third_index_column_name)
-        do_dump_index_assertions_for_one_index(indexes[3], INDEX_E_NAME, fourth_index_column_name)
-
-        indexes.select{|i| i.name != INDEX_E_NAME}.each do |index|
-           assert_equal :btree, index.using
-        end
-        assert_equal :gin, indexes.select{|i| i.name == INDEX_E_NAME}[0].using
-        assert_equal :desc, indexes.select{|i| i.name == INDEX_D_NAME}[0].orders[INDEX_D_COLUMN]
+        assert_equal 5, indexes.size
+
+        index_a, index_b, index_c, index_d, index_e = indexes
+
+        do_dump_index_assertions_for_one_index(index_a, INDEX_A_NAME, first_index_column_name)
+        do_dump_index_assertions_for_one_index(index_b, INDEX_B_NAME, second_index_column_name)
+        do_dump_index_assertions_for_one_index(index_d, INDEX_D_NAME, third_index_column_name)
+        do_dump_index_assertions_for_one_index(index_e, INDEX_E_NAME, fourth_index_column_name)
+
+        assert_equal :btree, index_a.using
+        assert_equal :btree, index_b.using
+        assert_equal :gin,   index_c.using
+        assert_equal :btree, index_d.using
+        assert_equal :gin,   index_e.using
+
+        assert_equal :desc,  index_d.orders[INDEX_D_COLUMN]
       end
     end
 
diff --git a/activerecord/test/cases/schema_dumper_test.rb b/activerecord/test/cases/schema_dumper_test.rb
index 7a304eab7f..f1927f561e 100644
--- a/activerecord/test/cases/schema_dumper_test.rb
+++ b/activerecord/test/cases/schema_dumper_test.rb
@@ -92,7 +92,7 @@ class SchemaDumperTest < ActiveRecord::TestCase
       next if column_set.empty?
 
       lengths = column_set.map do |column|
-        if match = column.match(/\bt\.\w+\s+"/)
+        if match = column.match(/\bt\.\w+\s+(?="\w+?")/)
           match[0].length
         end
       end.compact
@@ -279,6 +279,11 @@ class SchemaDumperTest < ActiveRecord::TestCase
       assert_match %r{t\.decimal\s+"decimal_array_default",\s+default: \["1.23", "3.45"\],\s+array: true}, output
     end
 
+    def test_schema_dump_expression_indices
+      index_definition = standard_dump.split(/\n/).grep(/t\.index.*company_expression_index/).first.strip
+      assert_equal 't.index "lower((name)::text)", name: "company_expression_index", using: :btree', index_definition
+    end
+
     if ActiveRecord::Base.connection.supports_extensions?
       def test_schema_dump_includes_extensions
         connection = ActiveRecord::Base.connection
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 1027bcb365..628a59c2e3 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -199,6 +199,7 @@ ActiveRecord::Schema.define do
     t.index [:firm_id, :type, :rating], name: "company_index"
     t.index [:firm_id, :type], name: "company_partial_index", where: "rating > 10"
     t.index :name, name: 'company_name_index', using: :btree
+    t.index 'lower(name)', name: "company_expression_index" if supports_expression_index?
   end
 
   create_table :content, force: true do |t|