Adds support for concurrent indexing in PostgreSQL adapter

Adds support for algorithm option in MySQL indexes
Moves USING and algorithm options upstream

The syntax is still specific to the Adapter, so the actual executed string happens
in the corresponding adapter

5 files changed, 24 insertions, 14 deletions

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 26cacbde37..35f1112798 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -752,11 +752,13 @@ module ActiveRecord
           index_name   = index_name(table_name, column: column_names)
 
           if Hash === options # legacy support, since this param was a string
-            options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using)
+            options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm)
 
             index_type = options[:unique] ? "UNIQUE" : ""
             index_name = options[:name].to_s if options.key?(:name)
             max_index_length = options.fetch(:internal, false) ? index_name_length : allowed_index_name_length
+            algorithm = index_algorithms[options[:algorithm]]
+            using = "USING #{options[:using]}" if options[:using].present?
 
             if supports_partial_index?
               index_options = options[:where] ? " WHERE #{options[:where]}" : ""
@@ -772,6 +774,7 @@ module ActiveRecord
 
             index_type = options
             max_index_length = allowed_index_name_length
+            algorithm = using = nil
           end
 
           if index_name.length > max_index_length
@@ -782,7 +785,7 @@ module ActiveRecord
           end
           index_columns = quoted_columns_for_index(column_names, options).join(", ")
 
-          [index_name, index_type, index_columns, index_options]
+          [index_name, index_type, index_columns, index_options, algorithm, using]
         end
 
         def index_name_for_remove(table_name, options = {})
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 0f4ab68b61..1915c444ef 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -282,6 +282,13 @@ module ActiveRecord
         []
       end
 
+      # A list of index algorithms, to be filled by adapters that
+      # support them. MySQL and PostgreSQL has support for them right
+      # now.
+      def index_algorithms
+        {}
+      end
+
       # QUOTING ==================================================
 
       # Returns a bind substitution value given a +column+ and list of current
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
index 71f5c8fd29..ff3e9acfac 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
@@ -208,6 +208,10 @@ module ActiveRecord
         NATIVE_DATABASE_TYPES
       end
 
+      def index_algorithms
+        { default: 'ALGORITHM = DEFAULT', copy: 'ALGORITHM = COPY', inplace: 'ALGORITHM = INPLACE' }
+      end
+
       # HELPER METHODS ===========================================
 
       # The two drivers have slightly different ways of yielding hashes of results, so
@@ -506,12 +510,8 @@ module ActiveRecord
       end
 
       def add_index(table_name, column_name, options = {}) #:nodoc:
-        if options.is_a?(Hash) && options[:using]
-          index_name, index_type, index_columns, index_options = add_index_options(table_name, column_name, options)
-          execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} USING #{options[:using]} ON #{quote_table_name(table_name)} (#{index_columns})#{index_options}"
-        else
-          super
-        end
+        index_name, index_type, index_columns, index_options, index_algorithm, index_using = add_index_options(table_name, column_name, options)
+        execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} #{index_using} ON #{quote_table_name(table_name)} (#{index_columns})#{index_options} #{index_algorithm}"
       end
 
       # Maps logical Rails types to MySQL-specific data types.
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 688bf1774b..0e1afbae8d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -410,12 +410,8 @@ module ActiveRecord
         end
 
         def add_index(table_name, column_name, options = {}) #:nodoc:
-          if options.is_a?(Hash) && options[:using]
-            index_name, index_type, index_columns, index_options = add_index_options(table_name, column_name, options)
-            execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} USING #{options[:using]} (#{index_columns})#{index_options}"
-          else
-             super
-          end
+          index_name, index_type, index_columns, index_options, index_algorithm, index_using = add_index_options(table_name, column_name, options)
+          execute "CREATE #{index_type} INDEX #{index_algorithm} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} #{index_using} (#{index_columns})#{index_options}"
         end
 
         def remove_index!(table_name, index_name) #:nodoc:
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index d26b676335..46e41e6b48 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -433,6 +433,10 @@ module ActiveRecord
         true
       end
 
+      def index_algorithms
+        { concurrently: 'CONCURRENTLY' }
+      end
+
       class StatementPool < ConnectionAdapters::StatementPool
         def initialize(connection, max)
           super