Revert "Add prepared statements support for Mysql2Adapter"

Gemfile

@@ -92,7 +92,7 @@ platforms :ruby do
   group :db do
     gem 'pg', '>= 0.18.0'
     gem 'mysql', '>= 2.9.0'
-    gem 'mysql2', '>= 0.4.2'
+    gem 'mysql2', '>= 0.4.0'
   end
 end
 

Gemfile.lock

@@ -238,7 +238,7 @@ GEM
     multi_json (1.11.2)
     mustache (1.0.2)
     mysql (2.9.1)
-    mysql2 (0.4.2)
+    mysql2 (0.4.1)
     nokogiri (1.6.7.rc3)
       mini_portile (~> 0.7.0.rc4)
     pg (0.18.3)
@@ -347,7 +347,7 @@ DEPENDENCIES
   minitest (< 5.3.4)
   mocha (~> 0.14)
   mysql (>= 2.9.0)
-  mysql2 (>= 0.4.2)
+  mysql2 (>= 0.4.0)
   nokogiri (>= 1.6.7.rc3)
   pg (>= 0.18.0)
   psych (~> 2.0)

activerecord/CHANGELOG.md

@@ -1,7 +1,3 @@
-*   Add prepared statements support for `Mysql2Adapter`.
-
-    *Ryuta Kamizono*
-
 *   Add schema dumping support for PostgreSQL geometric data types.
 
     *Ryuta Kamizono*

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -2,7 +2,6 @@
 require 'active_record/connection_adapters/mysql/schema_creation'
 require 'active_record/connection_adapters/mysql/schema_definitions'
 require 'active_record/connection_adapters/mysql/schema_dumper'
-require 'active_record/connection_adapters/statement_pool'
 
 require 'active_support/core_ext/string/strip'
 
@@ -142,22 +141,13 @@ def attributes_for_hash
       INDEX_TYPES  = [:fulltext, :spatial]
       INDEX_USINGS = [:btree, :hash]
 
-      class StatementPool < ConnectionAdapters::StatementPool
-        private
-
-        def dealloc(stmt)
-          stmt[:stmt].close
-        end
-      end
-
       # FIXME: Make the first parameter more similar for the two adapters
       def initialize(connection, logger, connection_options, config)
         super(connection, logger)
         @connection_options, @config = connection_options, config
         @quoted_column_names, @quoted_table_names = {}, {}
 
         @visitor = Arel::Visitors::MySQL.new self
-        @statements = StatementPool.new(self.class.type_cast_config_to_integer(config.fetch(:statement_limit) { 1000 }))
 
         if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
           @prepared_statements = true
@@ -194,12 +184,6 @@ def supports_bulk_alter? #:nodoc:
         true
       end
 
-      # Returns true, since this connection adapter supports prepared statement
-      # caching.
-      def supports_statement_cache?
-        true
-      end
-
       # Technically MySQL allows to create indexes with the sort order syntax
       # but at the moment (5.5) it doesn't yet implement them
       def supports_index_sort_order?
@@ -407,20 +391,9 @@ def build_footer(nrows, elapsed)
         end
       end
 
-      def select_all(arel, name = nil, binds = [])
-        rows = if ExplainRegistry.collect? && prepared_statements
-          unprepared_statement { super }
-        else
-          super
-        end
-        @connection.next_result while @connection.more_results?
-        rows
-      end
-
-      # Clears the prepared statements cache.
       def clear_cache!
+        super
         reload_type_map
-        @statements.clear
       end
 
       # Executes the SQL statement in the context of this connection.
@@ -431,26 +404,11 @@ def execute(sql, name = nil)
       # MysqlAdapter has to free a result after using it, so we use this method to write
       # stuff in an abstract way without concerning ourselves about whether it needs to be
       # explicitly freed or not.
-      def execute_and_free(sql, name = nil) # :nodoc:
+      def execute_and_free(sql, name = nil) #:nodoc:
         yield execute(sql, name)
       end
 
-      def exec_delete(sql, name, binds) # :nodoc:
-        if without_prepared_statement?(binds)
-          execute_and_free(sql, name) { @connection.affected_rows }
-        else
-          exec_stmt_and_free(sql, name, binds) { |stmt| stmt.affected_rows }
-        end
-      end
-      alias :exec_update :exec_delete
-
-      def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil) # :nodoc:
-        super
-        id_value || last_inserted_id
-      end
-      alias :create :insert_sql
-
-      def update_sql(sql, name = nil) # :nodoc:
+      def update_sql(sql, name = nil) #:nodoc:
         super
         @connection.affected_rows
       end

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -1,6 +1,6 @@
 require 'active_record/connection_adapters/abstract_mysql_adapter'
 
-gem 'mysql2', '>= 0.4.2', '< 0.5'
+gem 'mysql2', '>= 0.3.18', '< 0.5'
 require 'mysql2'
 
 module ActiveRecord
@@ -33,6 +33,7 @@ class Mysql2Adapter < AbstractMysqlAdapter
 
       def initialize(connection, logger, connection_options, config)
         super
+        @prepared_statements = false
         configure_connection
       end
 
@@ -125,13 +126,9 @@ def disconnect!
       # Returns an array of arrays containing the field values.
       # Order is the same as that returned by +columns+.
       def select_rows(sql, name = nil, binds = [])
-        rows = if without_prepared_statement?(binds)
-          execute_and_free(sql, name) { |result| result.to_a }
-        else
-          exec_stmt_and_free(sql, name, binds) { |stmt, result| result.to_a }
-        end
+        result = execute(sql, name)
         @connection.next_result while @connection.more_results?
-        rows
+        result.to_a
       end
 
       # Executes the SQL statement in the context of this connection.
@@ -146,59 +143,35 @@ def execute(sql, name = nil)
       end
 
       def exec_query(sql, name = 'SQL', binds = [], prepare: false)
-        if without_prepared_statement?(binds)
-          execute_and_free(sql, name) do |result|
-            ActiveRecord::Result.new(result.fields, result.to_a) if result
-          end
-        else
-          exec_stmt_and_free(sql, name, binds, cache_stmt: prepare) do |stmt, result|
-            ActiveRecord::Result.new(result.fields, result.to_a) if result
-          end
-        end
-      end
-
-      def last_inserted_id(result = nil)
-        @connection.last_id
+        result = execute(sql, name)
+        @connection.next_result while @connection.more_results?
+        ActiveRecord::Result.new(result.fields, result.to_a)
       end
 
-      private
+      alias exec_without_stmt exec_query
 
-      def exec_stmt_and_free(sql, name, binds, cache_stmt: false)
-        if @connection
-          # make sure we carry over any changes to ActiveRecord::Base.default_timezone that have been
-          # made since we established the connection
-          @connection.query_options[:database_timezone] = ActiveRecord::Base.default_timezone
-        end
-
-        type_casted_binds = binds.map { |attr| type_cast(attr.value_for_database) }
+      def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
+        super
+        id_value || @connection.last_id
+      end
+      alias :create :insert_sql
 
-        log(sql, name, binds) do
-          if !cache_stmt
-            stmt = @connection.prepare(sql)
-          else
-            cache = @statements[sql] ||= {
-              stmt: @connection.prepare(sql)
-            }
-            stmt = cache[:stmt]
-          end
+      def exec_insert(sql, name, binds, pk = nil, sequence_name = nil)
+        execute to_sql(sql, binds), name
+      end
 
-          begin
-            result = stmt.execute(*type_casted_binds)
-          rescue Mysql2::Error => e
-            if !cache_stmt
-              stmt.close
-            else
-              @statements.delete(sql)
-            end
-            raise e
-          end
+      def exec_delete(sql, name, binds)
+        execute to_sql(sql, binds), name
+        @connection.affected_rows
+      end
+      alias :exec_update :exec_delete
 
-          ret = yield stmt, result
-          stmt.close if !cache_stmt
-          ret
-        end
+      def last_inserted_id(result)
+        @connection.last_id
       end
 
+      private
+
       def connect
         @connection = Mysql2::Client.new(@config)
         configure_connection