class ActiveRecord::ConnectionAdapters::AbstractAdapter - activerecord-4.2.4 Documentation

# class ActiveRecord::ConnectionAdapters::AbstractAdapter

Active Record supports multiple database systems. AbstractAdapter and related classes form the abstraction layer which makes this possible. An AbstractAdapter represents a connection to a database, and provides an abstract interface for database-specific functionality such as establishing a connection, escaping values, building the right SQL fragments for ':offset' and ':limit' options, etc.

All the concrete database adapters follow the interface laid down in this class. ActiveRecord::Base.connection returns an AbstractAdapter object, which you can use.

Most of the methods in the adapter are useful during migrations. Most notably, the instance methods provided by SchemaStatement are very useful.

### Constants

ADAPTER_NAME
SIMPLE_INT

### Attributes

in_use?[R]
logger[R]
owner[R]
pool[RW]
prepared_statements[R]
schema_cache[R]
visitor[RW]

### Public Class Methods

type_cast_config_to_boolean(config) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 91
    def self.type_cast_config_to_boolean(config)
      if config == "false"
        false
      else
        config
      end
    end

type_cast_config_to_integer(config) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 83
    def self.type_cast_config_to_integer(config)
      if config =~ SIMPLE_INT
        config.to_i
      else
        config
      end
    end

### Public Instance Methods

active?() click to toggle source

Checks whether the connection to the database is still active. This includes checking whether the database is actually capable of responding, i.e. whether the connection isn't stale.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 284
    def active?
    end

adapter_name() click to toggle source

Returns the human-readable name of the adapter. Use mixed case - one can always use downcase if needed.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 168
    def adapter_name
      self.class::ADAPTER_NAME
    end

case_insensitive_comparison(table, attribute, column, value) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 357
    def case_insensitive_comparison(table, attribute, column, value)
      table[attribute].lower.eq(table.lower(value))
    end

case_sensitive_comparison(table, attribute, column, value) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 351
    def case_sensitive_comparison(table, attribute, column, value)
      table_attr = table[attribute]
      value = case_sensitive_modifier(value, table_attr) unless value.nil?
      table_attr.eq(value)
    end

case_sensitive_modifier(node, table_attribute) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 347
    def case_sensitive_modifier(node, table_attribute)
      node
    end

clear_cache!() click to toggle source

Clear any caching the database adapter may be doing, for example clearing the prepared statement cache. This is database specific.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 315
    def clear_cache!
      # this should be overridden by concrete adapters
    end

close() click to toggle source

Check the connection back in to the connection pool

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 366
    def close
      pool.checkin self
    end

collector() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 126
    def collector
      if prepared_statements
        SQLString.new
      else
        BindCollector.new
      end
    end

create_savepoint(name = nil) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 341
    def create_savepoint(name = nil)
    end

current_savepoint_name() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 361
    def current_savepoint_name
      current_transaction.savepoint_name
    end

disable_extension(name) click to toggle source

This is meant to be implemented by the adapters that support extensions

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 247
    def disable_extension(name)
    end

disable_referential_integrity() { || ... } click to toggle source

Override to turn off referential integrity while executing `&block`.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 275
    def disable_referential_integrity
      yield
    end

disconnect!() click to toggle source

Disconnects from the database if already connected. Otherwise, this method does nothing.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 297
    def disconnect!
      clear_cache!
      reset_transaction
    end

enable_extension(name) click to toggle source

This is meant to be implemented by the adapters that support extensions

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 251
    def enable_extension(name)
    end

expire() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 155
    def expire
      @owner = nil
    end

extensions() click to toggle source

A list of extensions, to be filled in by adapters that support them.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 255
    def extensions
      []
    end

index_algorithms() click to toggle source

A list of index algorithms, to be filled by adapters that support them.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 260
    def index_algorithms
      {}
    end

lease() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 142
    def lease
      synchronize do
        unless in_use?
          @owner = Thread.current
        end
      end
    end

new_column(name, default, cast_type, sql_type = nil, null = true) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 376
    def new_column(name, default, cast_type, sql_type = nil, null = true)
      Column.new(name, default, cast_type, sql_type, null)
    end

prefetch_primary_key?(table_name = nil) click to toggle source

Should primary key values be selected from their corresponding sequence before the insert statement? If true, next_sequence_value is called before each insert to set the record's primary key.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 201
    def prefetch_primary_key?(table_name = nil)
      false
    end

raw_connection() click to toggle source

Provides access to the underlying database driver for this adapter. For example, this method returns a Mysql object in case of MysqlAdapter, and a PGconn object in case of PostgreSQLAdapter.

This is useful for when you need to call a proprietary method such as PostgreSQL's lo_* methods.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 337
    def raw_connection
      @connection
    end

reconnect!() click to toggle source

Disconnects from the database if already connected, and establishes a new connection with the database. Implementors should call super if they override the default implementation.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 290
    def reconnect!
      clear_cache!
      reset_transaction
    end

release_savepoint(name = nil) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 344
    def release_savepoint(name = nil)
    end

requires_reloading?() click to toggle source

Returns true if its required to reload the connection between requests for development mode.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 320
    def requires_reloading?
      false
    end

reset!() click to toggle source

Reset the state of this connection, directing the DBMS to clear transactions and other connection-related server-side state. Usually a database-dependent operation.

The default implementation does nothing; the implementation should be overridden by concrete adapters.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 308
    def reset!
      # this should be overridden by concrete adapters
    end

schema_cache=(cache) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 150
    def schema_cache=(cache)
      cache.connection = self
      @schema_cache = cache
    end

schema_creation() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 138
    def schema_creation
      SchemaCreation.new self
    end

substitute_at(column, _unused = 0) click to toggle source

Returns a bind substitution value given a bind `column` NOTE: The column param is currently being used by the sqlserver-adapter

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 268
    def substitute_at(column, _unused = 0)
      Arel::Nodes::BindParam.new
    end

supports_bulk_alter?() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 189
    def supports_bulk_alter?
      false
    end

supports_ddl_transactions?() click to toggle source

Does this adapter support DDL rollbacks in transactions? That is, would CREATE TABLE or ALTER TABLE get rolled back by a transaction?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 185
    def supports_ddl_transactions?
      false
    end

supports_explain?() click to toggle source

Does this adapter support explain?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 216
    def supports_explain?
      false
    end

supports_extensions?() click to toggle source

Does this adapter support database extensions?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 226
    def supports_extensions?
      false
    end

supports_foreign_keys?() click to toggle source

Does this adapter support creating foreign key constraints?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 237
    def supports_foreign_keys?
      false
    end

supports_index_sort_order?() click to toggle source

Does this adapter support index sort order?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 206
    def supports_index_sort_order?
      false
    end

supports_indexes_in_create?() click to toggle source

Does this adapter support creating indexes in the same statement as creating the table?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 232
    def supports_indexes_in_create?
      false
    end

supports_migrations?() click to toggle source

Does this adapter support migrations?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 173
    def supports_migrations?
      false
    end

supports_partial_index?() click to toggle source

Does this adapter support partial indices?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 211
    def supports_partial_index?
      false
    end

supports_primary_key?() click to toggle source

Can this adapter determine the primary key for tables not attached to an Active Record class, such as join tables?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 179
    def supports_primary_key?
      false
    end

supports_savepoints?() click to toggle source

Does this adapter support savepoints?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 194
    def supports_savepoints?
      false
    end

supports_transaction_isolation?() click to toggle source

Does this adapter support setting the isolation level for a transaction?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 221
    def supports_transaction_isolation?
      false
    end

supports_views?() click to toggle source

Does this adapter support views?

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 242
    def supports_views?
      false
    end

unprepared_statement() { || ... } click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 159
    def unprepared_statement
      old_prepared_statements, @prepared_statements = @prepared_statements, false
      yield
    ensure
      @prepared_statements = old_prepared_statements
    end

valid_type?(type) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 134
    def valid_type?(type)
      true
    end

verify!(*ignored) click to toggle source

Checks whether the connection to the database is still active (i.e. not stale). This is done under the hood by calling `active?`. If the connection is no longer active, then this method will reconnect to the database.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 327
    def verify!(*ignored)
      reconnect! unless active?
    end

### Protected Instance Methods

log(sql, name = "SQL", binds = [], statement_name = nil) { || ... } click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 466
    def log(sql, name = "SQL", binds = [], statement_name = nil)
      @instrumenter.instrument(
        "sql.active_record",
        :sql            => sql,
        :name           => name,
        :connection_id  => object_id,
        :statement_name => statement_name,
        :binds          => binds) { yield }
    rescue => e
      raise translate_exception_class(e, sql)
    end

translate_exception(exception, message) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 478
    def translate_exception(exception, message)
      # override in derived class
      ActiveRecord::StatementInvalid.new(message, exception)
    end

translate_exception_class(e, sql) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 453
    def translate_exception_class(e, sql)
      begin
        message = "#{e.class.name}: #{e.message}: #{sql}"
      rescue Encoding::CompatibilityError
        message = "#{e.class.name}: #{e.message.force_encoding sql.encoding}: #{sql}"
      end

      @logger.error message if @logger
      exception = translate_exception(e, message)
      exception.set_backtrace e.backtrace
      exception
    end

without_prepared_statement?(binds) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 483
    def without_prepared_statement?(binds)
      !prepared_statements || binds.empty?
    end