Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

Inherits:
Object
  • Object
show all
Includes:
ColumnDumper, DatabaseLimits, DatabaseStatements, QueryCache, Quoting, Savepoints, SchemaStatements, ActiveSupport::Callbacks
Defined in:
activerecord/lib/active_record/connection_adapters/abstract_adapter.rb,
activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb

Overview

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 SchemaStatements are very useful.

Defined Under Namespace

Classes: BindCollector, SQLString, SchemaCreation, Version

Constant Summary collapse

ADAPTER_NAME =
"Abstract".freeze
SIMPLE_INT =
/\A\d+\z/

Constants included from ActiveSupport::Callbacks

ActiveSupport::Callbacks::CALLBACK_FILTER_TYPES

Instance Attribute Summary collapse

Attributes included from QueryCache

#query_cache, #query_cache_enabled

Attributes included from DatabaseStatements

#transaction_manager

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Savepoints

#create_savepoint, #current_savepoint_name, #exec_rollback_to_savepoint, #release_savepoint

Methods included from ColumnDumper

#column_spec, #column_spec_for_primary_key, #migration_keys, #prepare_column_options

Methods included from QueryCache

#cache, #clear_query_cache, dirties_query_cache, #disable_query_cache!, #enable_query_cache!, included, #select_all, #uncached

Methods included from DatabaseLimits

#allowed_index_name_length, #column_name_length, #columns_per_multicolumn_index, #columns_per_table, #in_clause_length, #index_name_length, #indexes_per_table, #joins_per_query, #sql_query_length, #table_alias_length, #table_name_length

Methods included from Quoting

#fetch_type_metadata, #lookup_cast_type_from_column, #prepare_binds_for_database, #quote, #quote_column_name, #quote_default_expression, #quote_string, #quote_table_name, #quote_table_name_for_assignment, #quoted_date, #quoted_false, #quoted_time, #quoted_true, #type_cast, #type_cast_from_column, #unquoted_false, #unquoted_true

Methods included from DatabaseStatements

#add_transaction_record, #begin_db_transaction, #begin_isolated_db_transaction, #cacheable_query, #commit_db_transaction, #default_sequence_name, #delete, #empty_insert_statement_value, #exec_delete, #exec_insert, #exec_query, #exec_rollback_db_transaction, #exec_update, #execute, #insert, #insert_fixture, #join_to_update, #reset_sequence!, #reset_transaction, #rollback_db_transaction, #rollback_to_savepoint, #sanitize_limit, #select_all, #select_one, #select_rows, #select_value, #select_values, #supports_statement_cache?, #to_sql, #transaction, #transaction_isolation_levels, #transaction_open?, #transaction_state, #truncate, #update

Methods included from SchemaStatements

#add_column, #add_foreign_key, #add_index, #add_index_options, #add_reference, #add_timestamps, #assume_migrated_upto_version, #change_column, #change_column_comment, #change_column_default, #change_column_null, #change_table, #change_table_comment, #column_exists?, #columns, #columns_for_distinct, #create_join_table, #create_table, #data_source_exists?, #data_sources, #drop_join_table, #drop_table, #dump_schema_information, #foreign_key_column_for, #foreign_key_exists?, #foreign_key_for, #foreign_key_for!, #foreign_key_options, #foreign_keys, #index_exists?, #index_name, #index_name_exists?, #initialize_internal_metadata_table, #initialize_schema_migrations_table, #insert_versions_sql, #internal_string_options_for_primary_key, #native_database_types, #options_include_default?, #primary_key, #remove_column, #remove_columns, #remove_foreign_key, #remove_index, #remove_reference, #remove_timestamps, #rename_column, #rename_index, #rename_table, #table_alias_for, #table_comment, #table_exists?, #table_options, #tables, #type_to_sql, #update_table_definition, #view_exists?, #views

Methods included from ActiveSupport::Callbacks

#run_callbacks

Methods included from ActiveSupport::Concern

#append_features, #class_methods, extended, #included

Constructor Details

#initialize(connection, logger = nil, config = {}) ⇒ AbstractAdapter

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 98

def initialize(connection, logger = nil, config = {}) # :nodoc:
  super()

  @connection          = connection
  @owner               = nil
  @instrumenter        = ActiveSupport::Notifications.instrumenter
  @logger              = logger
  @config              = config
  @pool                = nil
  @schema_cache        = SchemaCache.new self
  @quoted_column_names, @quoted_table_names = {}, {}
  @visitor             = arel_visitor

  if self.class.type_cast_config_to_boolean(config.fetch(:prepared_statements) { true })
    @prepared_statements = true
    @visitor.extend(DetermineIfPreparableVisitor)
  else
    @prepared_statements = false
  end
end

Instance Attribute Details

#loggerObject (readonly)

Returns the value of attribute logger


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 77

def logger
  @logger
end

#ownerObject (readonly) Also known as: in_use?

Returns the value of attribute owner


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 77

def owner
  @owner
end

#poolObject

Returns the value of attribute pool


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 76

def pool
  @pool
end

#prepared_statementsObject (readonly)

Returns the value of attribute prepared_statements


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 96

def prepared_statements
  @prepared_statements
end

#schema_cacheObject

Returns the value of attribute schema_cache


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 77

def schema_cache
  @schema_cache
end

#visitorObject

Returns the value of attribute visitor


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 76

def visitor
  @visitor
end

Class Method Details

.type_cast_config_to_boolean(config) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 88

def self.type_cast_config_to_boolean(config)
  if config == "false"
    false
  else
    config
  end
end

.type_cast_config_to_integer(config) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 80

def self.type_cast_config_to_integer(config)
  if config =~ SIMPLE_INT
    config.to_i
  else
    config
  end
end

Instance Method Details

#active?Boolean

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 379

def active?
end

#adapter_nameObject

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 222

def adapter_name
  self.class::ADAPTER_NAME
end

#arel_visitorObject

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 152

def arel_visitor # :nodoc:
  Arel::Visitors::ToSql.new(self)
end

#case_insensitive_comparison(table, attribute, column, value) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 444

def case_insensitive_comparison(table, attribute, column, value)
  if can_perform_case_insensitive_comparison_for?(column)
    table[attribute].lower.eq(table.lower(Arel::Nodes::BindParam.new))
  else
    table[attribute].eq(Arel::Nodes::BindParam.new)
  end
end

#case_sensitive_comparison(table, attribute, column, value) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 436

def case_sensitive_comparison(table, attribute, column, value)
  if value.nil?
    table[attribute].eq(value)
  else
    table[attribute].eq(Arel::Nodes::BindParam.new)
  end
end

#clear_cache!Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 410

def clear_cache!  # this should be overridden by concrete adapters

end

#closeObject

Check the connection back in to the connection pool


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 458

def close
  pool.checkin self
end

#collectorObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 144

def collector
  if prepared_statements
    SQLString.new
  else
    BindCollector.new
  end
end

#column_name_for_operation(operation, node) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 476

def column_name_for_operation(operation, node) # :nodoc:
  visitor.accept(node, collector).value
end

#combine_bind_parameters(from_clause: [], join_clause: [], where_clause: [], having_clause: [], limit: nil, offset: nil) ⇒ Object


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 480

def combine_bind_parameters(
  from_clause: [],
  join_clause: [],
  where_clause: [],
  having_clause: [],
  limit: nil,
  offset: nil
) # :nodoc:
  result = from_clause + join_clause + where_clause + having_clause
  if limit
    result << limit
  end
  if offset
    result << offset
  end
  result
end

#disable_extension(name) ⇒ Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 336

def disable_extension(name)
end

#disable_referential_integrityObject

Override to turn off referential integrity while executing &block.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 370

def disable_referential_integrity
  yield
end

#disconnect!Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 392

def disconnect!
  clear_cache!
  reset_transaction
end

#enable_extension(name) ⇒ Object

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 340

def enable_extension(name)
end

#expireObject

this method must only be called while holding connection pool's mutex


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 186

def expire
  if in_use?
    if @owner != Thread.current
      raise ActiveRecordError, "Cannot expire connection, " <<
        "it is owned by a different thread: #{@owner}. " <<
        "Current thread: #{Thread.current}."
    end

    @owner = nil
  else
    raise ActiveRecordError, 'Cannot expire connection, it is not currently leased.'
  end
end

#extensionsObject

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 358

def extensions
  []
end

#get_advisory_lock(lock_id) ⇒ Object

This is meant to be implemented by the adapters that support advisory locks

Return true if we got the lock, otherwise false


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 347

def get_advisory_lock(lock_id) # :nodoc:
end

#index_algorithmsObject

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 363

def index_algorithms
  {}
end

#leaseObject

this method must only be called while holding connection pool's mutex


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 165

def lease
  if in_use?
    msg = 'Cannot lease connection, '
    if @owner == Thread.current
      msg << 'it is already leased by the current thread.'
    else
      msg << "it is already in use by a different thread: #{@owner}. " <<
             "Current thread: #{Thread.current}."
    end
    raise ActiveRecordError, msg
  end

  @owner = Thread.current
end

#lookup_cast_type(sql_type) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 472

def lookup_cast_type(sql_type) # :nodoc:
  type_map.lookup(sql_type)
end

#new_column(name, default, sql_type_metadata, null, table_name, default_function = nil, collation = nil) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 468

def new_column(name, default, , null, table_name, default_function = nil, collation = nil) # :nodoc:
  Column.new(name, default, , null, table_name, default_function, collation)
end

#prefetch_primary_key?(table_name = nil) ⇒ Boolean

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 260

def prefetch_primary_key?(table_name = nil)
  false
end

#raw_connectionObject

Provides access to the underlying database driver for this adapter. For example, this method returns a Mysql2::Client object in case of Mysql2Adapter, 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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 432

def raw_connection
  @connection
end

#reconnect!Object

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 385

def reconnect!
  clear_cache!
  reset_transaction
end

#release_advisory_lock(lock_id) ⇒ Object

This is meant to be implemented by the adapters that support advisory locks.

Return true if we released the lock, otherwise false


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 354

def release_advisory_lock(lock_id) # :nodoc:
end

#requires_reloading?Boolean

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 415

def requires_reloading?
  false
end

#reset!Object

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 403

def reset!  # this should be overridden by concrete adapters

end

#schema_creationObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 160

def schema_creation
  SchemaCreation.new self
end

#steal!Object

this method must only be called while holding connection pool's mutex (and a desire for segfaults)


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 201

def steal! # :nodoc:
  if in_use?
    if @owner != Thread.current
      pool.send :remove_connection_from_thread_cache, self, @owner

      @owner = Thread.current
    end
  else
    raise ActiveRecordError, 'Cannot steal connection, it is not currently leased.'
  end
end

#supports_advisory_locks?Boolean

Does this adapter support application-enforced advisory locking?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 253

def supports_advisory_locks?
  false
end

#supports_bulk_alter?Boolean


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 243

def supports_bulk_alter?
  false
end

#supports_comments?Boolean

Does this adapter support metadata comments on database objects (tables, columns, indexes)?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 321

def supports_comments?
  false
end

#supports_comments_in_create?Boolean

Can comments for tables, columns, and indexes be specified in create/alter table statements?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 326

def supports_comments_in_create?
  false
end

#supports_datetime_with_precision?Boolean

Does this adapter support datetime with precision?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 311

def supports_datetime_with_precision?
  false
end

#supports_ddl_transactions?Boolean

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 239

def supports_ddl_transactions?
  false
end

#supports_explain?Boolean

Does this adapter support explain?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 280

def supports_explain?
  false
end

#supports_expression_index?Boolean

Does this adapter support expression indices?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 275

def supports_expression_index?
  false
end

#supports_extensions?Boolean

Does this adapter support database extensions?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 290

def supports_extensions?
  false
end

#supports_index_sort_order?Boolean

Does this adapter support index sort order?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 265

def supports_index_sort_order?
  false
end

#supports_json?Boolean

Does this adapter support json data type?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 316

def supports_json?
  false
end

#supports_migrations?Boolean

Does this adapter support migrations?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 227

def supports_migrations?
  false
end

#supports_multi_insert?Boolean

Does this adapter support multi-value insert?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 331

def supports_multi_insert?
  true
end

#supports_partial_index?Boolean

Does this adapter support partial indices?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 270

def supports_partial_index?
  false
end

#supports_primary_key?Boolean

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 233

def supports_primary_key?
  false
end

#supports_savepoints?Boolean

Does this adapter support savepoints?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 248

def supports_savepoints?
  false
end

#supports_transaction_isolation?Boolean

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 285

def supports_transaction_isolation?
  false
end

#supports_views?Boolean

Does this adapter support views?


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 306

def supports_views?
  false
end

#type_mapObject

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 462

def type_map # :nodoc:
  @type_map ||= Type::TypeMap.new.tap do |mapping|
    initialize_type_map(mapping)
  end
end

#unprepared_statementObject


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 213

def unprepared_statement
  old_prepared_statements, @prepared_statements = @prepared_statements, false
  yield
ensure
  @prepared_statements = old_prepared_statements
end

#valid_type?(type) ⇒ Boolean


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 156

def valid_type?(type)
  false
end

#verify!(*ignored) ⇒ Object

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract_adapter.rb', line 422

def verify!(*ignored)
  reconnect! unless active?
end