Class: ActiveRecord::ConnectionAdapters::AbstractAdapter

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

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: SchemaCreation, Version

Constant Summary collapse

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

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 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

#lookup_cast_type_from_column, #quote, #quote_column_name, #quote_default_expression, #quote_string, #quote_table_name, #quote_table_name_for_assignment, #quoted_binary, #quoted_date, #quoted_false, #quoted_time, #quoted_true, #type_cast, #type_cast_from_column, #type_casted_binds, #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, #insert_fixtures, #insert_fixtures_set, #join_to_update, #query, #query_value, #query_values, #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_schema_dumper, #create_table, #data_source_exists?, #data_sources, #drop_join_table, #drop_table, #dump_schema_information, #foreign_key_column_for, #foreign_key_exists?, #foreign_key_options, #foreign_keys, #index_exists?, #index_name, #index_name_exists?, #indexes, #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

Constructor Details

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

:nodoc:

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 101

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

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

  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

#lock ⇒ Object (readonly)

Returns the value of attribute lock.


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

def lock
  @lock
end

#logger ⇒ Object (readonly)

Returns the value of attribute logger.


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

def logger
  @logger
end

#owner ⇒ Object (readonly) Also known as: in_use?

Returns the value of attribute owner.


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

def owner
  @owner
end

#pool ⇒ Object

Returns the value of attribute pool.


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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 79

def pool
  @pool
end

#prepared_statements ⇒ Object (readonly)

Returns the value of attribute prepared_statements.


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

def prepared_statements
  @prepared_statements
end

#schema_cache ⇒ Object

Returns the value of attribute schema_cache.


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

def schema_cache
  @schema_cache
end

#visitor ⇒ Object

Returns the value of attribute visitor.


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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 79

def visitor
  @visitor
end

Class Method Details

.type_cast_config_to_boolean(config) ⇒ Object

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 93

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 83

def self.type_cast_config_to_integer(config)
  if config.is_a?(Integer)
    config
  elsif 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.

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 380

def active?
end

#adapter_name ⇒ Object

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

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

def adapter_name
  self.class::ADAPTER_NAME
end

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

:nodoc:

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 454

def case_insensitive_comparison(table, attribute, column, value) # :nodoc:
  if can_perform_case_insensitive_comparison_for?(column)
    table[attribute].lower.eq(table.lower(value))
  else
    table[attribute].eq(value)
  end
end

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

:nodoc:

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 450

def case_sensitive_comparison(table, attribute, column, value) # :nodoc:
  table[attribute].eq(value)
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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 424

def clear_cache!
  # this should be overridden by concrete adapters
end

#close ⇒ Object

Check the connection back in to the connection pool

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

def close
  pool.checkin self
end

#column_name_for_operation(operation, node) ⇒ Object

:nodoc:

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

def column_name_for_operation(operation, node) # :nodoc:
  column_name_from_arel_node(node)
end

#column_name_from_arel_node(node) ⇒ Object

:nodoc:

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

def column_name_from_arel_node(node) # :nodoc:
  visitor.accept(node, Arel::Collectors::SQLString.new).value
end

#default_index_type?(index) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 480

def default_index_type?(index) # :nodoc:
  index.using.nil?
end

#disable_extension(name) ⇒ Object

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

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 337

def disable_extension(name)
end

#disable_referential_integrity ⇒ Object

Override to turn off referential integrity while executing &block.

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 371

def disable_referential_integrity
  yield
end

#discard! ⇒ Object

Immediately forget this connection ever existed. Unlike disconnect!, this will not communicate with the server.

After calling this method, the behavior of all other methods becomes undefined. This is called internally just before a forked process gets rid of a connection that belonged to its parent.

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 404

def discard!
  # This should be overridden by concrete adapters.
  #
  # Prevent @connection's finalizer from touching the socket, or
  # otherwise communicating with its server, when it is collected.
end

#disconnect! ⇒ Object

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

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 393

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 341

def enable_extension(name)
end

#expire ⇒ Object

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

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 170

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

    @idle_since = Concurrent.monotonic_time
    @owner = nil
  else
    raise ActiveRecordError, "Cannot expire connection, it is not currently leased."
  end
end

#extensions ⇒ Object

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

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 359

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 348

def get_advisory_lock(lock_id) # :nodoc:
end

#index_algorithms ⇒ Object

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

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 364

def index_algorithms
  {}
end

#lease ⇒ Object

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

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 149

def lease
  if in_use?
    msg = "Cannot lease connection, ".dup
    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

#migration_context ⇒ Object

:nodoc:

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 128

def migration_context # :nodoc:
  MigrationContext.new(migrations_paths)
end

#migrations_paths ⇒ Object

:nodoc:

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 124

def migrations_paths # :nodoc:
  @config[:migrations_paths] || Migrator.migrations_paths
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.

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 240

def prefetch_primary_key?(table_name = nil)
  false
end

#raw_connection ⇒ Object

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 PG::Connection 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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 446

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 386

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 355

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.

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 429

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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 417

def reset!
  # this should be overridden by concrete adapters
end

#seconds_idle ⇒ Object

Seconds since this connection was returned to the pool

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 199

def seconds_idle # :nodoc:
  return 0 if in_use?
  Concurrent.monotonic_time - @idle_since
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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 186

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?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 233

def supports_advisory_locks?
  false
end

#supports_bulk_alter? ⇒ Boolean

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 223

def supports_bulk_alter?
  false
end

#supports_comments? ⇒ Boolean

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

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 312

def supports_comments?
  false
end

#supports_comments_in_create? ⇒ Boolean

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

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 317

def supports_comments_in_create?
  false
end

#supports_datetime_with_precision? ⇒ Boolean

Does this adapter support datetime with precision?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 302

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?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 219

def supports_ddl_transactions?
  false
end

#supports_explain? ⇒ Boolean

Does this adapter support explain?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 260

def supports_explain?
  false
end

#supports_expression_index? ⇒ Boolean

Does this adapter support expression indices?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 255

def supports_expression_index?
  false
end

#supports_extensions? ⇒ Boolean

Does this adapter support database extensions?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 270

def supports_extensions?
  false
end

#supports_foreign_keys? ⇒ Boolean

Does this adapter support creating foreign key constraints?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 281

def supports_foreign_keys?
  false
end

#supports_foreign_tables? ⇒ Boolean

Does this adapter support foreign/external tables?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 332

def supports_foreign_tables?
  false
end

#supports_index_sort_order? ⇒ Boolean

Does this adapter support index sort order?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 245

def supports_index_sort_order?
  false
end

#supports_json? ⇒ Boolean

Does this adapter support json data type?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 307

def supports_json?
  false
end

#supports_multi_insert? ⇒ Boolean

Does this adapter support multi-value insert?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 322

def supports_multi_insert?
  true
end

#supports_partial_index? ⇒ Boolean

Does this adapter support partial indices?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 250

def supports_partial_index?
  false
end

#supports_savepoints? ⇒ Boolean

Does this adapter support savepoints?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 228

def supports_savepoints?
  false
end

#supports_transaction_isolation? ⇒ Boolean

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

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 265

def supports_transaction_isolation?
  false
end

#supports_validate_constraints? ⇒ Boolean

Does this adapter support creating invalid constraints?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 286

def supports_validate_constraints?
  false
end

#supports_views? ⇒ Boolean

Does this adapter support views?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 297

def supports_views?
  false
end

#supports_virtual_columns? ⇒ Boolean

Does this adapter support virtual columns?

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 327

def supports_virtual_columns?
  false
end

#unprepared_statement ⇒ Object

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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 204

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

#valid_type?(type) ⇒ Boolean

:nodoc:

Returns:

  • (Boolean)
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# File 'lib/active_record/connection_adapters/abstract_adapter.rb', line 144

def valid_type?(type) # :nodoc:
  !native_database_types[type].nil?
end

#verify! ⇒ 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 'lib/active_record/connection_adapters/abstract_adapter.rb', line 436

def verify!
  reconnect! unless active?
end