ActiveRecord::ConnectionAdapters::AbstractAdapter (original) (raw)

Active Record Abstract Adapter

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.lease_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.

Namespace

Methods

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Included Modules

Constants

ADAPTER_NAME = "Abstract"
COMMENT_REGEX = %r{(?:--.*\n)|/\*(?:[^*]
EXTENDED_TYPE_MAPS = Concurrent::Map.new
SIMPLE_INT = /\A\d+\z/
TYPE_MAP = Type::TypeMap.new.tap { |m

Attributes

[R] in_use?
[R] lock
[R] logger
[R] owner
[R] pool
[R] visitor

Class Public methods

Does the database for this adapter exist?

Source: show | on GitHub

def self.database_exists?(config) new(config).database_exists? end

dbconsole(config, options = {})Link

Opens a database console session.

Source: show | on GitHub

def self.dbconsole(config, options = {}) raise NotImplementedError end

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def self.find_cmd_and_exec(commands, *args) commands = Array(commands)

dirs_on_path = ENV["PATH"].to_s.split(File::PATH_SEPARATOR) unless (ext = RbConfig::CONFIG["EXEEXT"]).empty? commands = commands.map { |cmd| "#{cmd}#{ext}" } end

full_path_command = nil found = commands.detect do |cmd| dirs_on_path.detect do |path| full_path_command = File.join(path, cmd) begin stat = File.stat(full_path_command) rescue SystemCallError else stat.file? && stat.executable? end end end

if found exec full_path_command, *args else abort("Couldn't find database client: #{commands.join(', ')}. Check your $PATH and try again.") end end

Source: show | on GitHub

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

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def self.type_cast_config_to_integer(config) if config.is_a?(Integer) config elsif SIMPLE_INT.match?(config) config.to_i else config end end

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def self.validate_default_timezone(config) case config when nil when "utc", "local" config.to_sym else raise ArgumentError, "default_timezone must be either 'utc' or 'local'" end end

Instance Public methods

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

Source: show | on GitHub

def adapter_name self.class::ADAPTER_NAME end

Override to check all foreign key constraints in a database. The adapter should raise a ActiveRecord::StatementInvalid if foreign key constraints are not met.

Clear any caching the database adapter may be doing.

Source: show | on GitHub

def clear_cache!(new_connection: false) if @statements @lock.synchronize do if new_connection @statements.reset else @statements.clear end end end end

Check the connection back in to the connection pool

Checks whether the connection to the database was established. This doesn’t include checking whether the database is actually capable of responding, i.e. whether the connection is stale.

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def connected? !@raw_connection.nil? end

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def connection_retries (@config[:connection_retries] || 1).to_i end

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def database_exists? connect! true rescue ActiveRecord::NoDatabaseError false end

Source: show | on GitHub

def default_timezone @default_timezone || ActiveRecord.default_timezone end

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

Override to turn off referential integrity while executing &block.

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def disable_referential_integrity yield end

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.

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

Source: show | on GitHub

def disconnect! @lock.synchronize do clear_cache!(new_connection: true) reset_transaction @raw_connection_dirty = false end end

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

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

Source: show | on GitHub

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

@idle_since = Process.clock_gettime(Process::CLOCK_MONOTONIC)
@owner = nil

else raise ActiveRecordError, "Cannot expire connection, it is not currently leased." end end

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

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

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

Source: show | on GitHub

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

@owner = ActiveSupport::IsolatedExecutionState.context end

Source: show | on GitHub

def pool=(value) return if value.eql?(@pool) @schema_cache = nil @pool = value end

prefetch_primary_key?(table_name = nil)Link

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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def prefetch_primary_key?(table_name = nil) false end

Source: show | on GitHub

def prepared_statements? @prepared_statements && !prepared_statements_disabled_cache.include?(object_id) end

Determines whether writes are currently being prevented.

Returns true if the connection is a replica or returns the value of current_preventing_writes.

Source: show | on GitHub

def preventing_writes? return true if replica? return false if connection_descriptor.nil?

connection_descriptor.current_preventing_writes end

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.

Active Record cannot track if the database is getting modified using this client. If that is the case, generally you’ll want to invalidate the query cache using ActiveRecord::Base.clear_query_cache.

Source: show | on GitHub

def raw_connection with_raw_connection do |conn| disable_lazy_transactions! @raw_connection_dirty = true conn end end

Disconnects from the database if already connected, and establishes a new connection with the database. Implementors should define private reconnect instead.

Source: show | on GitHub

def reconnect!(restore_transactions: false) retries_available = connection_retries deadline = retry_deadline && Process.clock_gettime(Process::CLOCK_MONOTONIC) + retry_deadline

@lock.synchronize do reconnect

enable_lazy_transactions!
@raw_connection_dirty = false
@last_activity = Process.clock_gettime(Process::CLOCK_MONOTONIC)
@verified = true

reset_transaction(restore: restore_transactions) do
  clear_cache!(new_connection: true)
  attempt_configure_connection
end

rescue => original_exception translated_exception = translate_exception_class(original_exception, nil, nil) retry_deadline_exceeded = deadline && deadline < Process.clock_gettime(Process::CLOCK_MONOTONIC)

if !retry_deadline_exceeded && retries_available > 0
  retries_available -= 1

  if retryable_connection_error?(translated_exception)
    backoff(connection_retries - retries_available)
    retry
  end
end

@last_activity = nil
@verified = false

raise translated_exception

end end

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

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

If a database driver or protocol does not support such a feature, implementors may alias this to reconnect!. Otherwise, implementors should call super immediately after resetting the connection (and while still holding @lock).

Source: show | on GitHub

def reset! clear_cache!(new_connection: true) reset_transaction attempt_configure_connection end

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def retry_deadline if @config[:retry_deadline] @config[:retry_deadline].to_f else nil end end

The role (e.g. :writing) for the current connection. In a non-multi role application, :writing is returned.

Do TransactionRollbackErrors on savepoints affect the parent transaction?

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def savepoint_errors_invalidate_transactions? false end

Source: show | on GitHub

def schema_cache @pool.schema_cache || (@schema_cache ||= BoundSchemaReflection.for_lone_connection(@pool.schema_reflection, self)) end

Returns the version identifier of the schema currently available in the database. This is generally equal to the number of the highest- numbered migration that has been executed, or 0 if no schema information is present / the database is empty.

Source: show | on GitHub

def schema_version pool.migration_context.current_version end

The shard (e.g. :default) for the current connection. In a non-sharded application, :default is returned.

Does this adapter support application-enforced advisory locking?

Does this adapter support creating check constraints?

Source: show | on GitHub

def supports_check_constraints? false end

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

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

Source: show | on GitHub

def supports_common_table_expressions? false end

Source: show | on GitHub

def supports_concurrent_connections? true end

Does this adapter support datetime with precision?

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def supports_datetime_with_precision? false end

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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def supports_ddl_transactions? false end

Does this adapter support creating deferrable constraints?

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def supports_deferrable_constraints? false end

Does this adapter support creating exclusion constraints?

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def supports_exclusion_constraints? false end

Does this adapter support explain?

Does this adapter support expression indices?

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def supports_expression_index? false end

Does this adapter support database extensions?

Does this adapter support creating foreign key constraints?

Does this adapter support foreign/external tables?

Does this adapter support including non-key columns?

Does this adapter support index sort order?

Source: show | on GitHub

def supports_index_sort_order? false end

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

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def supports_indexes_in_create? false end

Source: show | on GitHub

def supports_insert_conflict_target? false end

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def supports_insert_on_duplicate_skip? false end

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def supports_insert_on_duplicate_update? false end

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def supports_insert_returning? false end

Does this adapter support JSON data type?

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def supports_lazy_transactions? false end

Does this adapter support materialized views?

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def supports_materialized_views? false end

Source: show | on GitHub

def supports_nulls_not_distinct? false end

Does this adapter support optimizer hints?

Does this adapter support partial indices?

Source: show | on GitHub

def supports_partitioned_indexes? false end

Source: show | on GitHub

def supports_restart_db_transaction? false end

Does this adapter support savepoints?

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

Source: show | on GitHub

def supports_transaction_isolation? false end

Does this adapter support creating unique constraints?

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def supports_unique_constraints? false end

Does this adapter support creating invalid constraints?

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def supports_validate_constraints? false end

Does this adapter support views?

Does this adapter support virtual columns?

Removes the connection from the pool and disconnect it.

Source: show | on GitHub

def throw_away! pool.remove self disconnect! end

Source: show | on GitHub

def unprepared_statement cache = prepared_statements_disabled_cache.add?(object_id) if @prepared_statements yield ensure cache&.delete(object_id) end

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.

Source: show | on GitHub

def verify! unless active? @lock.synchronize do if @unconfigured_connection @raw_connection = @unconfigured_connection @unconfigured_connection = nil attempt_configure_connection @last_activity = Process.clock_gettime(Process::CLOCK_MONOTONIC) @verified = true return end

  reconnect!(restore_transactions: true)
end

end

@verified = true end

Source: show | on GitHub

def verify_timeout (@config[:verify_timeout] || 2).to_i end

Instance Private methods

log(sql, name = "SQL", binds = [], type_casted_binds = [], async: false, &block)Link

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def log(sql, name = "SQL", binds = [], type_casted_binds = [], async: false, &block) instrumenter.instrument( "sql.active_record", sql: sql, name: name, binds: binds, type_casted_binds: type_casted_binds, async: async, connection: self, transaction: current_transaction.user_transaction.presence, row_count: 0, &block ) rescue ActiveRecord::StatementInvalid => ex raise ex.set_query(sql, binds) end