### Home Classes Methods

### In Files

- lib/active_record/connection_adapters/abstract_adapter.rb

### Parent

Object

### Methods

- #active?
- #adapter_name
- #case_insensitive_comparison
- #case_sensitive_modifier
- #clear_cache!
- #close
- #create_savepoint
- #current_savepoint_name
- #decrement_open_transactions
- #disable_referential_integrity
- #disconnect!
- #expire
- #increment_open_transactions
- #lease
- #log
- #prefetch_primary_key?
- #quote_table_name
- #raw_connection
- #reconnect!
- #release_savepoint
- #requires_reloading?
- #reset!
- #rollback_to_savepoint
- #substitute_at
- #supports_bulk_alter?
- #supports_count_distinct?
- #supports_ddl_transactions?
- #supports_explain?
- #supports_index_sort_order?
- #supports_migrations?
- #supports_primary_key?
- #supports_savepoints?
- #transaction_joinable=
- #translate_exception
- #verify!

### Included Modules

- ActiveRecord::ConnectionAdapters::Quoting
- ActiveRecord::ConnectionAdapters::DatabaseStatements
- ActiveRecord::ConnectionAdapters::SchemaStatements
- ActiveRecord::ConnectionAdapters::DatabaseLimits
- ActiveRecord::ConnectionAdapters::QueryCache
- ActiveSupport::Callbacks
- MonitorMixin

### Files

- README.rdoc

### Class/Module Index

Quicksearch

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No matching classes.

# 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.

### Attributes

in_use[R]
in_use?[R]
last_use[R]
logger[R]
open_transactions[R]
pool[RW]
schema_cache[R]
visitor[RW]

### 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 176
    def active?
      @active != false
    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 92
    def adapter_name
      'Abstract'
    end

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

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 259
    def case_insensitive_comparison(table, attribute, column, value)
      table[attribute].lower.eq(table.lower(value))
    end

case_sensitive_modifier(node) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 255
    def case_sensitive_modifier(node)
      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 205
    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 268
    def close
      pool.checkin self
    end

create_savepoint() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 246
    def create_savepoint
    end

current_savepoint_name() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 263
    def current_savepoint_name
      "active_record_#{open_transactions}"
    end

decrement_open_transactions() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 238
    def decrement_open_transactions
      @open_transactions -= 1
    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 167
    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 188
    def disconnect!
      @active = false
    end

expire() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 86
    def expire
      @in_use = false
    end

increment_open_transactions() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 234
    def increment_open_transactions
      @open_transactions += 1
    end

lease() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 77
    def lease
      synchronize do
        unless in_use
          @in_use   = true
          @last_use = Time.now
        end
      end
    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. This is false for all adapters but Firebird.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 136
    def prefetch_primary_key?(table_name = nil)
      false
    end

quote_table_name(name) click to toggle source

Override to return the quoted table name. Defaults to column quoting.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 154
    def quote_table_name(name)
      quote_column_name(name)
    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 228
    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.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 182
    def reconnect!
      @active = true
    end

release_savepoint() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 252
    def release_savepoint
    end

requires_reloading?() click to toggle source

Returns true if its required to reload the connection between requests for development mode. This is not the case for Ruby/MySQL and it's not necessary for any adapters except SQLite.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 211
    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 198
    def reset!
      # this should be overridden by concrete adapters
    end

rollback_to_savepoint() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 249
    def rollback_to_savepoint
    end

substitute_at(column, index) click to toggle source

Returns a bind substitution value given a `column` and list of current `binds`

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 160
    def substitute_at(column, index)
      Arel::Nodes::BindParam.new '?'
    end

supports_bulk_alter?() click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 122
    def supports_bulk_alter?
      false
    end

supports_count_distinct?() click to toggle source

Does this adapter support using DISTINCT within COUNT? This is `true` for all adapters except sqlite.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 111
    def supports_count_distinct?
      true
    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? PostgreSQL, SQL Server, and others support this. MySQL and others do not.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 118
    def supports_ddl_transactions?
      false
    end

supports_explain?() click to toggle source

Does this adapter support explain? As of this writing sqlite3, mysql2, and postgresql are the only ones that do.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 147
    def supports_explain?
      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 141
    def supports_index_sort_order?
      false
    end

supports_migrations?() click to toggle source

Does this adapter support migrations? Backend specific, as the abstract adapter always returns `false`.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 98
    def supports_migrations?
      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? Backend specific, as the abstract adapter always returns `false`.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 105
    def supports_primary_key?
      false
    end

supports_savepoints?() click to toggle source

Does this adapter support savepoints? PostgreSQL and MySQL do, SQLite < 3.6.8 does not.

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 128
    def supports_savepoints?
      false
    end

transaction_joinable=(joinable) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 242
    def transaction_joinable=(joinable)
      @transaction_joinable = joinable
    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 218
    def verify!(*ignored)
      reconnect! unless active?
    end

### Protected Instance Methods

log(sql, name = "SQL", binds = []) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 274
    def log(sql, name = "SQL", binds = [])
      @instrumenter.instrument(
        "sql.active_record",
        :sql           => sql,
        :name          => name,
        :connection_id => object_id,
        :binds         => binds) { yield }
    rescue Exception => e
      message = "#{e.class.name}: #{e.message}: #{sql}"
      @logger.debug message if @logger
      exception = translate_exception(e, message)
      exception.set_backtrace e.backtrace
      raise exception
    end

translate_exception(e, message) click to toggle source

    # File lib/active_record/connection_adapters/abstract_adapter.rb, line 289
    def translate_exception(e, message)
      # override in derived class
      ActiveRecord::StatementInvalid.new(message)
    end

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