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Module: ActiveRecord::ConnectionAdapters::DatabaseStatements

Constant Summary

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#begin_transaction (readonly)

[ GitHub ] 

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #commit_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #current_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #dirty_current_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #materialize_transactions   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #open_transactions   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #rollback_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #transaction_open?  ⇒ Boolean  (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 381



def transaction_open?
  current_transaction.open?
end


  








  

    #within_new_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  







Instance Method Details



  

    #add_transaction_record(record, ensure_finalize = true)  
  



  

    

Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 407



def add_transaction_record(record, ensure_finalize = true)
  current_transaction.add_record(record, ensure_finalize)
end


  








  

    #begin_db_transaction  
  



  

    

Begins the transaction (and turns off auto-committing).


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 412



def begin_db_transaction()    end


  








  

    #begin_isolated_db_transaction(isolation)  
  



  

    

Begins the transaction with the isolation level set. Raises an error by default; adapters that support setting the isolation level should implement this method.


  





  
Raises:





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 426



def begin_isolated_db_transaction(isolation)
  raise ActiveRecord::TransactionIsolationError, "adapter does not support setting transaction isolation"
end


  








  

    #commit_db_transaction  
  



  

    

Commits the transaction (and turns on auto-committing).


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 431



def commit_db_transaction()   end


  








  

    #create(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)  
  



  

    

Alias for #insert.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 203



alias create insert


  








  

    #default_sequence_name(table, column)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 453



def default_sequence_name(table, column)
  nil
end


  








  

    #delete(arel, name = nil, binds = [])  
  



  

    

Executes the delete statement and returns the number of rows affected.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 212



def delete(arel, name = nil, binds = [])
  sql, binds = to_sql_and_binds(arel, binds)
  exec_delete(sql, name, binds)
end


  








  

    #disable_lazy_transactions!  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #empty_insert_statement_value(primary_key = nil)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 485



def empty_insert_statement_value(primary_key = nil)
  "DEFAULT VALUES"
end


  








  

    #enable_lazy_transactions!  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 369



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, :dirty_current_transaction,
         to: :transaction_manager


  








  

    #exec_delete(sql, name = nil, binds = [])  
  



  

    

Executes delete sql statement in the context of this connection using binds as the bind substitutes. name is logged along with the executed sql statement.


  



  [ GitHub ]


  

  


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



def exec_delete(sql, name = nil, binds = [])
  internal_exec_query(sql, name, binds)
end


  








  

    #exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil, returning: nil)  
  



  

    

Executes insert sql statement in the context of this connection using binds as the bind substitutes. name is logged along with the executed sql statement. Some adapters support the returning keyword argument which allows to control the result of the query: nil is the default value and maintains default behavior. If an array of column names is passed - the result will contain values of the specified columns from the inserted row.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 157



def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil, returning: nil)
  sql, binds = sql_for_insert(sql, pk, binds, returning)
  internal_exec_query(sql, name, binds)
end


  








  

    #exec_query(sql, name = "SQL", binds = [], prepare: false)  
  



  

    

Executes sql statement in the context of this connection using binds as the bind substitutes. name is logged along with the executed sql statement.



Note: the query is assumed to have side effects and the query cache will be cleared. If the query is read-only, consider using #select_all instead.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 147



def exec_query(sql, name = "SQL", binds = [], prepare: false)
  internal_exec_query(sql, name, binds, prepare: prepare)
end


  








  

    #exec_update(sql, name = nil, binds = [])  
  



  

    

Executes update sql statement in the context of this connection using binds as the bind substitutes. name is logged along with the executed sql statement.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 172



def exec_update(sql, name = nil, binds = [])
  internal_exec_query(sql, name, binds)
end


  








  

    #execute(sql, name = nil, allow_retry: false)  
  



  

    

Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter.



Setting allow_retry to true causes the db to reconnect and retry executing the SQL statement in case of a connection-related exception. This option should only be enabled for known idempotent queries.



Note: the query is assumed to have side effects and the query cache will be cleared. If the query is read-only, consider using #select_all instead.



Note: depending on your database connector, the result returned by this method may be manually memory managed. Consider using #exec_query wrapper instead.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 136



def execute(sql, name = nil, allow_retry: false)
  internal_execute(sql, name, allow_retry: allow_retry)
end


  








  

    #high_precision_current_timestamp  
  



  

    

Returns an ::Arel SQL literal for the CURRENT_TIMESTAMP for usage with arbitrary precision date/time columns.



Adapters supporting datetime with precision should override this to provide as much precision as is available.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 523



def high_precision_current_timestamp
  HIGH_PRECISION_CURRENT_TIMESTAMP
end


  








  

    #initialize  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 6



def initialize
  super
  reset_transaction
end


  








  

    #insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)  
    Also known as: #create
  



  

    

Executes an INSERT query and returns the new record’s ID



id_value will be returned unless the value is nil, in which case the database will attempt to calculate the last inserted id and return that value.



If the next id was calculated in advance (as in Oracle), it should be passed in as id_value. Some adapters support the returning keyword argument which allows defining the return value of the method: nil is the default value and maintains default behavior. If an array of column names is passed - an array of is returned from the method representing values of the specified columns from the inserted row.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 195



def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [], returning: nil)
  sql, binds = to_sql_and_binds(arel, binds)
  value = exec_insert(sql, name, binds, pk, sequence_name, returning: returning)

  return returning_column_values(value) unless returning.nil?

  id_value || last_inserted_id(value)
end


  








  

    #insert_fixture(fixture, table_name)  
  



  

    

Inserts the given fixture into the table. Overridden in adapters that require something beyond a simple insert (e.g. Oracle). Most of adapters should implement #insert_fixtures_set that leverages bulk SQL insert. We keep this method to provide fallback for databases like SQLite that do not support bulk inserts.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 467



def insert_fixture(fixture, table_name)
  execute(build_fixture_sql(Array.wrap(fixture), table_name), "Fixture Insert")
end


  








  

    #insert_fixtures_set(fixture_set, tables_to_delete = [])  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 471



def insert_fixtures_set(fixture_set, tables_to_delete = [])
  fixture_inserts = build_fixture_statements(fixture_set)
  table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name(table)}" }
  statements = table_deletes + fixture_inserts

  with_multi_statements do
    transaction(requires_new: true) do
      disable_referential_integrity do
        execute_batch(statements, "Fixtures Load")
      end
    end
  end
end


  








  

    #reset_sequence!(table, column, sequence = nil)  
  



  

    

Set the sequence to the max value of the table’s column.


  



  [ GitHub ]


  

  


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



def reset_sequence!(table, column, sequence = nil)
  # Do nothing by default. Implement for PostgreSQL, Oracle, ...
end


  








  

    #restart_db_transaction  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 443



def restart_db_transaction
  exec_restart_db_transaction
end


  








  

    #rollback_db_transaction  
  



  

    

Rolls back the transaction (and turns on auto-committing). Must be done if the transaction block raises an exception or returns false.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 435



def rollback_db_transaction
  exec_rollback_db_transaction
rescue ActiveRecord::ConnectionNotEstablished, ActiveRecord::ConnectionFailed
  # Connection's gone; that counts as a rollback
end


  








  

    #rollback_to_savepoint(name = nil)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 449



def rollback_to_savepoint(name = nil)
  exec_rollback_to_savepoint(name)
end


  








  

    #sanitize_limit(limit)  
  



  

    

Sanitizes the given LIMIT parameter in order to prevent SQL injection.



The limit may be anything that can evaluate to a string via #to_s. It should look like an integer, or an ::Arel SQL literal.



Returns Integer and ::Arel::Nodes::SqlLiteral limits as is.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 495



def sanitize_limit(limit)
  if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral)
    limit
  else
    Integer(limit)
  end
end


  








  

    #select_all(arel, name = nil, binds = [], preparable: nil, async: false, allow_retry: false)  
  



  

    

Returns an ::ActiveRecord::Result instance.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 69



def select_all(arel, name = nil, binds = [], preparable: nil, async: false, allow_retry: false)
  arel = arel_from_relation(arel)
  sql, binds, preparable, allow_retry = to_sql_and_binds(arel, binds, preparable, allow_retry)

  select(sql, name, binds,
    prepare: prepared_statements && preparable,
    async: async && FutureResult::SelectAll,
    allow_retry: allow_retry
  )
rescue ::RangeError
  ActiveRecord::Result.empty(async: async)
end


  








  

    #select_one(arel, name = nil, binds = [], async: false)  
  



  

    

Returns a record hash with the column names as keys and column values as values.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 84



def select_one(arel, name = nil, binds = [], async: false)
  select_all(arel, name, binds, async: async).then(&:first)
end


  








  

    #select_rows(arel, name = nil, binds = [], async: false)  
  



  

    

Returns an array of arrays containing the field values. Order is the same as that returned by columns.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 101



def select_rows(arel, name = nil, binds = [], async: false)
  select_all(arel, name, binds, async: async).then(&:rows)
end


  








  

    #select_value(arel, name = nil, binds = [], async: false)  
  



  

    

Returns a single value from a record


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 89



def select_value(arel, name = nil, binds = [], async: false)
  select_rows(arel, name, binds, async: async).then { |rows| single_value_from_rows(rows) }
end


  








  

    #select_values(arel, name = nil, binds = [])  
  



  

    

Returns an array of the values of the first column in a select:



select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 95



def select_values(arel, name = nil, binds = [])
  select_rows(arel, name, binds).map(&:first)
end


  








  

    #to_sql(arel_or_sql_string, binds = [])  
  



  

    

Converts an arel AST to SQL


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 12



def to_sql(arel_or_sql_string, binds = [])
  sql, _ = to_sql_and_binds(arel_or_sql_string, binds)
  sql
end


  








  

    #transaction(requires_new: nil, isolation: nil, joinable: true, &block)  
  



  

    

Runs the given block in a database transaction, and returns the result of the block.



Transaction callbacks



#transaction yields an ::ActiveRecord::Transaction object on which it is possible to register callback:



ActiveRecord::Base.transaction do |transaction|
  transaction.before_commit { puts "before commit!" }
  transaction.after_commit { puts "after commit!" }
  transaction.after_rollback { puts "after rollback!" }
end



Nested transactions support



#transaction calls can be nested. By default, this makes all database statements in the nested transaction block become part of the parent transaction. For example, the following behavior may be surprising:



ActiveRecord::Base.transaction do
  Post.create(title: 'first')
  ActiveRecord::Base.transaction do
    Post.create(title: 'second')
    raise ActiveRecord::Rollback
  end
end



This creates both “first” and “second” posts. Reason is the ::ActiveRecord::Rollback exception in the nested block does not issue a ROLLBACK. Since these exceptions are captured in transaction blocks, the parent block does not see it and the real transaction is committed.



Most databases don’t support true nested transactions. At the time of writing, the only database that supports true nested transactions that we’re aware of, is MS-SQL.



In order to get around this problem, #transaction will emulate the effect of nested transactions, by using savepoints: dev.mysql.com/doc/refman/en/savepoint.html.



It is safe to call this method if a database transaction is already open, i.e. if #transaction is called within another #transaction block. In case of a nested call, #transaction will behave as follows:


  • 

    The block will be run without doing anything. All database statements that happen within the block are effectively appended to the already open database transaction.
    

  • 

    However, if :requires_new is set, the block will be wrapped in a database savepoint acting as a sub-transaction.
    




In order to get a ROLLBACK for the nested transaction you may ask for a real sub-transaction by passing requires_new: true. If anything goes wrong, the database rolls back to the beginning of the sub-transaction without rolling back the parent transaction. If we add it to the previous example:



ActiveRecord::Base.transaction do
  Post.create(title: 'first')
  ActiveRecord::Base.transaction(requires_new: true) do
    Post.create(title: 'second')
    raise ActiveRecord::Rollback
  end
end



only post with title “first” is created.



See ::ActiveRecord::Transactions to learn more.



Caveats



MySQL doesn’t support DDL transactions. If you perform a DDL operation, then any created savepoints will be automatically released. For example, if you’ve created a savepoint, then you execute a CREATE TABLE statement, then the savepoint that was created will be automatically released.



This means that, on MySQL, you shouldn’t execute DDL operations inside a #transaction call that you know might create a savepoint. Otherwise, #transaction will raise exceptions when it tries to release the already-automatically-released savepoints:



Model.lease_connection.transaction do  # BEGIN
  Model.lease_connection.transaction(requires_new: true) do  # CREATE SAVEPOINT active_record_1
    Model.lease_connection.create_table(...)
    # active_record_1 now automatically released
  end  # RELEASE SAVEPOINT active_record_1  <--- BOOM! database error!
end



Transaction isolation



If your database supports setting the isolation level for a transaction, you can set it like so:



Post.transaction(isolation: :serializable) do
  # ...
end



Valid isolation levels are:


  • 

    :read_uncommitted
    

  • 

    :read_committed
    

  • 

    :repeatable_read
    

  • 

    :serializable
    




You should consult the documentation for your database to understand the semantics of these different levels:




An ::ActiveRecord::TransactionIsolationError will be raised if:


  • 

    The adapter does not support setting the isolation level
    

  • 

    You are joining an existing open transaction
    

  • 

    You are creating a nested (savepoint) transaction
    




The mysql2, trilogy, and postgresql adapters support setting the transaction isolation level.



:args: (requires_new: nil, isolation: nil, &block)


  



  [ GitHub ]


  

  


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



def transaction(requires_new: nil, isolation: nil, joinable: true, &block)
  if !requires_new && current_transaction.joinable?
    if isolation
      raise ActiveRecord::TransactionIsolationError, "cannot set isolation when joining a transaction"
    end
    yield current_transaction.user_transaction
  else
    transaction_manager.within_new_transaction(isolation: isolation, joinable: joinable, &block)
  end
rescue ActiveRecord::Rollback
  # rollbacks are silently swallowed
end


  








  

    #transaction_isolation_levels  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 414



def transaction_isolation_levels
  {
    read_uncommitted: "READ UNCOMMITTED",
    read_committed:   "READ COMMITTED",
    repeatable_read:  "REPEATABLE READ",
    serializable:     "SERIALIZABLE"
  }
end


  








  

    #truncate(table_name, name = nil)  
  



  

    

Executes the truncate statement.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 218



def truncate(table_name, name = nil)
  execute(build_truncate_statement(table_name), name)
end


  








  

    #update(arel, name = nil, binds = [])  
  



  

    

Executes the update statement and returns the number of rows affected.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 206



def update(arel, name = nil, binds = [])
  sql, binds = to_sql_and_binds(arel, binds)
  exec_update(sql, name, binds)
end


  








  

    #write_query?(sql)  ⇒ Boolean 
  



  

    

Determines whether the SQL statement is a write query.


  





  
Raises:


    
  
  • 
    (NotImplementedError)
  
    • 





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 118



def write_query?(sql)
  raise NotImplementedError
end