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Module: ActiveRecord::ConnectionAdapters::DatabaseStatements

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Included In:
AbstractAdapter, AbstractMysqlAdapter, Mysql2Adapter, PostgreSQLAdapter, SQLite3Adapter
Defined in: activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb

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 328



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


  








  

    #commit_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 328



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


  








  

    #current_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 328



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


  








  

    #materialize_transactions   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 328



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


  








  

    #open_transactions   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 328



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


  








  

    #rollback_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 328



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


  








  

    #transaction_open?  ⇒ Boolean  (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 339



def transaction_open?
  current_transaction.open?
end


  








  

    #within_new_transaction   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 328



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, 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 349



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 354



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 368



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 373



def commit_db_transaction()   end


  








  

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



  

    

Alias for #insert.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 174



alias create insert


  








  

    #default_sequence_name(table, column)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 387



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 183



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 328



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


  








  

    #empty_insert_statement_value(primary_key = nil)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 419



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 328



delegate :within_new_transaction, :open_transactions, :current_transaction, :begin_transaction,
         :commit_transaction, :rollback_transaction, :materialize_transactions,
         :disable_lazy_transactions!, :enable_lazy_transactions!, 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 142



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


  








  

    #exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = 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.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 134



def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil)
  sql, binds = sql_for_insert(sql, pk, binds)
  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.


  





  
Raises:


    
  
  • 
    (NotImplementedError)
  
    • 





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 127



def exec_query(sql, name = "SQL", binds = [], prepare: false)
  raise NotImplementedError
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 149



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


  








  

    #execute(sql, name = nil)  
  



  

    

Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter. Note: depending on your database connector, the result returned by this method may be manually memory managed. Consider using the exec_query wrapper instead.


  





  
Raises:


    
  
  • 
    (NotImplementedError)
  
    • 





  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 120



def execute(sql, name = nil)
  raise NotImplementedError
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 = [])  
    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.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 169



def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [])
  sql, binds = to_sql_and_binds(arel, binds)
  value = exec_insert(sql, name, binds, pk, sequence_name)
  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 401



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 405



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
    disable_referential_integrity do
      transaction(requires_new: true) 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 392



def reset_sequence!(table, column, sequence = nil)
  # Do nothing by default. Implement for PostgreSQL, Oracle, ...
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 377



def rollback_db_transaction
  exec_rollback_db_transaction
end


  








  

    #rollback_to_savepoint(name = nil)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 383



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 429



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)  
  



  

    

Returns an ::ActiveRecord::Result instance.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 62



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

  if prepared_statements && preparable
    select_prepared(sql, name, binds)
  else
    select(sql, name, binds)
  end
rescue ::RangeError
  ActiveRecord::Result.new([], [])
end


  








  

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



  

    

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 77



def select_one(arel, name = nil, binds = [])
  select_all(arel, name, binds).first
end


  








  

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



  

    

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 94



def select_rows(arel, name = nil, binds = [])
  select_all(arel, name, binds).rows
end


  








  

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



  

    

Returns a single value from a record


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 82



def select_value(arel, name = nil, binds = [])
  single_value_from_rows(select_rows(arel, name, binds))
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 88



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)  
  



  

    

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



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.connection.transaction do  # BEGIN
  Model.connection.transaction(requires_new: true) do  # CREATE SAVEPOINT active_record_1
    Model.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 and postgresql adapters support setting the transaction isolation level.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb', line 313



def transaction(requires_new: nil, isolation: nil, joinable: true)
  if !requires_new && current_transaction.joinable?
    if isolation
      raise ActiveRecord::TransactionIsolationError, "cannot set isolation when joining a transaction"
    end
    yield
  else
    transaction_manager.within_new_transaction(isolation: isolation, joinable: joinable) { yield }
  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 356



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 189



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 177



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 111



def write_query?(sql)
  raise NotImplementedError
end