Methods
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Instance Public methods
add_transaction_record(record)

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 242
def add_transaction_record(record)
  last_batch = @_current_transaction_records.last
  last_batch << record if last_batch
end
begin_db_transaction()

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 248
def begin_db_transaction()    end
case_sensitive_equality_operator()
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 284
def case_sensitive_equality_operator
  "="
end
commit_db_transaction()

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 251
def commit_db_transaction()   end
default_sequence_name(table, column)
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 257
def default_sequence_name(table, column)
  nil
end
delete(arel, name = nil, binds = [])

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 100
def delete(arel, name = nil, binds = [])
  exec_delete(to_sql(arel, binds), name, binds)
end
empty_insert_statement_value()
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 280
def empty_insert_statement_value
  "VALUES(DEFAULT)"
end
exec_delete(sql, name, binds)

Executes delete sqlstatement in the context of this connection using bindsas the bind substitutes. nameis the logged along with the executed sql statement.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 69
def exec_delete(sql, name, binds)
  exec_query(sql, name, binds)
end
exec_insert(sql, name, binds)

Executes insert sqlstatement in the context of this connection using bindsas the bind substitutes. nameis the logged along with the executed sql statement.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 62
def exec_insert(sql, name, binds)
  exec_query(sql, name, binds)
end
exec_query(sql, name = 'SQL', binds = [])

Executes sqlstatement in the context of this connection using bindsas the bind substitutes. nameis logged along with the executed sqlstatement.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 56
def exec_query(sql, name = 'SQL', binds = [])
end
exec_update(sql, name, binds)

Executes update sqlstatement in the context of this connection using bindsas the bind substitutes. nameis the logged along with the executed sql statement.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 76
def exec_update(sql, name, binds)
  exec_query(sql, name, binds)
end
execute(sql, name = nil)

Executes the SQL statement in the context of this connection.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 49
def execute(sql, name = nil)
end
insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [])

Returns the last auto-generated ID from the affected table.

id_valuewill 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.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 88
def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = [])
  sql, binds = sql_for_insert(to_sql(arel, binds), pk, id_value, sequence_name, binds)
  value      = exec_insert(sql, name, binds)
  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 (eg. Oracle).

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 268
def insert_fixture(fixture, table_name)
  columns = schema_cache.columns_hash(table_name)

  key_list   = []
  value_list = fixture.map do |name, value|
    key_list << quote_column_name(name)
    quote(value, columns[name])
  end

  execute "INSERT INTO #{quote_table_name(table_name)} (#{key_list.join(', ')}) VALUES (#{value_list.join(', ')})", 'Fixture Insert'
end
limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 288
def limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)
  "WHERE #{quoted_primary_key} IN (SELECT #{quoted_primary_key} FROM #{quoted_table_name} #{where_sql})"
end
outside_transaction?()

Checks whether there is currently no transaction active. This is done by querying the database driver, and does not use the transaction house-keeping information recorded by increment_open_transactions and friends.

Returns true if there is no transaction active, false if there is a transaction active, and nil if this information is unknown.

Not all adapters supports transaction state introspection. Currently, only the PostgreSQL adapter supports this.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 114
def outside_transaction?
  nil
end
reset_sequence!(table, column, sequence = nil)

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 262
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.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 255
def rollback_db_transaction() end
sanitize_limit(limit)

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

The limitmay be anything that can evaluate to a string via to_s. It should look like an integer, or a comma-delimited list of integers, or an Arel SQL literal.

Returns Integer and Arel::Nodes::SqlLiteral limits as is. Returns the sanitized limit parameter, either as an integer, or as a string which contains a comma-delimited list of integers.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 301
def sanitize_limit(limit)
  if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral)
    limit
  elsif limit.to_s =~ /,/
    Arel.sql limit.to_s.split(',').map{ |i| Integer(i) }.join(',')
  else
    Integer(limit)
  end
end
select_all(arel, name = nil, binds = [])

Returns an array of record hashes with the column names as keys and column values as values.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 17
def select_all(arel, name = nil, binds = [])
  select(to_sql(arel, binds), name, binds)
end
select_one(arel, name = nil)

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 23
def select_one(arel, name = nil)
  result = select_all(arel, name)
  result.first if result
end
select_rows(sql, name = nil)

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 44
def select_rows(sql, name = nil)
end
select_value(arel, name = nil)

Returns a single value from a record

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 29
def select_value(arel, name = nil)
  if result = select_one(arel, name)
    result.values.first
  end
end
select_values(arel, name = nil)

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

select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 37
def select_values(arel, name = nil)
  result = select_rows(to_sql(arel, []), name)
  result.map { |v| v[0] }
end
supports_statement_cache?()

Returns truewhen the connection adapter supports prepared statement caching, otherwise returns false

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 120
def supports_statement_cache?
  false
end
to_sql(arel, binds = [])

Converts an arel AST to SQL

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 5
def to_sql(arel, binds = [])
  if arel.respond_to?(:ast)
    visitor.accept(arel.ast) do
      quote(*binds.shift.reverse)
    end
  else
    arel
  end
end
transaction(options = {})

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

Nested transactions support

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/5.0/en/savepoint.html Savepoints are supported by MySQL and PostgreSQL, but not SQLite3.

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_newis set, the block will be wrapped in a database savepoint acting as a sub-transaction.

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
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 166
def transaction(options = {})
  options.assert_valid_keys :requires_new, :joinable

  last_transaction_joinable = defined?(@transaction_joinable) ? @transaction_joinable : nil
  if options.has_key?(:joinable)
    @transaction_joinable = options[:joinable]
  else
    @transaction_joinable = true
  end
  requires_new = options[:requires_new] || !last_transaction_joinable

  transaction_open = false
  @_current_transaction_records ||= []

  begin
    if block_given?
      if requires_new || open_transactions == 0
        if open_transactions == 0
          begin_db_transaction
        elsif requires_new
          create_savepoint
        end
        increment_open_transactions
        transaction_open = true
        @_current_transaction_records.push([])
      end
      yield
    end
  rescue Exception => database_transaction_rollback
    if transaction_open && !outside_transaction?
      transaction_open = false
      decrement_open_transactions
      if open_transactions == 0
        rollback_db_transaction
        rollback_transaction_records(true)
      else
        rollback_to_savepoint
        rollback_transaction_records(false)
      end
    end
    raise unless database_transaction_rollback.is_a?(ActiveRecord::Rollback)
  end
ensure
  @transaction_joinable = last_transaction_joinable

  if outside_transaction?
    @open_transactions = 0
  elsif transaction_open
    decrement_open_transactions
    begin
      if open_transactions == 0
        commit_db_transaction
        commit_transaction_records
      else
        release_savepoint
        save_point_records = @_current_transaction_records.pop
        unless save_point_records.blank?
          @_current_transaction_records.push([]) if @_current_transaction_records.empty?
          @_current_transaction_records.last.concat(save_point_records)
        end
      end
    rescue Exception => database_transaction_rollback
      if open_transactions == 0
        rollback_db_transaction
        rollback_transaction_records(true)
      else
        rollback_to_savepoint
        rollback_transaction_records(false)
      end
      raise
    end
  end
end
update(arel, name = nil, binds = [])

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 95
def update(arel, name = nil, binds = [])
  exec_update(to_sql(arel, binds), name, binds)
end
Instance Protected methods
commit_transaction_records()

Send a commit message to all records after they have been committed.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 366
def commit_transaction_records
  records = @_current_transaction_records.flatten
  @_current_transaction_records.clear
  unless records.blank?
    records.uniq.each do |record|
      begin
        record.committed!
      rescue Exception => e
        record.logger.error(e) if record.respond_to?(:logger) && record.logger
      end
    end
  end
end
delete_sql(sql, name = nil)

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 340
def delete_sql(sql, name = nil)
  update_sql(sql, name)
end
insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)

Returns the last auto-generated ID from the affected table.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 329
def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
  execute(sql, name)
  id_value
end
last_inserted_id(result)
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 384
def last_inserted_id(result)
  row = result.rows.first
  row && row.first
end
rollback_transaction_records(rollback)

Send a rollback message to all records after they have been rolled back. If rollback is false, only rollback records since the last save point.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 346
def rollback_transaction_records(rollback)
  if rollback
    records = @_current_transaction_records.flatten
    @_current_transaction_records.clear
  else
    records = @_current_transaction_records.pop
  end

  unless records.blank?
    records.uniq.each do |record|
      begin
        record.rolledback!(rollback)
      rescue Exception => e
        record.logger.error(e) if record.respond_to?(:logger) && record.logger
      end
    end
  end
end
select(sql, name = nil, binds = [])

Returns an array of record hashes with the column names as keys and column values as values.

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 324
def select(sql, name = nil, binds = [])
end
sql_for_insert(sql, pk, id_value, sequence_name, binds)
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 380
def sql_for_insert(sql, pk, id_value, sequence_name, binds)
  [sql, binds]
end
update_sql(sql, name = nil)

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

# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 335
def update_sql(sql, name = nil)
  execute(sql, name)
end