Module: ActiveRecord::ConnectionAdapters::DatabaseStatements

add_limit_offset!(sql, options)

Appends LIMIT and OFFSET options to an SQL statement, or some SQL fragment that has the same semantics as LIMIT and OFFSET.

options must be a Hash which contains a :limit option and an :offset option.

This method modifies the sql parameter.

Examples

add_limit_offset!('SELECT * FROM suppliers', {:limit => 10, :offset => 50})

generates

SELECT * FROM suppliers LIMIT 10 OFFSET 50

[ show source ]

  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 217
def add_limit_offset!(sql, options)
  if limit = options[:limit]
    sql << " LIMIT #{sanitize_limit(limit)}"
  end
  if offset = options[:offset]
    sql << " OFFSET #{offset.to_i}"
  end
  sql
end

add_transaction_record(record)

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 189
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).

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 195
def begin_db_transaction()    end

case_sensitive_equality_operator()

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 246
def case_sensitive_equality_operator
  "="
end

commit_db_transaction()

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 198
def commit_db_transaction()   end

default_sequence_name(table, column)

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 227
def default_sequence_name(table, column)
  nil
end

delete(sql, name = nil)

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

[ show source ]

  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 53
def delete(sql, name = nil)
  delete_sql(sql, name)
end

empty_insert_statement_value()

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 242
def empty_insert_statement_value
  "VALUES(DEFAULT)"
end

execute(sql, name = nil, skip_logging = false)

Executes the SQL statement in the context of this connection.

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 38
def execute(sql, name = nil, skip_logging = false)
end

insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 43
def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
  insert_sql(sql, name, pk, id_value, sequence_name)
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).

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 238
def insert_fixture(fixture, table_name)
  execute "INSERT INTO #{quote_table_name(table_name)} (#{fixture.key_list}) VALUES (#{fixture.value_list})", 'Fixture Insert'
end

limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key)

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 250
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.

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 67
def outside_transaction?
  nil
end

reset_sequence!(table, column, sequence = nil)

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 232
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.

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 202
def rollback_db_transaction() 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 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.

[ show source ]

  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 263
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(sql, name = nil)

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

[ show source ]

  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 6
def select_all(sql, name = nil)
  select(sql, name)
end

select_one(sql, name = nil)

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 12
def select_one(sql, name = nil)
  result = select_all(sql, 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.

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 33
def select_rows(sql, name = nil)
end

select_value(sql, name = nil)

Returns a single value from a record

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 18
def select_value(sql, name = nil)
  if result = select_one(sql, name)
    result.values.first
  end
end

select_values(sql, 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]

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 26
def select_values(sql, name = nil)
  result = select_rows(sql, name)
  result.map { |v| v[0] }
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/savepoints.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_new is 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

[ show source ]

  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 113
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(sql, name = nil)

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 48
def update(sql, name = nil)
  update_sql(sql, name)
end

commit_transaction_records()

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 318
def commit_transaction_records #:nodoc
  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.

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 292
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.

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 281
def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
  execute(sql, name)
  id_value
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.

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 298
def rollback_transaction_records(rollback) #:nodoc
  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)

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

[ show source ]

  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 276
def select(sql, name = nil)
end

update_sql(sql, name = nil)

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

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  # File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 287
def update_sql(sql, name = nil)
  execute(sql, name)
end