Module: ActiveRecord::ConnectionAdapters::DatabaseStatements

Included in:
AbstractAdapter
Defined in:
lib/active_record/connection_adapters/abstract/database_statements.rb

Instance Method Summary collapse

Instance Method Details

#add_limit_offset!(sql, options) ⇒ Object

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



217
218
219
220
221
222
223
224
225
 
# File '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) ⇒ Object

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



189
190
191
192
 
# File '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 ⇒ Object

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



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

def begin_db_transaction()    end

#case_sensitive_equality_operator ⇒ Object 



246
247
248
 
# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 246

def case_sensitive_equality_operator
  "="
end

#commit_db_transaction ⇒ Object

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



198
 
# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 198

def commit_db_transaction()   end

#default_sequence_name(table, column) ⇒ Object 



227
228
229
 
# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 227

def default_sequence_name(table, column)
  nil
end

#delete(sql, name = nil) ⇒ Object

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



53
54
55
 
# File '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 ⇒ Object 



242
243
244
 
# File '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) ⇒ Object

Executes the SQL statement in the context of this connection.



38
39
 
# File '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) ⇒ Object

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



43
44
45
 
# File '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) ⇒ Object

Inserts the given fixture into the table. Overridden in adapters that require something beyond a simple insert (eg. Oracle).



238
239
240
 
# File '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) ⇒ Object 



250
251
252
 
# File '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? ⇒ Boolean

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.

Returns:

  • (Boolean) 


67
68
69
 
# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 67

def outside_transaction?
  nil
end

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

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



232
233
234
 
# File '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 ⇒ Object

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



202
 
# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 202

def rollback_db_transaction() end

#sanitize_limit(limit) ⇒ Object

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.



263
264
265
266
267
268
269
270
271
 
# File '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) ⇒ Object

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



6
7
8
 
# File '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) ⇒ Object

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



12
13
14
15
 
# File '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) ⇒ Object

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



33
34
 
# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 33

def select_rows(sql, name = nil)
end

#select_value(sql, name = nil) ⇒ Object

Returns a single value from a record



18
19
20
21
22
 
# File '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) ⇒ Object

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

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



26
27
28
29
 
# File '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 = {}) ⇒ Object

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



113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
 
# File '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) ⇒ Object

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



48
49
50
 
# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 48

def update(sql, name = nil)
  update_sql(sql, name)
end