module ActiveRecord
module ConnectionAdapters # :nodoc:
module DatabaseStatements
# Returns an array of record hashes with the column names as keys and
# column values as values.
def select_all(sql, name = nil)
select(sql, name)
end
# Returns a record hash with the column names as keys and column values
# as values.
def select_one(sql, name = nil)
result = select_all(sql, name)
result.first if result
end
# Returns a single value from a record
def select_value(sql, name = nil)
if result = select_one(sql, name)
result.values.first
end
end
# Returns an array of the values of the first column in a select:
# select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]
def select_values(sql, name = nil)
result = select_rows(sql, name)
result.map { |v| v[0] }
end
# Returns an array of arrays containing the field values.
# Order is the same as that returned by +columns+.
def select_rows(sql, name = nil)
end
undef_method :select_rows
# Executes the SQL statement in the context of this connection.
def execute(sql, name = nil, skip_logging = false)
end
undef_method :execute
# Returns the last auto-generated ID from the affected table.
def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
insert_sql(sql, name, pk, id_value, sequence_name)
end
# Executes the update statement and returns the number of rows affected.
def update(sql, name = nil)
update_sql(sql, name)
end
# Executes the delete statement and returns the number of rows affected.
def delete(sql, name = nil)
delete_sql(sql, name)
end
# 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.
def outside_transaction?
nil
end
# 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:
# http://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
def transaction(options = {})
options.assert_valid_keys :requires_new, :joinable
last_transaction_joinable = @transaction_joinable
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
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
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
else
rollback_to_savepoint
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
else
release_savepoint
end
rescue Exception => database_transaction_rollback
if open_transactions == 0
rollback_db_transaction
else
rollback_to_savepoint
end
raise
end
end
end
# Begins the transaction (and turns off auto-committing).
def begin_db_transaction() end
# Commits the transaction (and turns on auto-committing).
def commit_db_transaction() end
# Rolls back the transaction (and turns on auto-committing). Must be
# done if the transaction block raises an exception or returns false.
def rollback_db_transaction() end
# Alias for <tt>add_limit_offset!</tt>.
def add_limit!(sql, options)
add_limit_offset!(sql, options) if options
end
# 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 (required)
# and an +:offset+ option (optional).
#
# 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
def add_limit_offset!(sql, options)
if limit = options[:limit]
sql << " LIMIT #{sanitize_limit(limit)}"
if offset = options[:offset]
sql << " OFFSET #{offset.to_i}"
end
end
sql
end
# Appends a locking clause to an SQL statement.
# This method *modifies* the +sql+ parameter.
# # SELECT * FROM suppliers FOR UPDATE
# add_lock! 'SELECT * FROM suppliers', :lock => true
# add_lock! 'SELECT * FROM suppliers', :lock => ' FOR UPDATE'
def add_lock!(sql, options)
case lock = options[:lock]
when true; sql << ' FOR UPDATE'
when String; sql << " #{lock}"
end
end
def default_sequence_name(table, column)
nil
end
# Set the sequence to the max value of the table's column.
def reset_sequence!(table, column, sequence = nil)
# Do nothing by default. Implement for PostgreSQL, Oracle, ...
end
# Inserts the given fixture into the table. Overridden in adapters that require
# something beyond a simple insert (eg. Oracle).
def insert_fixture(fixture, table_name)
execute "INSERT INTO #{quote_table_name(table_name)} (#{fixture.key_list}) VALUES (#{fixture.value_list})", 'Fixture Insert'
end
def empty_insert_statement(table_name)
"INSERT INTO #{quote_table_name(table_name)} VALUES(DEFAULT)"
end
def case_sensitive_equality_operator
"="
end
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
protected
# Returns an array of record hashes with the column names as keys and
# column values as values.
def select(sql, name = nil)
end
undef_method :select
# Returns the last auto-generated ID from the affected table.
def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
execute(sql, name)
id_value
end
# Executes the update statement and returns the number of rows affected.
def update_sql(sql, name = nil)
execute(sql, name)
end
# Executes the delete statement and returns the number of rows affected.
def delete_sql(sql, name = nil)
update_sql(sql, name)
end
# Sanitizes the given LIMIT parameter in order to prevent SQL injection.
#
# +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.
#
# Returns the sanitized limit parameter, either as an integer, or as a
# string which contains a comma-delimited list of integers.
def sanitize_limit(limit)
if limit.to_s =~ /,/
limit.to_s.split(',').map{ |i| i.to_i }.join(',')
else
limit.to_i
end
end
end
end
end
