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module ActiveRecord
module ConnectionAdapters # :nodoc:
module DatabaseStatements
def initialize
super
reset_transaction
end
# Converts an arel AST to SQL
def to_sql(arel, binds = [])
if arel.respond_to?(:ast)
binds = binds.dup
visitor.accept(arel.ast) do
quote(*binds.shift.reverse)
end
else
arel
end
end
# Returns an ActiveRecord::Result instance.
def select_all(arel, name = nil, binds = [])
select(to_sql(arel, binds), name, binds)
end
# Returns a record hash with the column names as keys and column values
# as values.
def select_one(arel, name = nil, binds = [])
select_all(arel, name, binds).first
end
# Returns a single value from a record
def select_value(arel, name = nil, binds = [])
if result = select_one(arel, name, binds)
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(arel, name = nil)
select_rows(to_sql(arel, []), name)
.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)
end
undef_method :execute
# Executes +sql+ statement in the context of this connection using
# +binds+ as the bind substitutes. +name+ is logged along with
# the executed +sql+ statement.
def exec_query(sql, name = 'SQL', binds = [])
end
# 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.
def exec_insert(sql, name, binds, pk = nil, sequence_name = nil)
exec_query(sql, name, binds)
end
# 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.
def exec_delete(sql, name, binds)
exec_query(sql, name, binds)
end
# 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.
def exec_update(sql, name, binds)
exec_query(sql, name, binds)
end
# Returns the last auto-generated ID from the affected table.
#
# +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+.
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, pk, sequence_name)
id_value || last_inserted_id(value)
end
# Executes the update statement and returns the number of rows affected.
def update(arel, name = nil, binds = [])
exec_update(to_sql(arel, binds), name, binds)
end
# Executes the delete statement and returns the number of rows affected.
def delete(arel, name = nil, binds = [])
exec_delete(to_sql(arel, binds), name, binds)
end
# Returns +true+ when the connection adapter supports prepared statement
# caching, otherwise returns +false+
def supports_statement_cache?
false
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/savepoint.html
# Savepoints are supported by MySQL and PostgreSQL. SQLite3 version >= '3.6.8'
# supports savepoints.
#
# 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
#
# == 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:
#
# * <tt>:read_uncommitted</tt>
# * <tt>:read_committed</tt>
# * <tt>:repeatable_read</tt>
# * <tt>:serializable</tt>
#
# You should consult the documentation for your database to understand the
# semantics of these different levels:
#
# * http://www.postgresql.org/docs/9.1/static/transaction-iso.html
# * https://dev.mysql.com/doc/refman/5.0/en/set-transaction.html
#
# An <tt>ActiveRecord::TransactionIsolationError</tt> 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 mysql, mysql2 and postgresql adapters support setting the transaction
# isolation level. However, support is disabled for mysql versions below 5,
# because they are affected by a bug[http://bugs.mysql.com/bug.php?id=39170]
# which means the isolation level gets persisted outside the transaction.
def transaction(options = {})
options.assert_valid_keys :requires_new, :joinable, :isolation
if !options[:requires_new] && current_transaction.joinable?
if options[:isolation]
raise ActiveRecord::TransactionIsolationError, "cannot set isolation when joining a transaction"
end
yield
else
within_new_transaction(options) { yield }
end
rescue ActiveRecord::Rollback
# rollbacks are silently swallowed
end
def within_new_transaction(options = {}) #:nodoc:
transaction = begin_transaction(options)
yield
rescue Exception => error
rollback_transaction if transaction
raise
ensure
begin
commit_transaction unless error
rescue Exception
rollback_transaction
raise
end
end
def current_transaction #:nodoc:
@transaction
end
def transaction_open?
@transaction.open?
end
def begin_transaction(options = {}) #:nodoc:
@transaction = @transaction.begin(options)
end
def commit_transaction #:nodoc:
@transaction = @transaction.commit
end
def rollback_transaction #:nodoc:
@transaction = @transaction.rollback
end
def reset_transaction #:nodoc:
@transaction = ClosedTransaction.new(self)
end
# Register a record with the current transaction so that its after_commit and after_rollback callbacks
# can be called.
def add_transaction_record(record)
@transaction.add_record(record)
end
# Begins the transaction (and turns off auto-committing).
def begin_db_transaction() end
def transaction_isolation_levels
{
read_uncommitted: "READ UNCOMMITTED",
read_committed: "READ COMMITTED",
repeatable_read: "REPEATABLE READ",
serializable: "SERIALIZABLE"
}
end
# Begins the transaction with the isolation level set. Raises an error by
# default; adapters that support setting the isolation level should implement
# this method.
def begin_isolated_db_transaction(isolation)
raise ActiveRecord::TransactionIsolationError, "adapter does not support setting transaction isolation"
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
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 fixture_sql(fixture, table_name), 'Fixture Insert'
end
def fixture_sql(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
"INSERT INTO #{quote_table_name(table_name)} (#{key_list.join(', ')}) VALUES (#{value_list.join(', ')})"
end
def empty_insert_statement_value
"DEFAULT VALUES"
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
# 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.
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
# The default strategy for an UPDATE with joins is to use a subquery. This doesn't work
# on mysql (even when aliasing the tables), but mysql allows using JOIN directly in
# an UPDATE statement, so in the mysql adapters we redefine this to do that.
def join_to_update(update, select) #:nodoc:
key = update.key
subselect = subquery_for(key, select)
update.where key.in(subselect)
end
def join_to_delete(delete, select, key) #:nodoc:
subselect = subquery_for(key, select)
delete.where key.in(subselect)
end
protected
# Returns a subquery for the given key using the join information.
def subquery_for(key, select)
subselect = select.clone
subselect.projections = [key]
subselect
end
# Returns an ActiveRecord::Result instance.
def select(sql, name = nil, binds = [])
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
def sql_for_insert(sql, pk, id_value, sequence_name, binds)
[sql, binds]
end
def last_inserted_id(result)
row = result.rows.first
row && row.first
end
end
end
end
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