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Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
Begins the transaction (and turns off auto-committing).
Begins the transaction with the isolation level set. Raises an error by default; adapters that support setting the isolation level should implement this method.
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 421 def build_fixture_sql(fixtures, table_name) columns = schema_cache.columns_hash(table_name) values = fixtures.map do |fixture| fixture = fixture.stringify_keys unknown_columns = fixture.keys - columns.keys if unknown_columns.any? raise Fixture::FixtureError, %(table "#{table_name}" has no columns named #{unknown_columns.map(&:inspect).join(', ')}.) end columns.map do |name, column| if fixture.key?(name) type = lookup_cast_type_from_column(column) bind = Relation::QueryAttribute.new(name, fixture[name], type) with_yaml_fallback(bind.value_for_database) else default_insert_value(column) end end end table = Arel::Table.new(table_name) manager = Arel::InsertManager.new manager.into(table) columns.each_key { |column| manager.columns << table[column] } manager.values = manager.create_values_list(values) manager.to_sql end
Commits the transaction (and turns on auto-committing).
Executes the delete statement and returns the number of rows affected.
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.
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.
Executes sql
statement in the context of this connection using
binds
as the bind substitutes. name
is logged
along with the executed sql
statement.
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.
Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter. Note: depending on your database connector, the result returned by this method may be manually memory managed. Consider using the #exec_query wrapper instead.
Executes an INSERT query and returns the new record's ID
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
.
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 147 def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = []) sql, binds = to_sql_and_binds(arel, binds) value = exec_insert(sql, name, binds, pk, sequence_name) id_value || last_inserted_id(value) end
Inserts the given fixture into the table. Overridden in adapters that require something beyond a simple insert (eg. Oracle). Most of adapters should implement `insert_fixtures` that leverages bulk SQL insert. We keep this method to provide fallback for databases like sqlite that do not support bulk inserts.
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 330 def insert_fixture(fixture, table_name) fixture = fixture.stringify_keys columns = schema_cache.columns_hash(table_name) binds = fixture.map do |name, value| if column = columns[name] type = lookup_cast_type_from_column(column) Relation::QueryAttribute.new(name, value, type) else raise Fixture::FixtureError, %(table "#{table_name}" has no column named #{name.inspect}.) end end table = Arel::Table.new(table_name) values = binds.map do |bind| value = with_yaml_fallback(bind.value_for_database) [table[bind.name], value] end manager = Arel::InsertManager.new manager.into(table) manager.insert(values) execute manager.to_sql, "Fixture Insert" end
Inserts a set of fixtures 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 358 def insert_fixtures(fixtures, table_name) ActiveSupport::Deprecation.warn(<<-MSG.squish) `insert_fixtures` is deprecated and will be removed in the next version of Rails. Consider using `insert_fixtures_set` for performance improvement. MSG return if fixtures.empty? execute(build_fixture_sql(fixtures, table_name), "Fixtures Insert") end def insert_fixtures_set(fixture_set, tables_to_delete = []) fixture_inserts = fixture_set.map do |table_name, fixtures| next if fixtures.empty? build_fixture_sql(fixtures, table_name) end.compact table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name table}".dup } total_sql = Array.wrap(combine_multi_statements(table_deletes + fixture_inserts)) disable_referential_integrity do transaction(requires_new: true) do total_sql.each do |sql| execute sql, "Fixtures Load" yield if block_given? end end end end def empty_insert_statement_value "DEFAULT VALUES" 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 an Arel SQL literal. # # Returns Integer and Arel::Nodes::SqlLiteral limits as is. def sanitize_limit(limit) if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral) limit 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, key) # :nodoc: subselect = subquery_for(key, select) update.where key.in(subselect) end alias join_to_delete join_to_update private def default_insert_value(column) Arel.sql("DEFAULT") end def build_fixture_sql(fixtures, table_name) columns = schema_cache.columns_hash(table_name) values = fixtures.map do |fixture| fixture = fixture.stringify_keys unknown_columns = fixture.keys - columns.keys if unknown_columns.any? raise Fixture::FixtureError, %(table "#{table_name}" has no columns named #{unknown_columns.map(&:inspect).join(', ')}.) end columns.map do |name, column| if fixture.key?(name) type = lookup_cast_type_from_column(column) bind = Relation::QueryAttribute.new(name, fixture[name], type) with_yaml_fallback(bind.value_for_database) else default_insert_value(column) end end end table = Arel::Table.new(table_name) manager = Arel::InsertManager.new manager.into(table) columns.each_key { |column| manager.columns << table[column] } manager.values = manager.create_values_list(values) manager.to_sql end def combine_multi_statements(total_sql) total_sql.join(";\n") end # 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 = []) exec_query(sql, name, binds, prepare: false) end def select_prepared(sql, name = nil, binds = []) exec_query(sql, name, binds, prepare: true) end def sql_for_insert(sql, pk, id_value, sequence_name, binds) [sql, binds] end def last_inserted_id(result) single_value_from_rows(result.rows) end def single_value_from_rows(rows) row = rows.first row && row.first end def arel_from_relation(relation) if relation.is_a?(Relation) relation.arel else relation end end # Fixture value is quoted by Arel, however scalar values # are not quotable. In this case we want to convert # the column value to YAML. def with_yaml_fallback(value) if value.is_a?(Hash) || value.is_a?(Array) YAML.dump(value) else value end end class PartialQueryCollector def initialize @parts = [] @binds = [] end def <<(str) @parts << str self end def add_bind(obj) @binds << obj @parts << Arel::Nodes::BindParam.new(1) self end def value [@parts, @binds] end end end
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 368 def insert_fixtures_set(fixture_set, tables_to_delete = []) fixture_inserts = fixture_set.map do |table_name, fixtures| next if fixtures.empty? build_fixture_sql(fixtures, table_name) end.compact table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name table}".dup } total_sql = Array.wrap(combine_multi_statements(table_deletes + fixture_inserts)) disable_referential_integrity do transaction(requires_new: true) do total_sql.each do |sql| execute sql, "Fixtures Load" yield if block_given? end end end end
Set the sequence to the max value of the table's column.
Rolls back the transaction (and turns on auto-committing). Must be done if the transaction block raises an exception or returns false.
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 an Arel SQL literal.
Returns Integer and Arel::Nodes::SqlLiteral limits as is.
Returns an ActiveRecord::Result instance.
Returns an ActiveRecord::Result instance.
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 46 def select_all(arel, name = nil, binds = [], preparable: nil) arel = arel_from_relation(arel) sql, binds = to_sql_and_binds(arel, binds) if !prepared_statements || (arel.is_a?(String) && preparable.nil?) preparable = false else preparable = visitor.preparable end if prepared_statements && preparable select_prepared(sql, name, binds) else select(sql, name, binds) end end
Returns a record hash with the column names as keys and column values as values.
Returns an array of arrays containing the field values. Order is the same
as that returned by columns
.
Returns a single value from a record
Returns an array of the values of the first column in a select:
select_values("SELECT id FROM companies LIMIT 3") => [1,2,3]
Returns a subquery for the given key using the join information.
Converts an arel AST to SQL
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/5.7/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:
-
:read_uncommitted
-
:read_committed
-
:repeatable_read
-
:serializable
You should consult the documentation for your database to understand the semantics of these different levels:
An ActiveRecord::TransactionIsolationError 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 mysql2 and postgresql adapters support setting the transaction isolation level.
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 247 def transaction(requires_new: nil, isolation: nil, joinable: true) if !requires_new && current_transaction.joinable? if isolation raise ActiveRecord::TransactionIsolationError, "cannot set isolation when joining a transaction" end yield else transaction_manager.within_new_transaction(isolation: isolation, joinable: joinable) { yield } end rescue ActiveRecord::Rollback # rollbacks are silently swallowed end
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 285 def transaction_isolation_levels { read_uncommitted: "READ UNCOMMITTED", read_committed: "READ COMMITTED", repeatable_read: "REPEATABLE READ", serializable: "SERIALIZABLE" } end
Executes the truncate statement.
Executes the update statement and returns the number of rows affected.
Fixture value is quoted by Arel, however scalar values are not quotable. In this case we want to convert the column value to YAML.