module ActiveRecord::ConnectionAdapters::DatabaseStatements
Constants
- DEFAULT_INSERT_VALUE
Public Class Methods
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 6 def initialize super reset_transaction end
Public Instance Methods
Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 302 def add_transaction_record(record) current_transaction.add_record(record) end
Begins the transaction (and turns off auto-committing).
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 311 def begin_db_transaction() 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.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 325 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).
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 330 def commit_db_transaction() end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 344 def default_sequence_name(table, column) nil end
Executes the delete statement and returns the number of rows affected.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 178 def delete(arel, name = nil, binds = []) sql, binds = to_sql_and_binds(arel, binds) exec_delete(sql, name, binds) end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 376 def empty_insert_statement_value(primary_key = nil) "DEFAULT VALUES" 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.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 141 def exec_delete(sql, name = nil, binds = []) exec_query(sql, name, 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.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 133 def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil) sql, binds = sql_for_insert(sql, pk, binds) exec_query(sql, name, binds) end
Executes sql
statement in the context of this connection using binds
as the bind substitutes. name
is logged along with the executed sql
statement.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 126 def exec_query(sql, name = "SQL", binds = [], prepare: false) raise NotImplementedError 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.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 148 def exec_update(sql, name = nil, binds = []) exec_query(sql, name, binds) end
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.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 119 def execute(sql, name = nil) raise NotImplementedError end
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 lib/active_record/connection_adapters/abstract/database_statements.rb, line 164 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_set` that leverages bulk SQL insert. We keep this method to provide fallback for databases like sqlite that do not support bulk inserts.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 358 def insert_fixture(fixture, table_name) execute(build_fixture_sql(Array.wrap(fixture), table_name), "Fixture Insert") end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 362 def insert_fixtures_set(fixture_set, tables_to_delete = []) fixture_inserts = build_fixture_statements(fixture_set) table_deletes = tables_to_delete.map { |table| "DELETE FROM #{quote_table_name(table)}" } statements = table_deletes + fixture_inserts with_multi_statements do disable_referential_integrity do transaction(requires_new: true) do execute_batch(statements, "Fixtures Load") end end end end
Set the sequence to the max value of the table's column.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 349 def reset_sequence!(table, column, sequence = nil) # Do nothing by default. Implement for PostgreSQL, Oracle, ... end
Rolls back the transaction (and turns on auto-committing). Must be done if the transaction block raises an exception or returns false.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 334 def rollback_db_transaction exec_rollback_db_transaction end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 340 def rollback_to_savepoint(name = nil) exec_rollback_to_savepoint(name) 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.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 386 def sanitize_limit(limit) if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral) limit else Integer(limit) end end
Returns an ActiveRecord::Result
instance.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 59 def select_all(arel, name = nil, binds = [], preparable: nil) arel = arel_from_relation(arel) sql, binds = to_sql_and_binds(arel, binds) if preparable.nil? preparable = prepared_statements ? visitor.preparable : false 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.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 76 def select_one(arel, name = nil, binds = []) select_all(arel, name, binds).first end
Returns an array of arrays containing the field values. Order is the same as that returned by columns
.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 93 def select_rows(arel, name = nil, binds = []) select_all(arel, name, binds).rows end
Returns a single value from a record
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 81 def select_value(arel, name = nil, binds = []) single_value_from_rows(select_rows(arel, name, binds)) 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]
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 87 def select_values(arel, name = nil, binds = []) select_rows(arel, name, binds).map(&:first) end
Converts an arel AST to SQL
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 12 def to_sql(arel_or_sql_string, binds = []) sql, _ = to_sql_and_binds(arel_or_sql_string, binds) sql 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: 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 lib/active_record/connection_adapters/abstract/database_statements.rb, line 273 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 lib/active_record/connection_adapters/abstract/database_statements.rb, line 313 def transaction_isolation_levels { read_uncommitted: "READ UNCOMMITTED", read_committed: "READ COMMITTED", repeatable_read: "REPEATABLE READ", serializable: "SERIALIZABLE" } end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 292 def transaction_open? current_transaction.open? end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 306 def transaction_state current_transaction.state end
Executes the truncate statement.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 184 def truncate(table_name, name = nil) execute(build_truncate_statement(table_name), name) end
Executes the update statement and returns the number of rows affected.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 172 def update(arel, name = nil, binds = []) sql, binds = to_sql_and_binds(arel, binds) exec_update(sql, name, binds) end
Determines whether the SQL statement is a write query.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 110 def write_query?(sql) raise NotImplementedError end
Private Instance Methods
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 509 def arel_from_relation(relation) if relation.is_a?(Relation) relation.arel else relation end end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 419 def build_fixture_sql(fixtures, table_name) columns = schema_cache.columns_hash(table_name) values_list = 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) with_yaml_fallback(type.serialize(fixture[name])) else default_insert_value(column) end end end table = Arel::Table.new(table_name) manager = Arel::InsertManager.new manager.into(table) if values_list.size == 1 values = values_list.shift new_values = [] columns.each_key.with_index { |column, i| unless values[i].equal?(DEFAULT_INSERT_VALUE) new_values << values[i] manager.columns << table[column] end } values_list << new_values else columns.each_key { |column| manager.columns << table[column] } end manager.values = manager.create_values_list(values_list) visitor.compile(manager.ast) end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 462 def build_fixture_statements(fixture_set) fixture_set.map do |table_name, fixtures| next if fixtures.empty? build_fixture_sql(fixtures, table_name) end.compact end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 469 def build_truncate_statement(table_name) "TRUNCATE TABLE #{quote_table_name(table_name)}" end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 473 def build_truncate_statements(table_names) table_names.map do |table_name| build_truncate_statement(table_name) end end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 483 def combine_multi_statements(total_sql) total_sql.join(";\n") end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 415 def default_insert_value(column) DEFAULT_INSERT_VALUE end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 406 def execute_batch(statements, name = nil) statements.each do |statement| execute(statement, name) end end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 500 def last_inserted_id(result) single_value_from_rows(result.rows) end
Returns an ActiveRecord::Result
instance.
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 488 def select(sql, name = nil, binds = []) exec_query(sql, name, binds, prepare: false) end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 492 def select_prepared(sql, name = nil, binds = []) exec_query(sql, name, binds, prepare: true) end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 504 def single_value_from_rows(rows) row = rows.first row && row.first end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 496 def sql_for_insert(sql, pk, binds) [sql, binds] end
# File lib/active_record/connection_adapters/abstract/database_statements.rb, line 479 def with_multi_statements yield end