Module: ActiveRecord::ConnectionAdapters::DatabaseStatements
- Included in:
- AbstractAdapter
- Defined in:
- lib/active_record/connection_adapters/abstract/database_statements.rb
Instance Attribute Summary collapse
-
#transaction_manager ⇒ Object
readonly
:nodoc:.
Instance Method Summary collapse
-
#add_transaction_record(record) ⇒ Object
Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
-
#begin_db_transaction ⇒ Object
Begins the transaction (and turns off auto-committing).
-
#begin_isolated_db_transaction(isolation) ⇒ Object
Begins the transaction with the isolation level set.
-
#cacheable_query(klass, arel) ⇒ Object
This is used in the StatementCache object.
-
#commit_db_transaction ⇒ Object
Commits the transaction (and turns on auto-committing).
- #default_sequence_name(table, column) ⇒ Object
-
#delete(arel, name = nil, binds = []) ⇒ Object
Executes the delete statement and returns the number of rows affected.
- #empty_insert_statement_value ⇒ Object
-
#exec_delete(sql, name = nil, binds = []) ⇒ Object
Executes delete
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil) ⇒ Object
Executes insert
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_query(sql, name = "SQL", binds = [], prepare: false) ⇒ Object
Executes
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_rollback_db_transaction ⇒ Object
:nodoc:.
-
#exec_update(sql, name = nil, binds = []) ⇒ Object
Executes update
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#execute(sql, name = nil) ⇒ Object
Executes the SQL statement in the context of this connection and returns the raw result from the connection adapter.
- #initialize ⇒ Object
-
#insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = []) ⇒ Object
(also: #create)
Executes an INSERT query and returns the new record’s ID.
-
#insert_fixture(fixture, table_name) ⇒ Object
Inserts the given fixture into the table.
-
#join_to_update(update, select, key) ⇒ Object
(also: #join_to_delete)
The default strategy for an UPDATE with joins is to use a subquery.
-
#query(sql, name = nil) ⇒ Object
:nodoc:.
-
#query_value(sql, name = nil) ⇒ Object
:nodoc:.
-
#query_values(sql, name = nil) ⇒ Object
:nodoc:.
-
#reset_sequence!(table, column, sequence = nil) ⇒ Object
Set the sequence to the max value of the table’s column.
-
#reset_transaction ⇒ Object
:nodoc:.
-
#rollback_db_transaction ⇒ Object
Rolls back the transaction (and turns on auto-committing).
- #rollback_to_savepoint(name = nil) ⇒ Object
-
#sanitize_limit(limit) ⇒ Object
Sanitizes the given LIMIT parameter in order to prevent SQL injection.
-
#select_all(arel, name = nil, binds = [], preparable: nil) ⇒ Object
Returns an ActiveRecord::Result instance.
-
#select_one(arel, name = nil, binds = []) ⇒ Object
Returns a record hash with the column names as keys and column values as values.
-
#select_rows(arel, name = nil, binds = []) ⇒ Object
Returns an array of arrays containing the field values.
-
#select_value(arel, name = nil, binds = []) ⇒ Object
Returns a single value from a record.
-
#select_values(arel, name = nil, binds = []) ⇒ 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].
-
#supports_statement_cache? ⇒ Boolean
Returns
true
when the connection adapter supports prepared statement caching, otherwise returnsfalse
. -
#to_sql(arel, binds = []) ⇒ Object
Converts an arel AST to SQL.
-
#transaction(requires_new: nil, isolation: nil, joinable: true) ⇒ Object
Runs the given block in a database transaction, and returns the result of the block.
- #transaction_isolation_levels ⇒ Object
- #transaction_open? ⇒ Boolean
- #transaction_state ⇒ Object
-
#truncate(table_name, name = nil) ⇒ Object
Executes the truncate statement.
-
#update(arel, name = nil, binds = []) ⇒ Object
Executes the update statement and returns the number of rows affected.
Instance Attribute Details
#transaction_manager ⇒ Object (readonly)
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 241 def transaction_manager @transaction_manager end |
Instance Method Details
#add_transaction_record(record) ⇒ Object
Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 255 def add_transaction_record(record) current_transaction.add_record(record) end |
#begin_db_transaction ⇒ Object
Begins the transaction (and turns off auto-committing).
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 264 def begin_db_transaction() end |
#begin_isolated_db_transaction(isolation) ⇒ Object
Begins the transaction with the isolation level set. Raises an error by default; adapters that support setting the isolation level should implement this method.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 278 def begin_isolated_db_transaction(isolation) raise ActiveRecord::TransactionIsolationError, "adapter does not support setting transaction isolation" end |
#cacheable_query(klass, arel) ⇒ Object
This is used in the StatementCache object. It returns an object that can be used to query the database repeatedly.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 21 def cacheable_query(klass, arel) # :nodoc: collected = visitor.accept(arel.ast, collector) if prepared_statements klass.query(collected.value) else klass.partial_query(collected.value) end end |
#commit_db_transaction ⇒ Object
Commits the transaction (and turns on auto-committing).
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 283 def commit_db_transaction() end |
#default_sequence_name(table, column) ⇒ Object
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 297 def default_sequence_name(table, column) nil end |
#delete(arel, name = nil, binds = []) ⇒ Object
Executes the delete statement and returns the number of rows affected.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 144 def delete(arel, name = nil, binds = []) exec_delete(to_sql(arel, binds), name, binds) end |
#empty_insert_statement_value ⇒ Object
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 332 def empty_insert_statement_value "DEFAULT VALUES" end |
#exec_delete(sql, name = nil, binds = []) ⇒ Object
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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 108 def exec_delete(sql, name = nil, binds = []) exec_query(sql, name, binds) end |
#exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil) ⇒ Object
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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 100 def exec_insert(sql, name = nil, binds = [], pk = nil, sequence_name = nil) sql, binds = sql_for_insert(sql, pk, nil, sequence_name, binds) exec_query(sql, name, binds) end |
#exec_query(sql, name = "SQL", binds = [], prepare: false) ⇒ Object
Executes sql
statement in the context of this connection using binds
as the bind substitutes. name
is logged along with the executed sql
statement.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 93 def exec_query(sql, name = "SQL", binds = [], prepare: false) raise NotImplementedError end |
#exec_rollback_db_transaction ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 291 def exec_rollback_db_transaction() end |
#exec_update(sql, name = nil, binds = []) ⇒ Object
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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 120 def exec_update(sql, name = nil, binds = []) exec_query(sql, name, binds) end |
#execute(sql, name = nil) ⇒ Object
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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 86 def execute(sql, name = nil) raise NotImplementedError end |
#initialize ⇒ Object
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 4 def initialize super reset_transaction end |
#insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = []) ⇒ Object Also known as: create
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
.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 132 def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = []) value = exec_insert(to_sql(arel, binds), name, binds, pk, sequence_name) id_value || last_inserted_id(value) 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).
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 308 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 key_list = fixture.keys.map { |name| quote_column_name(name) } value_list = binds.map(&:value_for_database).map do |value| begin quote(value) rescue TypeError quote(YAML.dump(value)) end end execute "INSERT INTO #{quote_table_name(table_name)} (#{key_list.join(', ')}) VALUES (#{value_list.join(', ')})", "Fixture Insert" end |
#join_to_update(update, select, key) ⇒ Object Also known as: join_to_delete
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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 353 def join_to_update(update, select, key) # :nodoc: subselect = subquery_for(key, select) update.where key.in(subselect) end |
#query(sql, name = nil) ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 77 def query(sql, name = nil) # :nodoc: exec_query(sql, name).rows end |
#query_value(sql, name = nil) ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 69 def query_value(sql, name = nil) # :nodoc: single_value_from_rows(query(sql, name)) end |
#query_values(sql, name = nil) ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 73 def query_values(sql, name = nil) # :nodoc: query(sql, name).map(&:first) end |
#reset_sequence!(table, column, sequence = nil) ⇒ Object
Set the sequence to the max value of the table’s column.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 302 def reset_sequence!(table, column, sequence = nil) # Do nothing by default. Implement for PostgreSQL, Oracle, ... end |
#reset_transaction ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 249 def reset_transaction #:nodoc: @transaction_manager = ConnectionAdapters::TransactionManager.new(self) 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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 287 def rollback_db_transaction exec_rollback_db_transaction end |
#rollback_to_savepoint(name = nil) ⇒ Object
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 293 def rollback_to_savepoint(name = nil) exec_rollback_to_savepoint(name) 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 an Arel SQL literal.
Returns Integer and Arel::Nodes::SqlLiteral limits as is.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 342 def sanitize_limit(limit) if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral) limit else Integer(limit) end end |
#select_all(arel, name = nil, binds = [], preparable: nil) ⇒ Object
Returns an ActiveRecord::Result instance.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 31 def select_all(arel, name = nil, binds = [], preparable: nil) arel, binds = binds_from_relation arel, binds sql = to_sql(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 |
#select_one(arel, name = nil, binds = []) ⇒ Object
Returns a record hash with the column names as keys and column values as values.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 48 def select_one(arel, name = nil, binds = []) select_all(arel, name, binds).first end |
#select_rows(arel, name = nil, binds = []) ⇒ Object
Returns an array of arrays containing the field values. Order is the same as that returned by columns
.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 65 def select_rows(arel, name = nil, binds = []) select_all(arel, name, binds).rows end |
#select_value(arel, name = nil, binds = []) ⇒ Object
Returns a single value from a record
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 53 def select_value(arel, name = nil, binds = []) single_value_from_rows(select_rows(arel, name, binds)) end |
#select_values(arel, name = nil, binds = []) ⇒ 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]
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 59 def select_values(arel, name = nil, binds = []) select_rows(arel, name, binds).map(&:first) end |
#supports_statement_cache? ⇒ Boolean
Returns true
when the connection adapter supports prepared statement caching, otherwise returns false
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 150 def supports_statement_cache? false end |
#to_sql(arel, binds = []) ⇒ Object
Converts an arel AST to SQL
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 10 def to_sql(arel, binds = []) if arel.respond_to?(:ast) collected = visitor.accept(arel.ast, collector) collected.compile(binds, self).freeze else arel.dup.freeze end end |
#transaction(requires_new: nil, isolation: nil, joinable: true) ⇒ 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/5.7/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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 228 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 |
#transaction_isolation_levels ⇒ Object
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 266 def transaction_isolation_levels { read_uncommitted: "READ UNCOMMITTED", read_committed: "READ COMMITTED", repeatable_read: "REPEATABLE READ", serializable: "SERIALIZABLE" } end |
#transaction_open? ⇒ Boolean
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 245 def transaction_open? current_transaction.open? end |
#transaction_state ⇒ Object
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 259 def transaction_state current_transaction.state end |
#truncate(table_name, name = nil) ⇒ Object
Executes the truncate statement.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 113 def truncate(table_name, name = nil) raise NotImplementedError end |
#update(arel, name = nil, binds = []) ⇒ Object
Executes the update statement and returns the number of rows affected.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 139 def update(arel, name = nil, binds = []) exec_update(to_sql(arel, binds), name, binds) end |