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(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, binds) ⇒ Object
Executes delete
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_insert(sql, name, 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 = []) ⇒ Object
Executes
sql
statement in the context of this connection usingbinds
as the bind substitutes. -
#exec_rollback_db_transaction ⇒ Object
:nodoc:.
-
#exec_rollback_to_savepoint(name = nil) ⇒ Object
:nodoc:.
-
#exec_update(sql, name, 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.
- #initialize ⇒ Object
-
#insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = []) ⇒ Object
Returns the last auto-generated ID from the affected table.
-
#insert_fixture(fixture, table_name) ⇒ Object
Inserts the given fixture into the table.
-
#join_to_delete(delete, select, key) ⇒ Object
:nodoc:.
-
#join_to_update(update, select) ⇒ Object
The default strategy for an UPDATE with joins is to use a subquery.
-
#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 = []) ⇒ 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(sql, 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) ⇒ 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(options = {}) ⇒ 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 219 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 233 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 242 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 256 def begin_isolated_db_transaction(isolation) raise ActiveRecord::TransactionIsolationError, "adapter does not support setting transaction isolation" end |
#cacheable_query(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(arel) # :nodoc: if prepared_statements ActiveRecord::StatementCache.query visitor, arel.ast else ActiveRecord::StatementCache.partial_query visitor, arel.ast, collector 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 261 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 278 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 118 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 301 def empty_insert_statement_value "DEFAULT VALUES" end |
#exec_delete(sql, name, 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 82 def exec_delete(sql, name, binds) exec_query(sql, name, binds) end |
#exec_insert(sql, name, 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 75 def exec_insert(sql, name, binds, pk = nil, sequence_name = nil) exec_query(sql, name, binds) end |
#exec_query(sql, name = 'SQL', binds = []) ⇒ 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 69 def exec_query(sql, name = 'SQL', binds = []) end |
#exec_rollback_db_transaction ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 269 def exec_rollback_db_transaction() end |
#exec_rollback_to_savepoint(name = nil) ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 275 def exec_rollback_to_savepoint(name = nil) #:nodoc: end |
#exec_update(sql, name, 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 94 def exec_update(sql, name, binds) exec_query(sql, name, binds) end |
#execute(sql, name = nil) ⇒ Object
Executes the SQL statement in the context of this connection.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 62 def execute(sql, name = nil) 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
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
.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 106 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 |
#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 289 def insert_fixture(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 execute "INSERT INTO #{quote_table_name(table_name)} (#{key_list.join(', ')}) VALUES (#{value_list.join(', ')})", 'Fixture Insert' end |
#join_to_delete(delete, select, key) ⇒ Object
:nodoc:
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 334 def join_to_delete(delete, select, key) #:nodoc: subselect = subquery_for(key, select) delete.where key.in(subselect) end |
#join_to_update(update, select) ⇒ Object
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 327 def join_to_update(update, select) #:nodoc: key = update.key subselect = subquery_for(key, select) update.where key.in(subselect) 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 283 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 227 def reset_transaction #:nodoc: @transaction_manager = 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 265 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 271 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 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.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 314 def sanitize_limit(limit) if limit.is_a?(Integer) || limit.is_a?(Arel::Nodes::SqlLiteral) limit elsif limit.to_s.include?(',') Arel.sql limit.to_s.split(',').map{ |i| Integer(i) }.join(',') else Integer(limit) end end |
#select_all(arel, name = nil, binds = []) ⇒ Object
Returns an ActiveRecord::Result instance.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 30 def select_all(arel, name = nil, binds = []) arel, binds = binds_from_relation arel, binds select(to_sql(arel, binds), name, binds) 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 37 def select_one(arel, name = nil, binds = []) select_all(arel, name, binds).first end |
#select_rows(sql, 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 57 def select_rows(sql, name = nil, binds = []) 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 42 def select_value(arel, name = nil, binds = []) if result = select_one(arel, name, binds) result.values.first end end |
#select_values(arel, name = nil) ⇒ 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 50 def select_values(arel, name = nil) arel, binds = binds_from_relation arel, [] select_rows(to_sql(arel, binds), 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 124 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.dup, self) else arel end end |
#transaction(options = {}) ⇒ 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/5.0/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:
-
: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 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 which means the isolation level gets persisted outside the transaction.
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# File 'lib/active_record/connection_adapters/abstract/database_statements.rb', line 204 def transaction( = {}) .assert_valid_keys :requires_new, :joinable, :isolation 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() { 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 244 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 223 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 237 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 87 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 113 def update(arel, name = nil, binds = []) exec_update(to_sql(arel, binds), name, binds) end |