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Appends LIMIT
and OFFSET
options to an SQL
statement, or some SQL fragment that has the same semantics as LIMIT and
OFFSET.
options
must be a Hash which
contains a :limit
option and an :offset
option.
This method modifies the sql
parameter.
This method is deprecated!! Stop using it!
Examples
add_limit_offset!('SELECT * FROM suppliers', {:limit => 10, :offset => 50})
generates
SELECT * FROM suppliers LIMIT 10 OFFSET 50
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 271 def add_limit_offset!(sql, options) if limit = options[:limit] sql << " LIMIT #{sanitize_limit(limit)}" end if offset = options[:offset] sql << " OFFSET #{offset.to_i}" end sql end
Register a record with the current transaction so that its after_commit and after_rollback callbacks can be called.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 242 def add_transaction_record(record) last_batch = @_current_transaction_records.last last_batch << record if last_batch end
Begins the transaction (and turns off auto-committing).
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 248 def begin_db_transaction() end
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 309 def case_sensitive_equality_operator "=" end
Commits the transaction (and turns on auto-committing).
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 251 def commit_db_transaction() end
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 282 def default_sequence_name(table, column) nil end
Executes the delete statement and returns the number of rows affected.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 100 def delete(arel, name = nil, binds = []) exec_delete(to_sql(arel), name, binds) end
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 305 def empty_insert_statement_value "VALUES(DEFAULT)" end
Executes delete sql
statement in the context of this
connection using binds
as the bind substitutes.
name
is the logged along with the executed sql
statement.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 69 def exec_delete(sql, name, 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 the logged along with the executed sql
statement.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 62 def exec_insert(sql, name, 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.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 56 def exec_query(sql, name = 'SQL', binds = []) end
Executes update sql
statement in the context of this
connection using binds
as the bind substitutes.
name
is the logged along with the executed sql
statement.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 76 def exec_update(sql, name, binds) exec_query(sql, name, binds) end
Executes the SQL statement in the context of this connection.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 49 def execute(sql, name = nil) 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
.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 88 def insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = []) sql, binds = sql_for_insert(to_sql(arel), pk, id_value, sequence_name, binds) value = exec_insert(sql, name, binds) 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).
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 293 def insert_fixture(fixture, table_name) columns = Hash[columns(table_name).map { |c| [c.name, c] }] 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
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 313 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
Checks whether there is currently no transaction active. This is done by querying the database driver, and does not use the transaction house-keeping information recorded by increment_open_transactions and friends.
Returns true if there is no transaction active, false if there is a transaction active, and nil if this information is unknown.
Not all adapters supports transaction state introspection. Currently, only the PostgreSQL adapter supports this.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 114 def outside_transaction? nil end
Set the sequence to the max value of the table’s column.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 287 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.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 255 def rollback_db_transaction() 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.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 326 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
Returns an array of record hashes with the column names as keys and column values as values.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 17 def select_all(arel, name = nil, binds = []) select(to_sql(arel), name, binds) end
Returns a record hash with the column names as keys and column values as values.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 23 def select_one(arel, name = nil) result = select_all(arel, name) result.first if result end
Returns an array of arrays containing the field values. Order is the same
as that returned by columns
.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 44 def select_rows(sql, name = nil) end
Returns a single value from a record
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 29 def select_value(arel, name = nil) if result = select_one(arel, name) 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]
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 37 def select_values(arel, name = nil) result = select_rows(to_sql(arel), name) result.map { |v| v[0] } end
Returns true
when the connection adapter supports prepared
statement caching, otherwise returns false
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 120 def supports_statement_cache? false end
Converts an arel AST to SQL
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 7 def to_sql(arel) if arel.respond_to?(:ast) visitor.accept(arel.ast) else arel end 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/5.0/en/savepoints.html Savepoints are supported by MySQL and PostgreSQL, but not SQLite3.
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
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 166 def transaction(options = {}) options.assert_valid_keys :requires_new, :joinable last_transaction_joinable = defined?(@transaction_joinable) ? @transaction_joinable : nil if options.has_key?(:joinable) @transaction_joinable = options[:joinable] else @transaction_joinable = true end requires_new = options[:requires_new] || !last_transaction_joinable transaction_open = false @_current_transaction_records ||= [] begin if block_given? if requires_new || open_transactions == 0 if open_transactions == 0 begin_db_transaction elsif requires_new create_savepoint end increment_open_transactions transaction_open = true @_current_transaction_records.push([]) end yield end rescue Exception => database_transaction_rollback if transaction_open && !outside_transaction? transaction_open = false decrement_open_transactions if open_transactions == 0 rollback_db_transaction rollback_transaction_records(true) else rollback_to_savepoint rollback_transaction_records(false) end end raise unless database_transaction_rollback.is_a?(ActiveRecord::Rollback) end ensure @transaction_joinable = last_transaction_joinable if outside_transaction? @open_transactions = 0 elsif transaction_open decrement_open_transactions begin if open_transactions == 0 commit_db_transaction commit_transaction_records else release_savepoint save_point_records = @_current_transaction_records.pop unless save_point_records.blank? @_current_transaction_records.push([]) if @_current_transaction_records.empty? @_current_transaction_records.last.concat(save_point_records) end end rescue Exception => database_transaction_rollback if open_transactions == 0 rollback_db_transaction rollback_transaction_records(true) else rollback_to_savepoint rollback_transaction_records(false) end raise end end end
Executes the update statement and returns the number of rows affected.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 95 def update(arel, name = nil, binds = []) exec_update(to_sql(arel), name, binds) end
Send a commit message to all records after they have been committed.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 391 def commit_transaction_records #:nodoc records = @_current_transaction_records.flatten @_current_transaction_records.clear unless records.blank? records.uniq.each do |record| begin record.committed! rescue Exception => e record.logger.error(e) if record.respond_to?(:logger) && record.logger end end end end
Executes the delete statement and returns the number of rows affected.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 365 def delete_sql(sql, name = nil) update_sql(sql, name) end
Returns the last auto-generated ID from the affected table.
Source: show
# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 354 def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil) execute(sql, name) id_value end
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 409 def last_inserted_id(result) row = result.rows.first row && row.first end
Send a rollback message to all records after they have been rolled back. If rollback is false, only rollback records since the last save point.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 371 def rollback_transaction_records(rollback) #:nodoc if rollback records = @_current_transaction_records.flatten @_current_transaction_records.clear else records = @_current_transaction_records.pop end unless records.blank? records.uniq.each do |record| begin record.rolledback!(rollback) rescue Exception => e record.logger.error(e) if record.respond_to?(:logger) && record.logger end end end end
Returns an array of record hashes with the column names as keys and column values as values.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 349 def select(sql, name = nil, binds = []) end
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 405 def sql_for_insert(sql, pk, id_value, sequence_name, binds) [sql, binds] end
Executes the update statement and returns the number of rows affected.
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# File activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb, line 360 def update_sql(sql, name = nil) execute(sql, name) end