Module: ActiveRecord::ConnectionAdapters::DatabaseStatements

### Home Classes Methods

### In Files

- lib/active_record/connection_adapters/abstract/database_statements.rb

### Methods

- #add_transaction_record
- #begin_db_transaction
- #case_sensitive_equality_operator
- #commit_db_transaction
- #commit_transaction_records
- #default_sequence_name
- #delete
- #delete_sql
- #empty_insert_statement_value
- #exec_delete
- #exec_insert
- #exec_query
- #exec_update
- #execute
- #insert
- #insert_fixture
- #insert_sql
- #last_inserted_id
- #limited_update_conditions
- #outside_transaction?
- #reset_sequence!
- #rollback_db_transaction
- #rollback_transaction_records
- #sanitize_limit
- #select
- #select_all
- #select_one
- #select_rows
- #select_value
- #select_values
- #sql_for_insert
- #supports_statement_cache?
- #to_sql
- #transaction
- #update
- #update_sql

### Files

- README.rdoc

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No matching classes.

# ActiveRecord::ConnectionAdapters::DatabaseStatements

### Public Instance Methods

add_transaction_record(record) click to toggle source

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 242
    def add_transaction_record(record)
      last_batch = @_current_transaction_records.last
      last_batch << record if last_batch
    end

begin_db_transaction() click to toggle source

Begins the transaction (and turns off auto-committing).

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 248
    def begin_db_transaction()    end

case_sensitive_equality_operator() click to toggle source

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 284
    def case_sensitive_equality_operator
      "="
    end

commit_db_transaction() click to toggle source

Commits the transaction (and turns on auto-committing).

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 251
    def commit_db_transaction()   end

default_sequence_name(table, column) click to toggle source

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 257
    def default_sequence_name(table, column)
      nil
    end

delete(arel, name = nil, binds = []) click to toggle source

Executes the delete statement and returns the number of rows affected.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 100
    def delete(arel, name = nil, binds = [])
      exec_delete(to_sql(arel, binds), name, binds)
    end

empty_insert_statement_value() click to toggle source

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 280
    def empty_insert_statement_value
      "VALUES(DEFAULT)"
    end

exec_delete(sql, name, binds) click to toggle source

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.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 69
    def exec_delete(sql, name, binds)
      exec_query(sql, name, binds)
    end

exec_insert(sql, name, binds) click to toggle source

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.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 62
    def exec_insert(sql, name, binds)
      exec_query(sql, name, binds)
    end

exec_query(sql, name = 'SQL', binds = []) click to toggle source

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 56
    def exec_query(sql, name = 'SQL', binds = [])
    end

exec_update(sql, name, binds) click to toggle source

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.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 76
    def exec_update(sql, name, binds)
      exec_query(sql, name, binds)
    end

execute(sql, name = nil) click to toggle source

Executes the SQL statement in the context of this connection.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 49
    def execute(sql, name = nil)
    end

insert(arel, name = nil, pk = nil, id_value = nil, sequence_name = nil, binds = []) click to toggle source

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`.

    # File 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, binds), pk, id_value, sequence_name, binds)
      value      = exec_insert(sql, name, binds)
      id_value || last_inserted_id(value)
    end

insert_fixture(fixture, table_name) click to toggle source

Inserts the given fixture into the table. Overridden in adapters that require something beyond a simple insert (eg. Oracle).

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 268
    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

limited_update_conditions(where_sql, quoted_table_name, quoted_primary_key) click to toggle source

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 288
    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

outside_transaction?() click to toggle source

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.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 114
    def outside_transaction?
      nil
    end

reset_sequence!(table, column, sequence = nil) click to toggle source

Set the sequence to the max value of the table's column.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 262
    def reset_sequence!(table, column, sequence = nil)
      # Do nothing by default. Implement for PostgreSQL, Oracle, ...
    end

rollback_db_transaction() click to toggle source

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 255
    def rollback_db_transaction() end

sanitize_limit(limit) click to toggle source

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.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 301
    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

select_all(arel, name = nil, binds = []) click to toggle source

Returns an array of record hashes with the column names as keys and column values as values.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 17
    def select_all(arel, name = nil, binds = [])
      select(to_sql(arel, binds), name, binds)
    end

select_one(arel, name = nil) click to toggle source

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 23
    def select_one(arel, name = nil)
      result = select_all(arel, name)
      result.first if result
    end

select_rows(sql, name = nil) click to toggle source

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 44
    def select_rows(sql, name = nil)
    end

select_value(arel, name = nil) click to toggle source

Returns a single value from a record

    # File 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

select_values(arel, name = nil) click to toggle source

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 37
    def select_values(arel, name = nil)
      result = select_rows(to_sql(arel, []), name)
      result.map { |v| v[0] }
    end

supports_statement_cache?() click to toggle source

Returns `true` when the connection adapter supports prepared statement caching, otherwise returns `false`

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 120
    def supports_statement_cache?
      false
    end

to_sql(arel, binds = []) click to toggle source

Converts an arel AST to SQL

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 5
    def to_sql(arel, binds = [])
      if arel.respond_to?(:ast)
        visitor.accept(arel.ast) do
          quote(*binds.shift.reverse)
        end
      else
        arel
      end
    end

transaction(options = {}) click to toggle source

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, 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

    # File 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

update(arel, name = nil, binds = []) click to toggle source

Executes the update statement and returns the number of rows affected.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 95
    def update(arel, name = nil, binds = [])
      exec_update(to_sql(arel, binds), name, binds)
    end

### Protected Instance Methods

commit_transaction_records() click to toggle source

Send a commit message to all records after they have been committed.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 366
    def commit_transaction_records
      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

delete_sql(sql, name = nil) click to toggle source

Executes the delete statement and returns the number of rows affected.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 340
    def delete_sql(sql, name = nil)
      update_sql(sql, name)
    end

insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil) click to toggle source

Returns the last auto-generated ID from the affected table.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 329
    def insert_sql(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
      execute(sql, name)
      id_value
    end

last_inserted_id(result) click to toggle source

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 384
    def last_inserted_id(result)
      row = result.rows.first
      row && row.first
    end

rollback_transaction_records(rollback) click to toggle source

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.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 346
    def rollback_transaction_records(rollback)
      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

select(sql, name = nil, binds = []) click to toggle source

Returns an array of record hashes with the column names as keys and column values as values.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 324
    def select(sql, name = nil, binds = [])
    end

sql_for_insert(sql, pk, id_value, sequence_name, binds) click to toggle source

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 380
    def sql_for_insert(sql, pk, id_value, sequence_name, binds)
      [sql, binds]
    end

update_sql(sql, name = nil) click to toggle source

Executes the update statement and returns the number of rows affected.

    # File lib/active_record/connection_adapters/abstract/database_statements.rb, line 335
    def update_sql(sql, name = nil)
      execute(sql, name)
    end

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