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require 'socket'
require 'digest'
require 'digest/sha2'
module DataObjects
class Transaction
# The host name. Note, this relies on the host name being configured and resolvable using DNS
HOST = "#{Socket::gethostbyname(Socket::gethostname)[0]}" rescue "localhost"
@@counter = 0
# The connection object allocated for this transaction
attr_reader :connection
# A unique ID for this transaction
attr_reader :id
# Instantiate the Transaction subclass that's appropriate for this uri scheme
def self.create_for_uri(uri)
uri = uri.is_a?(String) ? URI::parse(uri) : uri
DataObjects.const_get(uri.scheme.capitalize)::Transaction.new(uri)
end
#
# Creates a Transaction bound to a connection for the given DataObjects::URI
#
def initialize(uri, connection = nil)
@connection = connection || DataObjects::Connection.new(uri)
# PostgreSQL can't handle the full 64 bytes. This should be enough for everyone.
@id = Digest::SHA256.hexdigest("#{HOST}:#{$$}:#{Time.now.to_f}:#{@@counter += 1}")[0..-2]
end
# Close the connection for this Transaction
def close
@connection.close
end
def begin
run "BEGIN"
end
def commit
run "COMMIT"
end
def rollback
run "ROLLBACK"
end
def prepare; not_implemented; end;
def begin_prepared; not_implemented; end;
def commit_prepared; not_implemented; end;
def rollback_prepared; not_implemented; end;
def prepare; not_implemented; end;
protected
def run(cmd)
connection.create_command(cmd).execute_non_query
end
private
def not_implemented
raise NotImplementedError
end
end # class Transaction
class SavePoint < Transaction
# We don't bounce through DO::<Adapter/scheme>::SavePoint because there
# doesn't appear to be any custom SQL to support this.
def self.create_for_uri(uri, connection)
uri = uri.is_a?(String) ? URI::parse(uri) : uri
DataObjects::SavePoint.new(uri, connection)
end
# SavePoints can only occur in the context of a Transaction, thus they
# re-use TXN's connection (which was acquired from the connection pool
# legitimately via DO::Connection.new). We no-op #close in SP because
# calling DO::Connection#close will release the connection back into the
# pool (before the top-level Transaction might be done with it).
def close
# no-op
end
def begin
run %{SAVEPOINT "#{@id}"}
end
def commit
run %{RELEASE SAVEPOINT "#{@id}"}
end
def rollback
run %{ROLLBACK TO SAVEPOINT "#{@id}"}
end
end # class SavePoint
end
|
