kubawieczorek

connection.setAutoCommit(false);
connection.setSavepoint();

try (PreparedStatement selectAccountStatementFrom = connection.prepareStatement(SELECT_ACCOUNT_BY_OWNER_SQL);
     PreparedStatement selectAccountStatementTo = connection.prepareStatement(SELECT_ACCOUNT_BY_OWNER_SQL);
     PreparedStatement updateAccountStatement = connection.prepareStatement(UPDATE_ACCOUNT_SQL)) {

    ResultSet accountFrom = findAccount(bankTransfer.getFrom(), selectAccountStatementFrom);
    ResultSet accountTo = findAccount(bankTransfer.getTo(), selectAccountStatementTo);
    BigDecimal amount = bankTransfer.getAmount();

kubawieczorek

 try (PreparedStatement selectAccountStatementFrom = connection.prepareStatement(SELECT_ACCOUNT_BY_OWNER_SQL);
      PreparedStatement selectAccountStatementTo = connection.prepareStatement(SELECT_ACCOUNT_BY_OWNER_SQL);
      PreparedStatement updateAccountStatement = connection.prepareStatement(UPDATE_ACCOUNT_SQL)) {

  ResultSet accountFrom = findAccount(bankTransfer.getFrom(), selectAccountStatementFrom);
  ResultSet accountTo = findAccount(bankTransfer.getTo(), selectAccountStatementTo);
  BigDecimal amount = bankTransfer.getAmount();

  if (dataPresent(accountFrom, accountTo)) {
      if (sufficientAccountBalance(amount, accountFrom)) {

kubawieczorek

UPDATE employees
	SET payment=payment + 500

kubawieczorek

SELECT locktype, mode, query FROM pg_locks pl 
	LEFT JOIN pg_stat_activity psa ON pl.pid = psa.pid 
	JOIN pg_class pc ON pc.oid = pl.relation 
	WHERE pc.relname = 'employees'

kubawieczorek

VACUUM FULL employees;

kubawieczorek

UPDATE employees
	SET payment=payment + 500
	WHERE employeeid = 1;

kubawieczorek

BEGIN;

SELECT xmin, xmax, employeeid, lastname, firstname, payment
	FROM employees;

kubawieczorek

BEGIN;

UPDATE employees
	SET payment = payment + 1000
	WHERE employeeid = 1;

kubawieczorek

SELECT xmin, xmax, employeeid, lastname, firstname, payment
	FROM employees WHERE firstname = 'Carl';

kubawieczorek

COMMIT;