The Ruby DBI module provides a couple of ways to perform
transactions, although both of them rely on manipulation of
auto-commit mode. One approach uses a begin/rescue
block, and you invoke the
commit
and rollback
methods
explicitly:
begin dbh['AutoCommit'] = false dbh.do("UPDATE money SET amt = amt - 6 WHERE name = 'Eve'") dbh.do("UPDATE money SET amt = amt + 6 WHERE name = 'Ida'") dbh.commit dbh['AutoCommit'] = true rescue DBI::DatabaseError => e puts "Transaction failed" puts "#{e.err}: #{e.errstr}" begin # empty exception handler in case rollback fails dbh.rollback dbh['AutoCommit'] = true rescue end end
Ruby also supports a transaction
method, which is associated with a code block and which commits
or rolls back automatically depending on whether the code block
succeeds or fails:
begin dbh['AutoCommit'] = false dbh.transaction do |dbh| dbh.do("UPDATE money SET amt = amt - 6 WHERE name = 'Eve'") dbh.do("UPDATE money SET amt = amt + 6 WHERE name = 'Ida'") end dbh['AutoCommit'] = true rescue DBI::DatabaseError => e puts "Transaction failed" puts "#{e.err}: #{e.errstr}" dbh['AutoCommit'] = true end
With the transaction
method,
there is no need to invoke commit
or rollback
explicitly yourself.
transaction
does raise an exception
if it rolls back, so the example still uses a
begin/rescue
block
for error detection.
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