Philip Wilder wrote: > Hello, > > As I am sure most of you are aware Kathy and I have been working on > DERBY-213 (http://issues.apache.org/jira/browse/DERBY-213) for while > now. We have recently put the finishing touches on a promising patch > when I ran into a little snag. Somehow while looking over the code I > managed to overlook this comment until recently: > > /* > * From Connection.setAutoCommit() javadoc: > * The commit occurs when the statement completes or the next execute > occurs, whichever comes first. > * In the case of statements returning a ResultSet object, *the > statement completes when the > * last row of the ResultSet object has been retrieved* or the > ResultSet object has been closed. > */ > > This may or may not be a problem. The nature of our change to the client > side code is to make sure the closeX() method is only called on errors > or explicit close requests, a closed server side ResultSet or exceptions > rather then the first time the .next() method returns false. However at > the moment all of the autocommit logic is in the closeX() method, so by > altering when the closeX() function is called we are altering the > autocommit logic. This comment would seem to indicate that we must by > necessity commit any changes to the ResultSet when the last row of the > ResultSet is retrieved but I'm not sure what there is to commit. I > believe all of the .getXXX() calls to the ResultSet are readOnly, > .updateXXX() calls must be finalized with the UpdateRow() method before > the .next() method is called or the updates will be discarded and insert > functionality is not supported by the Client Driver. > > So are we doing any harm by releasing this patch or is this the fix we > are looking for? The proposed changes do not seem to cause any problems > in the derbyall suite but this may be a lapse in the test suite rather > then good design decisions on our part.
A commit 'commits the transaction', which is a broader statement than 'commits the changes'. In most isolation levels read locks can be held until the end of the transaction, and are released by the commit. Thus even in a read-only transaction, commits are required. Does that help? Dan.
