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https://issues.apache.org/jira/browse/DERBY-5671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13241862#comment-13241862
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Kathey Marsden commented on DERBY-5671:
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Thank you Rick for looking at the sequence issues and working to get nstest
running again. Looking not only at the number of issues linked to DERBY-4995
but also looking briefly at the scope and complexity of changes being
proposed, for example in DERBY-5493, I really think that sequences are not
mature and solid enough to be the basis of identity columns by default. We
need to get identity columns back to a stable state on trunk really as soon as
possible. Six months has been entirely too long for them to be in an untestable
state. I think within the next few weeks nsTest should be running cleanly
again.
If the goal is to move identity columns over to be sequence based, I think the
only safe approach considering the wide use in the field is to expose that
expose that as an optional experimental feature.
1) Restore the existing 10.8 default implementation for identity columns.
2) For 10.9, create an option which allows users to alternately try the new
implementation which defaults to false. Encourage users to test their
applications with both options and give the option an attractive performance
boosting name.
3) In an future release, after getting sufficient feedback from users using the
new option and resolving all known issues and maybe writning some additional
identity stress tests, switch the default and deprecate the opton.
4) In some far futre release deprecate the option and clean up the old code.
I don't know how intertangled the two implementations are. If they are,
perhaps the safest thing would be to back out the concurrency changes and then
start on the property based approch from scratch with the switchable goal.
> NsTest does not run on trunk do multiple issues stemming from concurrency
> improvements
> ---------------------------------------------------------------------------------------
>
> Key: DERBY-5671
> URL: https://issues.apache.org/jira/browse/DERBY-5671
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Reporter: Kathey Marsden
> Priority: Critical
>
> As I understand it at least since September 30 of last year, the system test
> NsTest has been broken on trunk. In these six months the test has not been
> runnable, so we do not know if new issues have been introduced with sequence
> generators or most importantly with auto-increment columns that are now based
> on them, which many, many applications rely upon. Even if the known
> problems are fixed later in the 10.9 release cycle and new problems are
> exposed, we won't be able to go back to any point in time to discover when
> they might be released.
> In 10.8 we coped with this problem by backing out the concurrency
> improvements (DERBY-5448) pending fixes for DERBY-5422, DERBY-5454,
> DERBY-5430. Currently none of those issues have been assigned. Since this
> has been going on now for six months, I think we urgently need to stabiliize
> auto-increment columns and get this test running again on trunk. I can see
> three possible options.
> 1) Someone with interest assign themselves to these issues and make
> significant progress over the next few weeks.
> 2) Make the concurrency improvements optional with a property which
> defaults to false (I don't know if this is practical)
> 3) Back the concurrency performance improvements out of trunk until these
> issues have been resolved and the change can be resubmitted.
> I realize that NsTest is not the easiest test to work with but it does seem
> to have found serious problems with generated columns that I think users are
> likely to hit. In the past, a similiar disregard for mailjdbc exposing a
> corruption issue meant that we actually released a bad corruption issue that
> I know hit many users of Derby before we addressed it. Autoincrement is
> widely, widely, used. We need to get it stabilized and the test running on
> trunk. Although the system tests are not particularly easy to deal with,
> they are all we have and they do find issues.
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