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From "Kathey Marsden (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-5671) NsTest does not run on trunk do multiple issues stemming from concurrency improvements
Date Thu, 29 Mar 2012 22:17:25 GMT

    [ https://issues.apache.org/jira/browse/DERBY-5671?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13241862#comment-13241862
] 

Kathey Marsden commented on DERBY-5671:
---------------------------------------

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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