Re: SSI bug?

An updated patch to address this issue is attached. It fixes a couple
issues related to use of the backend-local lock table hint:

  - CheckSingleTargetForConflictsIn now correctly handles the case
    where a lock that's being held is not reflected in the local lock
    table. This fixes the assertion failure reported in this thread.

  - PredicateLockPageCombine now retains locks for the page that is
    being removed, rather than removing them. This prevents a
    potentially dangerous false-positive inconsistency where the local
    lock table believes that a lock is held, but it is actually not.

  - add some more comments documenting the times when the local lock
    table can be inconsistent with reality, as reflected in the shared
    memory table.

This patch also incorporates Kevin's changes to copy locks when
creating a new version of a tuple rather than trying to maintain a
linkage between different versions. So this is a patch that should
apply against HEAD and addresses all outstanding SSI bugs known to
Kevin or myself.

Besides the usual regression and isolation tests, I have tested this
by running DBT-2 on a 16-core machine to verify that there are no
assertion failures that only show up under concurrent access.

Dan

--
Dan R. K. Ports              MIT CSAIL                http://drkp.net/