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https://issues.apache.org/jira/browse/DERBY-4771?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kristian Waagan updated DERBY-4771:
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Attachment: derby-4771-2c-prototype_lcc_code_dump.diff
Attaching patch 2c.
The two main changes:
a) Removed code in AlterTableConstantAction for updating statistics, and made
it use the daemon.
b) Removed status tracking code in TableDescriptor/statistics object.
The removal of code for (b) may cause some extra calls to the daemon, and the
scheduling requests will be rejected. I'm not sure how critical this is yet,
which is why I decided to remove the code. Maybe a more light-weight mechanism
can be re-added later.
One major concern I have right now, is how to use the dependency system.
When should the invalidation request be performed?
Does it have to be before the statistics have been generated, or can it be done
afterwards?
If the table is large, it may take a long time from the invalidation request is
performed until the index(es) has been scanned and the new statistics added to
the system tables.
I also see a problem when running CheckToursDBTest, where we end up in a kind
of deadlock situation. There are two threads, one daemon thread (D) updating
statistics, and one user thread (U) updating a table with some triggers.
Depending on timing, the following may happen:
D: takes S-locks on some rows in SYSDEPENDS for invalidation
U: compiles trigger/statement, enters DependencyManager.clearDependencies()
and grabs the monitor 'this'.
D: needs to enter DM.clearDependencies(), but U already has the monitor
'this' (BLOCKED)
U: needs to get X-locks on the rows already locked by D in SYSDEPENDS (TIMES
OUT)
D: after U is killed due to a lock timeout, D can continue and successfully
complete the invalidation
I have not yet figured out how/if this issue can be resolved.
Also, IndexStatisticsDaemon has to be moved to a different package, or at least
a new interface has to be introduced if the DataDictionary is used to access
the daemon. Any opinions on where to place and how to access the daemon?
I'm asking for review, particularly of the code in IndexStatisticsDaemon. The
changes in impl/sql would also benefit from review from someone who knows more
about the dynamics here.
When I run suites.All I see from zero to three failures on my machine. I've
also seen some failures in derbyall earlier, but I haven't run it with my
latest changes (will do).
Patch ready for review.
> Continue investigation of automatic creation/update of index statistics
> -----------------------------------------------------------------------
>
> Key: DERBY-4771
> URL: https://issues.apache.org/jira/browse/DERBY-4771
> Project: Derby
> Issue Type: Task
> Reporter: Kristian Waagan
> Assignee: Kristian Waagan
> Attachments: derby-4771-1a-prototype_code_dump.diff,
> derby-4771-1a-prototype_code_dump.stat,
> derby-4771-1b-prototype_code_dump.diff,
> derby-4771-2a-prototype_lcc_code_dump.diff,
> derby-4771-2b-prototype_lcc_code_dump.diff,
> derby-4771-2c-prototype_lcc_code_dump.diff, derby.log, error-stacktrace.out,
> rjall.out, rjall.out, rjall.rar, rjone.out
>
>
> Work was started to improve Derby's handling of index statistics. This issue
> tracks further discussion and work for this task.
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