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From DaveBirdsall <>
Subject [GitHub] incubator-trafodion pull request #766: [TRAFODION-2282][TRAFODION-882] New s...
Date Wed, 19 Oct 2016 16:52:27 GMT
GitHub user DaveBirdsall opened a pull request:

    [TRAFODION-2282][TRAFODION-882] New scheme to invalidate histogram cache

    This set of code changes leverages the query invalidation and security key invalidation
infrastructure to invalidate the histogram cache. The design is as follows:
    1.	At UPDATE STATISTICS time, after statistics have been written, a new stats invalidation
key is generated. The key contains the table UID of the table whose stats have been updated.
    2.	RMS propagates this key to all compilers in the cluster. Note that the master executors
need not know, as changing histograms does not invalidate query plans. (Hence SscpNewIncomingConnectionStream::processSecInvReq
ignores stats invalidation keys.)
    3.	The compiler main, when checking for invalidation keys it has not seen before, processes
the new stats invalidation keys. It removes from the HistogramCache any HistogramCacheEntry
that has the same table UID.
    4.	Fail safe logic to invalidate the entire histogram cache was added in the case that
the compiler has been idle so long that it may have missed seeing a stats invalidation key.
    Older code in HistogramCache::getHistograms (optimizer/NATable.cpp) that used a refresh
interval timing scheme to invalidate cache entries has been completely removed. As part of
this cleanup, two CQDs are no longer needed and are removed. Stubbed routines in ustats/hs_read.cpp
have been removed. Too, it was noticed that the modified time stamp was stubbed (and cannot
be un-stubbed), and so that was removed. Note that the redefinition time stamp is also stubbed
but it is so pervasive in so many data structures I chose to leave it alone for now.
    Several regression test expected files have been updated, as UPDATE STATISTICS now takes
effect immediately in a session resulting in plan changes and related data.

You can merge this pull request into a Git repository by running:

    $ git pull Trafodion2282

Alternatively you can review and apply these changes as the patch at:

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #766
commit 9a3cf2e53af6d9df7c8ec03665f5da5a0ebf8ab0
Author: Dave Birdsall <>
Date:   2016-10-19T16:49:51Z

    [TRAFODION-2282][TRAFODION-882] New scheme to invalidate histogram cache


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