GitHub user DaveBirdsall opened a pull request:
https://github.com/apache/incubator-trafodion/pull/1316
[TRAFODION-2822] Make [first n] views non-updatable; prevent bad MERGE plans
This pull request contains two changes:
1. Views defined using [first n] or [any n] are now marked as not updatable
and not insertable. So, when a MERGE statement is attempted on a new view of
this type, we will get a compile time error that the view is not insertable or
updatable (instead of getting an incorrect result).
2. MERGE statements that have a WHEN NOT MATCHED INSERT action are
prevented from undergoing a tuple substitution transformation (that is, the
TSJRule and TSJFlowRule will not fire on a merge node possessing a WHEN NOT
MATCHED INSERT action). This is necessary because the run-time implementation
of insert actions takes place in the merge node itself; that is, scanning has
to happen in the merge node. These two rules would take the scanning out of the
merge node into a separate scan node.
Note: Existing [first n] / [any n] views remain marked as updatable and
insertable. (These attributes are calculated at CREATE VIEW time and stored in
the metadata.) The second change above will cause MERGE statements having WHEN
NOT MATCHED INSERT actions to fail at compile time against such views with an
error 2235 (Optimizer could not produce a plan for the statement). While this
is a non-obvious error from a user perspective it is far better than allowing
execution and getting an incorrect result.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/DaveBirdsall/incubator-trafodion Trafodion2822
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-trafodion/pull/1316.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #1316
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