Github user selvaganesang commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/380#discussion_r56233621
--- Diff: core/sql/optimizer/BindRelExpr.cpp ---
@@ -10171,17 +10164,26 @@ matched clause of merge). If the upsert caused a
row to be updated in the
base table then the old version of the row will have to be deleted from
indexes, and a new version inserted. Upsert is being transformed to merge
so that we can delete the old version of an updated row from the index.
+
+Upsert is also converted into merge when there are omitted cols with
default values and
+TRAF_UPSERT_WITH_INSERT_DEFAULT_SEMANTICS is set to OFF in case of
aligned format table or
+omitted current timestamp cols in case of non-aligned row format
--- End diff --
For upsert, in case of non-aligned format, if any column other than the
columns with default current is omitted, the default value is resolved at the
time of select. If the current default column is omitted it will be always
changed to merge. User can't force a different behavior for non-aligned format
in this specific case. Rationale here: If we allow user to control it, then all
omitted default columns should always be populated at the time of upsert for
the merge to work correctly.
For non-aligned format, user control it using the above cqd. Default
behavior is change it to merge if the default columns are omitted in upsert.
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