Github user DaveBirdsall commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/195#discussion_r46173600
--- Diff: core/sql/optimizer/ScanOptimizer.cpp ---
@@ -374,8 +399,21 @@ static NABoolean checkMDAMadditionalRestriction(const
ColumnOrderList& keyPredsB
}
}
- if(presentKeyColumns > noOfmissingKeyColumns) return TRUE;
- return FALSE;
+ switch ( strategy ) {
+ case MAJORITY_WITH_PREDICATES:
+ return (presentKeyColumns > noOfmissingKeyColumns);
--- End diff --
I am not sure I see the point of this strategy. Suppose I have a 6 column
key and a query with predicates on 4 columns. It makes a huge difference
whether the predicates are on the leading columns (better) vs. the trailing
columns (worse). This heuristic does not take the column order into account.
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