MONDRIAN: Prevents Mondrian from doing a raw-data rollup using the di…

…stinct-count aggregator. We can't rollup from raw data for distinct count measures because this would only sum up the distinct counts and gives invalid results.

[git-p4: depot-paths = "//open/mondrian/": change = 14928]

src/main/mondrian/rolap/FastBatchingCellReader.java

@@ -598,7 +598,15 @@ private void recordCellRequest2(final CellRequest request) {
         // with the same target dimensionality. It is quite likely that the
         // other rollup will satisfy this request, and it's complicated to be
         // 100% sure. If we're wrong, we'll be back.
-        if (measure.getAggregator().getRollup().supportsFastAggregates(
+
+        // Also make sure that we don't try to rollup a measure which
+        // doesn't support rollup from raw data, like a distinct count
+        // for example. Both the measure's aggregator and its rollup
+        // aggregator must support raw data aggregation. We call
+        // Aggregator.supportsFastAggregates() to verify.
+        if (measure.getAggregator().supportsFastAggregates(
+                measure.getDatatype())
+            && measure.getAggregator().getRollup().supportsFastAggregates(
                 measure.getDatatype())
             && !rollupBitmaps.contains(request.getConstrainedColumnsBitKey()))
         {

src/main/mondrian/rolap/RolapAggregator.java

@@ -214,6 +214,14 @@ public Object aggregate(
             public String getExpression(String operand) {
                 return "count(distinct " + operand + ")";
             }
+
+            public boolean supportsFastAggregates(
+                mondrian.spi.Dialect.Datatype dataType)
+            {
+                // We can't rollup using the raw data, because this is
+                // a distinct-count operation.
+                return false;
+            };
         };
 
     /**