[GitHub] [incubator-pinot] siddharthteotia commented on a change in pull request #6285: Improve performance for distinct queries

[GitBox <gi...@apache.org>]

siddharthteotia commented on a change in pull request #6285:
URL: https://github.com/apache/incubator-pinot/pull/6285#discussion_r533659152



##########
File path: pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/function/DistinctAggregationFunction.java
##########
@@ -18,31 +18,25 @@
  */
 package org.apache.pinot.core.query.aggregation.function;
 
-import com.google.common.base.Preconditions;
-import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import javax.annotation.Nullable;
 import org.apache.pinot.common.function.AggregationFunctionType;
-import org.apache.pinot.common.utils.DataSchema;
 import org.apache.pinot.common.utils.DataSchema.ColumnDataType;
 import org.apache.pinot.core.common.BlockValSet;
-import org.apache.pinot.core.common.RowBasedBlockValueFetcher;
-import org.apache.pinot.core.data.table.Record;
 import org.apache.pinot.core.query.aggregation.AggregationResultHolder;
-import org.apache.pinot.core.query.aggregation.ObjectAggregationResultHolder;
-import org.apache.pinot.core.query.aggregation.function.customobject.DistinctTable;
 import org.apache.pinot.core.query.aggregation.groupby.GroupByResultHolder;
 import org.apache.pinot.core.query.request.context.ExpressionContext;
 import org.apache.pinot.core.query.request.context.OrderByExpressionContext;
 
 
 /**
- * The DISTINCT clause in SQL is executed as the DISTINCT aggregation function.
- * TODO: Support group-by
+ * The DISTINCT clause in SQL is represented as the DISTINCT aggregation function. Currently it is only used to wrap the
+ * information for the distinct queries.
+ * TODO: Use a separate way to represent DISTINCT instead of aggregation.
  */
 @SuppressWarnings("rawtypes")
-public class DistinctAggregationFunction implements AggregationFunction<DistinctTable, Comparable> {
+public class DistinctAggregationFunction implements AggregationFunction<Object, Comparable> {

Review comment:
       DISTINCT is supported in PinotQuery as a function. The CalciteSqlParser compiles Distinct specifically as a function expression.
   
   ```
   private static List<Expression> convertDistinctSelectList(SqlNodeList selectList) {
       List<Expression> selectExpr = new ArrayList<>();
       selectExpr.add(convertDistinctAndSelectListToFunctionExpression(selectList));
       return selectExpr;
     }
   ```
   
   




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