[GitHub] [incubator-druid] jon-wei commented on a change in pull request #8100: SQL support for t-digest based sketch aggregators

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jon-wei commented on a change in pull request #8100: SQL support for t-digest based sketch aggregators
URL: https://github.com/apache/incubator-druid/pull/8100#discussion_r309914605
 
 

 ##########
 File path: extensions-contrib/tdigestsketch/src/main/java/org/apache/druid/query/aggregation/tdigestsketch/sql/TDigestSketchQuantileSqlAggregator.java
 ##########
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.query.aggregation.tdigestsketch.sql;
+
+import com.google.common.collect.ImmutableList;
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.Project;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexLiteral;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.SqlAggFunction;
+import org.apache.calcite.sql.SqlFunctionCategory;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.type.OperandTypes;
+import org.apache.calcite.sql.type.ReturnTypes;
+import org.apache.calcite.sql.type.SqlTypeFamily;
+import org.apache.calcite.sql.type.SqlTypeName;
+import org.apache.druid.java.util.common.StringUtils;
+import org.apache.druid.query.aggregation.AggregatorFactory;
+import org.apache.druid.query.aggregation.post.FieldAccessPostAggregator;
+import org.apache.druid.query.aggregation.tdigestsketch.TDigestSketchAggregatorFactory;
+import org.apache.druid.query.aggregation.tdigestsketch.TDigestSketchToQuantilePostAggregator;
+import org.apache.druid.segment.VirtualColumn;
+import org.apache.druid.segment.virtual.ExpressionVirtualColumn;
+import org.apache.druid.sql.calcite.aggregation.Aggregation;
+import org.apache.druid.sql.calcite.aggregation.SqlAggregator;
+import org.apache.druid.sql.calcite.expression.DruidExpression;
+import org.apache.druid.sql.calcite.expression.Expressions;
+import org.apache.druid.sql.calcite.planner.PlannerContext;
+import org.apache.druid.sql.calcite.rel.VirtualColumnRegistry;
+import org.apache.druid.sql.calcite.table.RowSignature;
+
+import javax.annotation.Nullable;
+import java.util.ArrayList;
+import java.util.List;
+
+public class TDigestSketchQuantileSqlAggregator implements SqlAggregator
+{
+  private static final SqlAggFunction FUNCTION_INSTANCE = new TDigestSketchQuantileSqlAggFunction();
+  private static final String NAME = "TDIGEST_QUANTILE";
+
+  @Override
+  public SqlAggFunction calciteFunction()
+  {
+    return FUNCTION_INSTANCE;
+  }
+
+  @Nullable
+  @Override
+  public Aggregation toDruidAggregation(
+      final PlannerContext plannerContext,
+      final RowSignature rowSignature,
+      final VirtualColumnRegistry virtualColumnRegistry,
+      final RexBuilder rexBuilder,
+      final String name,
+      final AggregateCall aggregateCall,
+      final Project project,
+      final List<Aggregation> existingAggregations,
+      final boolean finalizeAggregations
+  )
+  {
+    // This is expected to be a tdigest sketch
+    final DruidExpression input = Expressions.toDruidExpression(
+        plannerContext,
+        rowSignature,
+        Expressions.fromFieldAccess(
+            rowSignature,
+            project,
+            aggregateCall.getArgList().get(0)
+        )
+    );
+    if (input == null) {
+      return null;
+    }
+
+    final AggregatorFactory aggregatorFactory;
+    final String histogramName = StringUtils.format("%s:agg", name);
+
+    // this is expected to be quantile fraction
+    final RexNode quantileArg = Expressions.fromFieldAccess(
+        rowSignature,
+        project,
+        aggregateCall.getArgList().get(1)
+    );
+
+    if (!quantileArg.isA(SqlKind.LITERAL)) {
+      // Quantile must be a literal in order to plan.
+      return null;
+    }
+
+    final double quantile = ((Number) RexLiteral.value(quantileArg)).floatValue();
+    Integer compression = null;
+    if (aggregateCall.getArgList().size() > 2) {
+      final RexNode compressionArg = Expressions.fromFieldAccess(
+          rowSignature,
+          project,
+          aggregateCall.getArgList().get(2)
+      );
+      compression = ((Number) RexLiteral.value(compressionArg)).intValue();
+    }
+
+    // Look for existing matching aggregatorFactory.
+    for (final Aggregation existing : existingAggregations) {
+      for (AggregatorFactory factory : existing.getAggregatorFactories()) {
+        if (factory instanceof TDigestSketchAggregatorFactory) {
+          final TDigestSketchAggregatorFactory theFactory = (TDigestSketchAggregatorFactory) factory;
+
+          // Check input for equivalence.
+          final boolean inputMatches;
+          final VirtualColumn virtualInput = existing.getVirtualColumns()
+                                                     .stream()
+                                                     .filter(
+                                                         virtualColumn ->
+                                                             virtualColumn.getOutputName()
+                                                                          .equals(theFactory.getFieldName())
+                                                     )
+                                                     .findFirst()
+                                                     .orElse(null);
+
+          if (virtualInput == null) {
+            inputMatches = input.isDirectColumnAccess()
+                           && input.getDirectColumn().equals(theFactory.getFieldName());
+          } else {
+            inputMatches = ((ExpressionVirtualColumn) virtualInput).getExpression()
+                                                                   .equals(input.getExpression());
+          }
+
+          if (inputMatches) {
 
 Review comment:
   Ah, it should just check compression

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