[GitHub] andresgomezfrr commented on a change in pull request #5789: Add stringLast and stringFirst aggregators extension

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

andresgomezfrr commented on a change in pull request #5789: Add stringLast and stringFirst aggregators extension
URL: https://github.com/apache/incubator-druid/pull/5789#discussion_r205681438
 
 

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 File path: processing/src/main/java/io/druid/query/aggregation/first/StringFirstBufferAggregator.java
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+/*
+ * Licensed to Metamarkets Group Inc. (Metamarkets) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Metamarkets 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 io.druid.query.aggregation.first;
+
+import io.druid.java.util.common.StringUtils;
+import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.aggregation.SerializablePairLongString;
+import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
+import io.druid.segment.BaseLongColumnValueSelector;
+import io.druid.segment.BaseObjectColumnValueSelector;
+
+import java.nio.ByteBuffer;
+
+// TODO: Unit Test
+public class StringFirstBufferAggregator implements BufferAggregator
+{
+  private final BaseLongColumnValueSelector timeSelector;
+  private final BaseObjectColumnValueSelector valueSelector;
+  private final int maxStringBytes;
+
+  public StringFirstBufferAggregator(
+      BaseLongColumnValueSelector timeSelector,
+      BaseObjectColumnValueSelector valueSelector,
+      int maxStringBytes
+  )
+  {
+    this.timeSelector = timeSelector;
+    this.valueSelector = valueSelector;
+    this.maxStringBytes = maxStringBytes;
+  }
+
+  @Override
+  public void init(ByteBuffer buf, int position)
+  {
+    buf.putLong(position, Long.MAX_VALUE);
+    buf.putInt(position + Long.BYTES, 0);
+  }
+
+  @Override
+  public void aggregate(ByteBuffer buf, int position)
+  {
+    ByteBuffer mutationBuffer = buf.duplicate();
+    mutationBuffer.position(position);
+
+    Object value = valueSelector.getObject();
+
+    long time = Long.MAX_VALUE;
+    String firstString = null;
+
+    if (value instanceof SerializablePairLongString) {
+      SerializablePairLongString serializablePair = (SerializablePairLongString) value;
+      time = serializablePair.lhs;
+      firstString = serializablePair.rhs;
+    } else if (value instanceof String) {
+      time = timeSelector.getLong();
+      firstString = (String) value;
+    } else if (value != null) {
+      throw new IllegalStateException(
+          "Try to aggregate unsuported class type ["
+          + value.getClass().getName() +
+          "]. Supported class types: String or SerializablePairLongString"
+      );
+    }
+
+    long lastTime = mutationBuffer.getLong(position);
+    if (firstString != null && time < lastTime) {
 
 Review comment:
   @jihoonson Maybe we can add an aggregation option `filterNullValues` (by default: `false`). What do you think?

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