SOLR-10754: Add hist Stream Evaluator

solr/core/src/java/org/apache/solr/handler/StreamHandler.java

@@ -191,6 +191,7 @@ public class StreamHandler extends RequestHandlerBase implements SolrCoreAware,
       .withFunctionName("finddelay", FindDelayEvaluator.class)
       .withFunctionName("sequence", SequenceEvaluator.class)
       .withFunctionName("array", ArrayEvaluator.class)
+      .withFunctionName("hist", HistogramEvaluator.class)
 
       // metrics
          .withFunctionName("min", MinMetric.class)

solr/solrj/src/java/org/apache/solr/client/solrj/io/eval/HistogramEvaluator.java

@@ -0,0 +1,98 @@
+/*
+ * 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.solr.client.solrj.io.eval;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.math3.random.EmpiricalDistribution;
+import org.apache.commons.math3.stat.descriptive.SummaryStatistics;
+import org.apache.solr.client.solrj.io.Tuple;
+import org.apache.solr.client.solrj.io.stream.expr.Explanation;
+import org.apache.solr.client.solrj.io.stream.expr.Explanation.ExpressionType;
+import org.apache.solr.client.solrj.io.stream.expr.Expressible;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpressionParameter;
+import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
+
+public class HistogramEvaluator extends ComplexEvaluator implements Expressible {
+
+  private static final long serialVersionUID = 1;
+
+  public HistogramEvaluator(StreamExpression expression, StreamFactory factory) throws IOException {
+    super(expression, factory);
+  }
+
+  public List<Map> evaluate(Tuple tuple) throws IOException {
+
+    StreamEvaluator colEval1 = subEvaluators.get(0);
+
+    List<Number> numbers1 = (List<Number>)colEval1.evaluate(tuple);
+    double[] column1 = new double[numbers1.size()];
+
+    for(int i=0; i<numbers1.size(); i++) {
+      column1[i] = numbers1.get(i).doubleValue();
+    }
+
+    int bins = 10;
+    if(subEvaluators.size() == 2) {
+      StreamEvaluator binsEval = subEvaluators.get(1);
+      Number binsNum = (Number) binsEval.evaluate(tuple);
+      bins = binsNum.intValue();
+    }
+
+    EmpiricalDistribution empiricalDistribution = new EmpiricalDistribution(bins);
+    empiricalDistribution.load(column1);
+
+    List<Map> binList = new ArrayList();
+
+    List<SummaryStatistics> summaries = empiricalDistribution.getBinStats();
+    for(SummaryStatistics statisticalSummary : summaries) {
+      Map map = new HashMap();
+      map.put("max", statisticalSummary.getMax());
+      map.put("mean", statisticalSummary.getMean());
+      map.put("min", statisticalSummary.getMin());
+      map.put("stdev", statisticalSummary.getStandardDeviation());
+      map.put("sum", statisticalSummary.getSum());
+      map.put("N", statisticalSummary.getN());
+      map.put("var", statisticalSummary.getVariance());
+      binList.add(map);
+    }
+
+    return binList;
+  }
+
+
+
+  @Override
+  public StreamExpressionParameter toExpression(StreamFactory factory) throws IOException {
+    StreamExpression expression = new StreamExpression(factory.getFunctionName(getClass()));
+    return expression;
+  }
+
+  @Override
+  public Explanation toExplanation(StreamFactory factory) throws IOException {
+    return new Explanation(nodeId.toString())
+        .withExpressionType(ExpressionType.EVALUATOR)
+        .withFunctionName(factory.getFunctionName(getClass()))
+        .withImplementingClass(getClass().getName())
+        .withExpression(toExpression(factory).toString());
+  }
+}

solr/solrj/src/test/org/apache/solr/client/solrj/io/stream/StreamExpressionTest.java

@@ -5227,6 +5227,53 @@ public class StreamExpressionTest extends SolrCloudTestCase {
     }
   }
 
+  @Test
+  public void testHist() throws Exception {
+    String expr = "hist(sequence(100, 0, 1), 10)";
+    ModifiableSolrParams paramsLoc = new ModifiableSolrParams();
+    paramsLoc.set("expr", expr);
+    paramsLoc.set("qt", "/stream");
+
+    String url = cluster.getJettySolrRunners().get(0).getBaseUrl().toString()+"/"+COLLECTIONORALIAS;
+    TupleStream solrStream = new SolrStream(url, paramsLoc);
+
+    StreamContext context = new StreamContext();
+    solrStream.setStreamContext(context);
+    List<Tuple> tuples = getTuples(solrStream);
+    assertTrue(tuples.size() == 1);
+    List<Map> hist = (List<Map>)tuples.get(0).get("return-value");
+    assertTrue(hist.size() == 10);
+    for(int i=0; i<hist.size(); i++) {
+      Map stats = hist.get(i);
+      assertTrue(((Number)stats.get("N")).intValue() == 10);
+      assertTrue(((Number)stats.get("min")).intValue() == 10*i);
+      assertTrue(((Number)stats.get("var")).doubleValue() == 9.166666666666666);
+      assertTrue(((Number)stats.get("stdev")).doubleValue() == 3.0276503540974917);
+    }
+
+    expr = "hist(sequence(100, 0, 1), 5)";
+    paramsLoc = new ModifiableSolrParams();
+    paramsLoc.set("expr", expr);
+    paramsLoc.set("qt", "/stream");
+
+    solrStream = new SolrStream(url, paramsLoc);
+    solrStream.setStreamContext(context);
+    tuples = getTuples(solrStream);
+    assertTrue(tuples.size() == 1);
+    hist = (List<Map>)tuples.get(0).get("return-value");
+    assertTrue(hist.size() == 5);
+    for(int i=0; i<hist.size(); i++) {
+      Map stats = hist.get(i);
+      assertTrue(((Number)stats.get("N")).intValue() == 20);
+      assertTrue(((Number)stats.get("min")).intValue() == 20*i);
+      assertTrue(((Number)stats.get("var")).doubleValue() == 35);
+      assertTrue(((Number)stats.get("stdev")).doubleValue() == 5.916079783099616);
+    }
+  }
+
+
+
+
 
 
   @Test
@@ -5747,7 +5794,7 @@ public class StreamExpressionTest extends SolrCloudTestCase {
     solrStream.setStreamContext(context);
     List<Tuple> tuples = getTuples(solrStream);
     assertTrue(tuples.size() == 1);
-    List<Number> out = (List<Number>)tuples.get(0).get("out");
+    List<Number> out = (List<Number>)tuples.get(0).get("return-value");
     assertTrue(out.size() == 6);
     assertTrue(out.get(0).intValue() == 1);
     assertTrue(out.get(1).intValue() == 2);
@@ -5764,7 +5811,7 @@ public class StreamExpressionTest extends SolrCloudTestCase {
     solrStream.setStreamContext(context);
     tuples = getTuples(solrStream);
     assertTrue(tuples.size() == 1);
-    out = (List<Number>)tuples.get(0).get("out");
+    out = (List<Number>)tuples.get(0).get("return-value");
     assertTrue(out.size() == 6);
     assertTrue(out.get(0).doubleValue() == 1.122D);
     assertTrue(out.get(1).doubleValue() == 2.222D);