SOLR-11567: Add triangularDistribution Stream Evaluator

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

@@ -271,6 +271,7 @@ public class StreamHandler extends RequestHandlerBase implements SolrCoreAware,
         .withFunctionName("matrix", MatrixEvaluator.class)
         .withFunctionName("transpose", TransposeEvaluator.class)
         .withFunctionName("unit", UnitEvaluator.class)
+        .withFunctionName("triangularDistribution", TriangularDistributionEvaluator.class)
 
         // Boolean Stream Evaluators
 

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

@@ -0,0 +1,46 @@
+/*
+ * 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 org.apache.commons.math3.distribution.TriangularDistribution;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
+import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
+
+public class TriangularDistributionEvaluator extends RecursiveNumericEvaluator implements ManyValueWorker {
+
+  private static final long serialVersionUID = 1;
+
+  public TriangularDistributionEvaluator(StreamExpression expression, StreamFactory factory) throws IOException {
+    super(expression, factory);
+  }
+
+  @Override
+  public Object doWork(Object... values) throws IOException {
+
+    if (values.length != 3) {
+      throw new IOException("Triangular distribution requires three numeric parameters low, mode, high");
+    }
+
+    double low = ((Number) values[0]).doubleValue();
+    double mode = ((Number) values[1]).doubleValue();
+    double high = ((Number) values[2]).doubleValue();
+
+    return new TriangularDistribution(low, mode, high);
+  }
+}

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

@@ -7025,6 +7025,40 @@ public class StreamExpressionTest extends SolrCloudTestCase {
 
   }
 
+  @Test
+  public void testTriangularDistribution() throws Exception {
+    String cexpr = "let(echo=true, " +
+        "a=describe(sample(triangularDistribution(10, 15, 30),10000)), " +
+        "b=describe(sample(triangularDistribution(10, 25, 30),10000)), " +
+        ")";
+
+    ModifiableSolrParams paramsLoc = new ModifiableSolrParams();
+    paramsLoc.set("expr", cexpr);
+    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);
+    Map a = (Map)tuples.get(0).get("a");
+    Map b = (Map)tuples.get(0).get("b");
+
+    Number sa = (Number)a.get("skewness");
+    Number sb = (Number)b.get("skewness");
+
+    Number mina = (Number)a.get("min");
+    Number maxa = (Number)a.get("max");
+
+    assertTrue(sa.doubleValue() > 0);
+    assertTrue(sb.doubleValue() < 0);
+    assertEquals(mina.doubleValue(), 10, .5);
+    assertEquals(maxa.doubleValue(), 30, .5);
+  }
+
+
+
+
   @Test
   public void testMean() throws Exception {
     String cexpr = "mean(array(1,2,3,4,5))";