SOLR-10724: Add describe Stream Evaluator

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

@@ -183,6 +183,7 @@ public class StreamHandler extends RequestHandlerBase implements SolrCoreAware,
       .withFunctionName("copyOfRange", CopyOfRangeEvaluator.class)
       .withFunctionName("percentile", PercentileEvaluator.class)
       .withFunctionName("empiricalDistribution", EmpiricalDistributionEvaluator.class)
+      .withFunctionName("describe", DescribeEvaluator.class)
 
       // metrics
          .withFunctionName("min", MinMetric.class)

solr/solrj/src/java/org/apache/solr/client/solrj/io/stream/DescribeEvaluator.java

@@ -0,0 +1,92 @@
+/*
+ * 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.stream;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;
+import org.apache.solr.client.solrj.io.Tuple;
+import org.apache.solr.client.solrj.io.eval.ComplexEvaluator;
+import org.apache.solr.client.solrj.io.eval.StreamEvaluator;
+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 DescribeEvaluator extends ComplexEvaluator implements Expressible {
+
+  private static final long serialVersionUID = 1;
+
+  public DescribeEvaluator(StreamExpression expression, StreamFactory factory) throws IOException {
+    super(expression, factory);
+  }
+
+  public Tuple evaluate(Tuple tuple) throws IOException {
+
+    if(subEvaluators.size() != 1) {
+      throw new IOException("describe expects 1 column as a parameters");
+    }
+
+    StreamEvaluator colEval = subEvaluators.get(0);
+
+    List<Number> numbers = (List<Number>)colEval.evaluate(tuple);
+    DescriptiveStatistics descriptiveStatistics = new DescriptiveStatistics();
+
+    for(Number n : numbers) {
+      descriptiveStatistics.addValue(n.doubleValue());
+    }
+
+
+    Map map = new HashMap();
+
+    map.put("max", descriptiveStatistics.getMax());
+    map.put("mean", descriptiveStatistics.getMean());
+    map.put("min", descriptiveStatistics.getMin());
+    map.put("stdev", descriptiveStatistics.getStandardDeviation());
+    map.put("sum", descriptiveStatistics.getSum());
+    map.put("N", descriptiveStatistics.getN());
+    map.put("var", descriptiveStatistics.getVariance());
+    map.put("kurtosis", descriptiveStatistics.getKurtosis());
+    map.put("skewness", descriptiveStatistics.getSkewness());
+    map.put("popVar", descriptiveStatistics.getPopulationVariance());
+    map.put("geometricMean", descriptiveStatistics.getGeometricMean());
+    map.put("sumsq", descriptiveStatistics.getSumsq());
+
+    return new Tuple(map);
+  }
+
+
+  @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

@@ -5819,6 +5819,61 @@ public class StreamExpressionTest extends SolrCloudTestCase {
     assertTrue(prediction == 600.0D);
   }
 
+  @Test
+  public void testDescribe() throws Exception {
+    UpdateRequest updateRequest = new UpdateRequest();
+
+
+    updateRequest.add(id, "1", "price_f", "100.0", "col_s", "a", "order_i", "1");
+    updateRequest.add(id, "2", "price_f", "200.0", "col_s", "a", "order_i", "2");
+    updateRequest.add(id, "3", "price_f", "300.0", "col_s", "a", "order_i", "3");
+    updateRequest.add(id, "4", "price_f", "100.0", "col_s", "a", "order_i", "4");
+    updateRequest.add(id, "5", "price_f", "200.0", "col_s", "a", "order_i", "5");
+    updateRequest.add(id, "6", "price_f", "400.0", "col_s", "a", "order_i", "6");
+    updateRequest.add(id, "7", "price_f", "600.0", "col_s", "a", "order_i", "7");
+
+
+    updateRequest.commit(cluster.getSolrClient(), COLLECTIONORALIAS);
+
+    String expr1 = "search("+COLLECTIONORALIAS+", q=\"col_s:a\", fl=\"price_f, order_i\", sort=\"order_i asc\")";
+
+    String cexpr = "let(a="+expr1+", b=col(a, price_f),  tuple(stats=describe(b)))";
+
+    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);
+    Tuple tuple = tuples.get(0);
+    Map stats = (Map)tuple.get("stats");
+    Number min = (Number)stats.get("min");
+    Number max = (Number)stats.get("max");
+    Number mean = (Number)stats.get("mean");
+    Number stdev = (Number)stats.get("stdev");
+    Number popVar = (Number)stats.get("popVar");
+    Number skewness = (Number)stats.get("skewness");
+    Number kurtosis = (Number)stats.get("kurtosis");
+    Number var = (Number)stats.get("var");
+    Number geometricMean = (Number)stats.get("geometricMean");
+    Number N = (Number)stats.get("N");
+    assertEquals(min.doubleValue(), 100.0D, 0.0);
+    assertEquals(max.doubleValue(), 600.0D, 0.0);
+    assertEquals(N.doubleValue(), 7.0D, 0.0);
+    assertEquals(mean.doubleValue(), 271.42D, 0.5);
+    assertEquals(popVar.doubleValue(), 27755.10, 0.5);
+    assertEquals(kurtosis.doubleValue(), .70D, 0.5);
+    assertEquals(skewness.doubleValue(), 1.07D, 0.5);
+    assertEquals(var.doubleValue(), 32380.95D, 0.5);
+    assertEquals(geometricMean .doubleValue(), 224.56D, 0.5);
+    assertEquals(stdev .doubleValue(), 179.94D, 0.5);
+  }
+
 
   @Test
   public void testLength() throws Exception {