DATAMONGO-1552 - Add $bucketAuto aggregation stage.

Original Pull Request: #426

Author: mp911de

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Aggregation.java

@@ -419,7 +419,7 @@ public static OutOperation out(String outCollectionName) {
 	}
 
 	/**
-	 * Creates a new {@link BucketOperation} using given {@literal groupByField}.
+	 * Creates a new {@link BucketOperation} given {@literal groupByField}.
 	 *
 	 * @param groupByField must not be {@literal null} or empty.
 	 * @return
@@ -429,7 +429,7 @@ public static BucketOperation bucket(String groupByField) {
 	}
 
 	/**
-	 * Creates a new {@link BucketOperation} using given {@link AggregationExpression group-by expression}.
+	 * Creates a new {@link BucketOperation} given {@link AggregationExpression group-by expression}.
 	 *
 	 * @param groupByExpression must not be {@literal null}.
 	 * @return
@@ -438,6 +438,28 @@ public static BucketOperation bucket(AggregationExpression groupByExpression) {
 		return new BucketOperation(groupByExpression);
 	}
 
+	/**
+	 * Creates a new {@link BucketAutoOperation} given {@literal groupByField}.
+	 *
+	 * @param groupByField must not be {@literal null} or empty.
+	 * @param buckets number of buckets, must be a positive integer.
+	 * @return
+	 */
+	public static BucketAutoOperation bucketAuto(String groupByField, int buckets) {
+		return new BucketAutoOperation(field(groupByField), buckets);
+	}
+
+	/**
+	 * Creates a new {@link BucketAutoOperation} given {@link AggregationExpression group-by expression}.
+	 *
+	 * @param groupByExpression must not be {@literal null}.
+	 * @param buckets number of buckets, must be a positive integer.
+	 * @return
+	 */
+	public static BucketAutoOperation bucketAuto(AggregationExpression groupByExpression, int buckets) {
+		return new BucketAutoOperation(groupByExpression, buckets);
+	}
+
 	/**
 	 * Creates a new {@link LookupOperation}.
 	 *

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperation.java

@@ -0,0 +1,273 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed 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.springframework.data.mongodb.core.aggregation;
+
+import org.springframework.data.mongodb.core.aggregation.BucketAutoOperation.BucketAutoOperationOutputBuilder;
+import org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder;
+import org.springframework.util.Assert;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * Encapsulates the aggregation framework {@code $bucketAuto}-operation.
+ * <p>
+ * Bucket stage is typically used with {@link Aggregation} and {@code $facet}. Categorizes incoming documents into a
+ * specific number of groups, called buckets, based on a specified expression. Bucket boundaries are automatically
+ * determined in an attempt to evenly distribute the documents into the specified number of buckets.
+ * <p>
+ * We recommend to use the static factory method {@link Aggregation#bucketAuto(String, int)} instead of creating instances of
+ * this class directly.
+ *
+ * @see http://docs.mongodb.org/manual/reference/aggregation/bucketAuto/
+ * @see BucketOperationSupport
+ * @author Mark Paluch
+ * @since 1.10
+ */
+public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperation, BucketAutoOperationOutputBuilder>
+		implements FieldsExposingAggregationOperation {
+
+	private final int buckets;
+	private final String granularity;
+
+	/**
+	 * Creates a new {@link BucketAutoOperation} given a {@link Field group-by field}.
+	 *
+	 * @param groupByField must not be {@literal null}.
+	 * @param buckets number of buckets, must be a positive integer.
+	 */
+	public BucketAutoOperation(Field groupByField, int buckets) {
+
+		super(groupByField);
+
+		Assert.isTrue(buckets > 0, "Number of buckets must be greater 0!");
+
+		this.buckets = buckets;
+		this.granularity = null;
+	}
+
+	/**
+	 * Creates a new {@link BucketAutoOperation} given a {@link AggregationExpression group-by expression}.
+	 *
+	 * @param groupByExpression must not be {@literal null}.
+	 * @param buckets number of buckets, must be a positive integer.
+	 */
+	public BucketAutoOperation(AggregationExpression groupByExpression, int buckets) {
+
+		super(groupByExpression);
+
+		Assert.isTrue(buckets > 0, "Number of buckets must be greater 0!");
+
+		this.buckets = buckets;
+		this.granularity = null;
+	}
+
+	private BucketAutoOperation(BucketAutoOperation bucketOperation, Outputs outputs) {
+
+		super(bucketOperation, outputs);
+
+		this.buckets = bucketOperation.buckets;
+		this.granularity = bucketOperation.granularity;
+	}
+
+	private BucketAutoOperation(BucketAutoOperation bucketOperation, int buckets, String granularity) {
+
+		super(bucketOperation);
+
+		this.buckets = buckets;
+		this.granularity = granularity;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+
+		DBObject options = new BasicDBObject();
+
+		options.put("buckets", buckets);
+
+		if (granularity != null) {
+			options.put("granularity", granularity);
+		}
+
+		options.putAll(super.toDBObject(context));
+
+		return new BasicDBObject("$bucketAuto", options);
+	}
+
+	/**
+	 * Configures a number of bucket {@literal buckets} and return a new {@link BucketAutoOperation}.
+	 *
+	 * @param buckets must be a positive number.
+	 * @return
+	 */
+	public BucketAutoOperation withBuckets(int buckets) {
+
+		Assert.isTrue(buckets > 0, "Number of buckets must be greater 0!");
+		return new BucketAutoOperation(this, buckets, granularity);
+	}
+
+	/**
+	 * Configures {@literal granularity} that specifies the preferred number series to use to ensure that the calculated
+	 * boundary edges end on preferred round numbers or their powers of 10 and return a new {@link BucketAutoOperation}.
+	 *
+	 * @param granularity must not be {@literal null}.
+	 * @return
+	 */
+	public BucketAutoOperation withGranularity(Granularity granularity) {
+
+		Assert.notNull(granularity, "Granularity must not be null!");
+
+		return new BucketAutoOperation(this, buckets, granularity.toMongoGranularity());
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#newBucketOperation(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.Outputs)
+	 */
+	@Override
+	protected BucketAutoOperation newBucketOperation(Outputs outputs) {
+		return new BucketAutoOperation(this, outputs);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutputExpression(java.lang.String, java.lang.Object[])
+	 */
+	@Override
+	public ExpressionBucketAutoOperationBuilder andOutputExpression(String expression, Object... params) {
+		return new ExpressionBucketAutoOperationBuilder(expression, this, params);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutput(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+	 */
+	@Override
+	public BucketAutoOperationOutputBuilder andOutput(AggregationExpression expression) {
+		return new BucketAutoOperationOutputBuilder(expression, this);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutput(java.lang.String)
+	 */
+	@Override
+	public BucketAutoOperationOutputBuilder andOutput(String fieldName) {
+		return new BucketAutoOperationOutputBuilder(Fields.field(fieldName), this);
+	}
+
+	/**
+	 * {@link OutputBuilder} implementation for {@link BucketAutoOperation}.
+	 */
+	public static class BucketAutoOperationOutputBuilder
+			extends OutputBuilder<BucketAutoOperationOutputBuilder, BucketAutoOperation> {
+
+		/**
+		 * Creates a new {@link BucketAutoOperationOutputBuilder} fot the given value and {@link BucketAutoOperation}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 */
+		protected BucketAutoOperationOutputBuilder(Object value, BucketAutoOperation operation) {
+			super(value, operation);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder#apply(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OperationOutput)
+		 */
+		@Override
+		protected BucketAutoOperationOutputBuilder apply(OperationOutput operationOutput) {
+			return new BucketAutoOperationOutputBuilder(operationOutput, this.operation);
+		}
+	}
+
+	/**
+	 * {@link ExpressionBucketOperationBuilderSupport} implementation for {@link BucketAutoOperation} using SpEL
+	 * expression based {@link Output}.
+	 * 
+	 * @author Mark Paluch
+	 */
+	public static class ExpressionBucketAutoOperationBuilder
+			extends ExpressionBucketOperationBuilderSupport<BucketAutoOperationOutputBuilder, BucketAutoOperation> {
+
+		/**
+		 * Creates a new {@link ExpressionBucketAutoOperationBuilder} for the given value, {@link BucketAutoOperation} and
+		 * parameters.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 * @param parameters
+		 */
+		protected ExpressionBucketAutoOperationBuilder(String expression, BucketAutoOperation operation,
+				Object[] parameters) {
+			super(expression, operation, parameters);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder#apply(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OperationOutput)
+		 */
+		@Override
+		protected BucketAutoOperationOutputBuilder apply(OperationOutput operationOutput) {
+			return new BucketAutoOperationOutputBuilder(operationOutput, this.operation);
+		}
+	}
+
+	/**
+	 * @author Mark Paluch
+	 */
+	public static interface Granularity {
+
+		/**
+		 * @return a String that represents a MongoDB granularity to be used with {@link BucketAutoOperation}.
+		 */
+		String toMongoGranularity();
+	}
+
+	/**
+	 * Supported MongoDB granularities.
+	 *
+	 * @see https://en.wikipedia.org/wiki/Preferred_number
+	 * @see https://docs.mongodb.com/manual/reference/operator/aggregation/bucketAuto/#granularity
+	 * @author Mark Paluch
+	 */
+	public enum Granularities implements Granularity {
+
+		R5, R10, R20, R40, R80, //
+
+		SERIES_1_2_5("1-2-5"), //
+
+		E6, E12, E24, E48, E96, E192, //
+
+		POWERSOF2;
+
+		final String granularity;
+
+		Granularities() {
+			this.granularity = name();
+		}
+
+		Granularities(String granularity) {
+			this.granularity = granularity;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.GranularitytoMongoGranularity()
+		 */
+		@Override
+		public String toMongoGranularity() {
+			return granularity;
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperationSupport.java

@@ -222,7 +222,7 @@ public abstract static class OutputBuilder<B extends OutputBuilder<B, T>, T exte
 		 * @param value must not be {@literal null}.
 		 * @param operation must not be {@literal null}.
 		 */
-		public OutputBuilder(Object value, T operation) {
+		protected OutputBuilder(Object value, T operation) {
 
 			Assert.notNull(value, "Value must not be null or empty!");
 			Assert.notNull(operation, "ProjectionOperation must not be null!");
@@ -433,6 +433,11 @@ private Outputs(Collection<Output> current, Output output) {
 		 */
 		protected ExposedFields asExposedFields() {
 
+			// The count field is included by default when the output is not specified.
+			if (isEmpty()) {
+				return ExposedFields.from(new ExposedField("count", true));
+			}
+
 			ExposedFields fields = ExposedFields.from();
 
 			for (Output output : outputs) {

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/AggregationTests.java

@@ -61,7 +61,9 @@
 import org.springframework.data.mongodb.core.aggregation.AggregationExpressions.ConditionalOperators;
 import org.springframework.data.mongodb.core.aggregation.AggregationExpressions.Let;
 import org.springframework.data.mongodb.core.aggregation.AggregationExpressions.Let.ExpressionVariable;
+import org.springframework.data.mongodb.core.aggregation.AggregationExpressions.Multiply;
 import org.springframework.data.mongodb.core.aggregation.AggregationTests.CarDescriptor.Entry;
+import org.springframework.data.mongodb.core.aggregation.BucketAutoOperation.Granularities;
 import org.springframework.data.mongodb.core.index.GeospatialIndex;
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.data.mongodb.core.query.Criteria;
@@ -1708,6 +1710,43 @@ public void bucketShouldCollectDocumentsIntoABucket() {
 		assertThat((Double) bound100.get("sum"), is(closeTo(3672.9, 0.1)));
 	}
 
+	/**
+	 * @see DATAMONGO-1552
+	 */
+	@Test
+	public void bucketAutoShouldCollectDocumentsIntoABucket() {
+
+		assumeTrue(mongoVersion.isGreaterThanOrEqualTo(THREE_DOT_FOUR));
+
+		Art a1 = Art.builder().id(1).title("The Pillars of Society").artist("Grosz").year(1926).price(199.99).build();
+		Art a2 = Art.builder().id(2).title("Melancholy III").artist("Munch").year(1902).price(280.00).build();
+		Art a3 = Art.builder().id(3).title("Dancer").artist("Miro").year(1925).price(76.04).build();
+		Art a4 = Art.builder().id(4).title("The Great Wave off Kanagawa").artist("Hokusai").price(167.30).build();
+
+		mongoTemplate.insert(Arrays.asList(a1, a2, a3, a4), Art.class);
+
+		TypedAggregation<Art> aggregation = newAggregation(Art.class, //
+				bucketAuto(Multiply.valueOf("price").multiplyBy(10), 3) //
+						.withGranularity(Granularities.E12) //
+						.andOutputCount().as("count") //
+						.andOutput("title").push().as("titles") //
+						.andOutputExpression("price * 10").sum().as("sum"));
+
+		AggregationResults<DBObject> result = mongoTemplate.aggregate(aggregation, DBObject.class);
+		assertThat(result.getMappedResults().size(), is(3));
+
+		// { "min" : 680.0 , "max" : 820.0 , "count" : 1 , "titles" : [ "Dancer"] , "sum" : 760.4000000000001}
+		DBObject bound0 = result.getMappedResults().get(0);
+		assertThat(bound0, isBsonObject().containing("count", 1).containing("titles.[0]", "Dancer").containing("min", 680.0)
+				.containing("max"));
+
+		// { "min" : 820.0 , "max" : 1800.0 , "count" : 1 , "titles" : [ "The Great Wave off Kanagawa"] , "sum" : 1673.0}
+		DBObject bound1 = result.getMappedResults().get(1);
+		assertThat(bound1, isBsonObject().containing("count", 1).containing("min", 820.0));
+		assertThat((List<String>) bound1.get("titles"), hasItems("The Great Wave off Kanagawa"));
+		assertThat((Double) bound1.get("sum"), is(closeTo(1673.0, 0.1)));
+	}
+
 	private void createUsersWithReferencedPersons() {
 
 		mongoTemplate.dropCollection(User.class);