DATACOUCH-168 - Support and document all reduce functions

Detection whether or not reduce should be activated is now centralized. Triggers are:
  - using the count prefix instead of find in method name
  - setting reduce = true in the View annotation explicitly.

The reduce can thus be returning any kind of value (added an integration example with _stats), which is now properly documented.

src/main/java/org/springframework/data/couchbase/core/view/View.java

@@ -52,4 +52,6 @@ public @interface View {
    */
   String viewName() default "";
 
+  boolean reduce() default false;
+
 }

src/main/java/org/springframework/data/couchbase/repository/query/ViewBasedCouchbaseQuery.java

@@ -68,13 +68,14 @@ public class ViewBasedCouchbaseQuery implements RepositoryQuery {
   protected Object guessViewAndExecute() {
     String designDoc = designDocName(method);
     String methodName = method.getName();
-    boolean isReduce = methodName.startsWith("count");
+    boolean isExplicitReduce = method.hasViewAnnotation() && method.getViewAnnotation().reduce();
+    boolean isReduce = methodName.startsWith("count") || isExplicitReduce;
     String viewName = StringUtils.uncapitalize(methodName.replaceFirst("find|count", ""));
 
     ViewQuery simpleQuery = ViewQuery.from(designDoc, viewName)
         .stale(operations.getDefaultConsistency().viewConsistency());
     if (isReduce) {
-      simpleQuery.reduce(isReduce);
+      simpleQuery.reduce();
       return executeReduce(simpleQuery, designDoc, viewName);
     } else {
       return execute(simpleQuery);
@@ -94,15 +95,14 @@ public class ViewBasedCouchbaseQuery implements RepositoryQuery {
 
       //use a ViewQueryCreator to complete the base query
       ViewQueryCreator creator = new ViewQueryCreator(tree, new ParametersParameterAccessor(method.getParameters(), runtimeParams),
-          baseQuery, operations.getConverter());
-      ViewQuery query = creator.createQuery();
+          method.getViewAnnotation(), baseQuery, operations.getConverter());
+      ViewQueryCreator.DerivedViewQuery result = creator.createQuery();
 
-      //detect count prefix in the method name and consider it triggers a reduce
-      if (tree.isCountProjection() == Boolean.TRUE) {
-        return executeReduce(query, designDoc, viewName);
+      if (result.isReduce) {
+        return executeReduce(result.builtQuery, designDoc, viewName);
       } else {
         //otherwise just execute the query
-        return execute(query);
+        return execute(result.builtQuery);
       }
     } catch (PropertyReferenceException e) {
       /*

src/main/java/org/springframework/data/couchbase/repository/query/ViewQueryCreator.java

@@ -30,6 +30,7 @@ import com.couchbase.client.java.document.json.JsonObject;
 import com.couchbase.client.java.view.ViewQuery;
 
 import org.springframework.data.couchbase.core.convert.CouchbaseConverter;
+import org.springframework.data.couchbase.core.view.View;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.repository.query.ParameterAccessor;
 import org.springframework.data.repository.query.parser.AbstractQueryCreator;
@@ -58,18 +59,21 @@ import org.springframework.data.repository.query.parser.PartTree;
  * </ul>
  * </p>
  * Additionally, {@link PartTree#isLimiting()} will use {@link ViewQuery#limit(int) limit}
- * and {@link PartTree#isCountProjection()} will trigger a {@link ViewQuery#reduce() reduce}.
+ * and either {@link View#reduce()} or {@link PartTree#isCountProjection()} will trigger a {@link ViewQuery#reduce() reduce}.
  */
-public class ViewQueryCreator extends AbstractQueryCreator<ViewQuery, ViewQuery> {
+public class ViewQueryCreator extends AbstractQueryCreator<ViewQueryCreator.DerivedViewQuery, ViewQuery> {
 
   private ViewQuery query;
+  private final View viewAnnotation;
   private final PartTree tree;
   private final int treeCount;
   private final CouchbaseConverter converter;
 
-  public ViewQueryCreator(PartTree tree, ParameterAccessor parameters, ViewQuery query, CouchbaseConverter converter) {
+  public ViewQueryCreator(PartTree tree, ParameterAccessor parameters, View viewAnnotation,
+                          ViewQuery query, CouchbaseConverter converter) {
     super(tree, parameters);
     this.query = query;
+    this.viewAnnotation = viewAnnotation;
     this.tree = tree;
     this.converter = converter;
 
@@ -268,7 +272,7 @@ public class ViewQueryCreator extends AbstractQueryCreator<ViewQuery, ViewQuery>
   }
 
   @Override
-  protected ViewQuery complete(ViewQuery criteria, Sort sort) {
+  protected DerivedViewQuery complete(ViewQuery criteria, Sort sort) {
     boolean descending = false;
 
     if (sort != null) {
@@ -290,8 +294,27 @@ public class ViewQueryCreator extends AbstractQueryCreator<ViewQuery, ViewQuery>
       query.limit(tree.getMaxResults());
     }
 
-    query.reduce(tree.isCountProjection() == Boolean.TRUE);
+    boolean isCount = tree.isCountProjection() == Boolean.TRUE;
+    boolean isExplicitReduce = viewAnnotation != null && viewAnnotation.reduce();
+    if (isCount || isExplicitReduce) {
+      query.reduce();
+    }
 
-    return query;
+    return new DerivedViewQuery(query, tree.isLimiting(), isCount || isExplicitReduce);
+  }
+
+  /**
+   * Wrapper class allowing to see downstream if the built query was built with options like reduce and limit.
+   */
+  protected static class DerivedViewQuery {
+    public final ViewQuery builtQuery;
+    public final boolean isLimited;
+    public final boolean isReduce;
+
+    public DerivedViewQuery(ViewQuery builtQuery, boolean isLimited, boolean isReduce) {
+      this.builtQuery = builtQuery;
+      this.isLimited = isLimited;
+      this.isReduce = isReduce;
+    }
   }
 }