Generate the GROUP BY clause automatically.

We generate it when it is empty and the SELECT clause includes any aggregate functions.

Author: nakamura-to

doma-core/src/main/java/org/seasar/doma/jdbc/criteria/query/SelectBuilder.java

@@ -1,5 +1,7 @@
 package org.seasar.doma.jdbc.criteria.query;
 
+import static java.util.stream.Collectors.toList;
+
 import java.util.List;
 import java.util.Objects;
 import java.util.function.Function;
@@ -14,6 +16,7 @@
 import org.seasar.doma.jdbc.criteria.context.Join;
 import org.seasar.doma.jdbc.criteria.context.JoinKind;
 import org.seasar.doma.jdbc.criteria.context.SelectContext;
+import org.seasar.doma.jdbc.criteria.declaration.AggregateFunction;
 import org.seasar.doma.jdbc.criteria.def.EntityDef;
 import org.seasar.doma.jdbc.criteria.def.PropertyDef;
 
@@ -128,6 +131,16 @@ private void where() {
   }
 
   private void groupBy() {
+    if (context.groupBy.isEmpty()) {
+      List<PropertyDef<?>> propertyDefs = context.allPropertyDefs();
+      if (propertyDefs.stream().anyMatch(p -> p instanceof AggregateFunction<?>)) {
+        List<PropertyDef<?>> groupKeys =
+            propertyDefs.stream()
+                .filter(p -> !(p instanceof AggregateFunction<?>))
+                .collect(toList());
+        context.groupBy.addAll(groupKeys);
+      }
+    }
     if (!context.groupBy.isEmpty()) {
       buf.appendSql(" group by ");
       for (PropertyDef<?> p : context.groupBy) {

doma-core/src/test/java/org/seasar/doma/jdbc/criteria/NativeSqlSelectTest.java

@@ -709,6 +709,17 @@ void groupBy_empty() {
     assertEquals("select t0_.ID from EMP t0_", sql.getFormattedSql());
   }
 
+  @Test
+  void groupBy_auto_generation() {
+    Emp_ e = new Emp_();
+    Buildable<?> stmt = nativeSql.from(e).select(e.id, e.salary, count(e.name), max(e.id));
+
+    Sql<?> sql = stmt.asSql();
+    assertEquals(
+        "select t0_.ID, t0_.SALARY, count(t0_.NAME), max(t0_.ID) from EMP t0_ group by t0_.ID, t0_.SALARY",
+        sql.getFormattedSql());
+  }
+
   @Test
   void having() {
     Emp_ e = new Emp_();

test-criteria/src/test/java/example/NativeSqlSelectTest.java

@@ -177,6 +177,17 @@ void groupBy() {
     assertEquals(3, list.size());
   }
 
+  @Test
+  void groupBy_auto_generation() {
+    Employee_ e = new Employee_();
+
+    Listable<Tuple2<Integer, Long>> stmt = nativeSql.from(e).select(e.departmentId, count());
+
+    List<Tuple2<Integer, Long>> list = stmt.fetch();
+
+    assertEquals(3, list.size());
+  }
+
   @Test
   void having() {
     Employee_ e = new Employee_();