#2147 Fix for ADD: multiple to many outer joins cause wrong count in distinct count…

Copy of Rolands fix in FOCONIS branch. This also brings over some of the extra tests found there.

Note that the SQL is slightly different from the FOCONIS branch in that there is additional foreign key columns included in the sub-query select clause.

ebean-core/src/main/java/io/ebeaninternal/server/query/CQueryBuilder.java

@@ -571,8 +571,8 @@ class CQueryBuilder {
     private final CQueryPredicates predicates;
     private final SqlTree select;
     private final boolean updateStatement;
-
     private final boolean distinct;
+    private final boolean countSingleAttribute;
     private final String dbOrderBy;
     private boolean useSqlLimiter;
     private boolean hasWhere;
@@ -590,6 +590,7 @@ class CQueryBuilder {
       this.updateStatement = updateStatement;
       this.distinct = query.isDistinct() || select.isSqlDistinct();
       this.dbOrderBy = predicates.getDbOrderBy();
+      this.countSingleAttribute = query.isCountDistinct() && query.isSingleAttribute();
     }
 
     private void appendSelect() {
@@ -601,8 +602,13 @@ class CQueryBuilder {
         if (!useSqlLimiter) {
           appendSelectDistinct();
         }
-        if (query.isCountDistinct() && query.isSingleAttribute()) {
-          sb.append("r1.attribute_, count(*) from (select ").append(select.getSelectSql()).append(" as attribute_");
+        if (countSingleAttribute) {
+          sb.append("r1.attribute_, count(*) from (select ");
+          if (distinct) {
+            sb.append("distinct t0.");
+            sb.append(request.getBeanDescriptor().getIdProperty().getDbColumn()).append(", ");
+          }
+          sb.append(select.getSelectSql()).append(" as attribute_");
         } else {
           sb.append(select.getSelectSql());
         }
@@ -621,7 +627,7 @@ class CQueryBuilder {
 
     private void appendSelectDistinct() {
       sb.append("select ");
-      if (distinct) {
+      if (distinct && !countSingleAttribute) {
         if (request.isInlineCountDistinct()) {
           sb.append("count(");
         }
@@ -730,7 +736,7 @@ class CQueryBuilder {
         sb.append(" order by ").append(dbOrderBy);
       }
 
-      if (query.isCountDistinct() && query.isSingleAttribute()) {
+      if (countSingleAttribute) {
         sb.append(") r1 group by r1.attribute_");
         sb.append(toSql(query.getCountDistinctOrder()));
       }