fix(core): fix join with group by

core/src/main/java/cn/edu/tsinghua/iginx/sql/statement/frompart/SubQueryFromPart.java

@@ -71,6 +71,10 @@ public boolean hasAlias() {
 
   @Override
   public boolean hasSinglePrefix() {
+    if (!subQuery.isSimpleQuery()) {
+      return false;
+    }
+
     if (hasAlias()) {
       return true;
     }

core/src/main/java/cn/edu/tsinghua/iginx/sql/statement/select/BinarySelectStatement.java

@@ -96,4 +96,9 @@ public void initFreeVariables() {
   public List<Pair<String, String>> getSubQueryAliasList(String alias) {
     return leftQuery.getSubQueryAliasList(alias);
   }
+
+  @Override
+  public boolean isSimpleQuery() {
+    return leftQuery.isSimpleQuery() && rightQuery.isSimpleQuery();
+  }
 }

core/src/main/java/cn/edu/tsinghua/iginx/sql/statement/select/SelectStatement.java

@@ -138,6 +138,8 @@ public void addFreeVariable(String freeVariable) {
 
   public abstract List<Pair<String, String>> getSubQueryAliasList(String alias);
 
+  public abstract boolean isSimpleQuery();
+
   public enum SelectStatementType {
     UNARY,
     BINARY

core/src/main/java/cn/edu/tsinghua/iginx/sql/statement/select/UnarySelectStatement.java

@@ -451,6 +451,11 @@ public void setSlideDistance(long slideDistance) {
     this.groupByClause.setSlideDistance(slideDistance);
   }
 
+  @Override
+  public boolean isSimpleQuery() {
+    return groupByClause.getQueryType() == QueryType.SimpleQuery;
+  }
+
   public QueryType getQueryType() {
     return groupByClause.getQueryType();
   }

test/src/test/java/cn/edu/tsinghua/iginx/integration/func/sql/SQLSessionIT.java

@@ -2721,6 +2721,21 @@ public void testJoinWithGroupBy() {
             + "+-----+----+\n"
             + "Total line number = 1\n";
     executor.executeAndCompare(query, expected);
+
+    query =
+        "select test1.d, sum(avg_a) from test1 join (select d, avg(a) as avg_a from test2 group by d) on test1.d = test2.d group by test1.d;";
+    expected =
+        "ResultSets:\n"
+            + "+-------+----------+\n"
+            + "|test1.d|sum(avg_a)|\n"
+            + "+-------+----------+\n"
+            + "|   val5|       2.0|\n"
+            + "|   val3|       2.0|\n"
+            + "|   val2|       4.0|\n"
+            + "|   val1|       4.0|\n"
+            + "+-------+----------+\n"
+            + "Total line number = 4\n";
+    executor.executeAndCompare(query, expected);
   }
 
   @Test