fix for bug #11904 (select statement, cursor, grouping wrong results)

sql/sql_select.cc

@@ -10256,6 +10256,7 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
 	       bool end_of_records)
 {
   int idx= -1;
+  enum_nested_loop_state ok_code= NESTED_LOOP_OK;
   DBUG_ENTER("end_send_group");
 
   if (!join->first_record || end_of_records ||
@@ -10320,7 +10321,11 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
             There is a server side cursor and all rows
             for this fetch request are sent.
           */
-          DBUG_RETURN(NESTED_LOOP_CURSOR_LIMIT);
+          /*
+            Preventing code duplication. When finished with the group reset
+            the group functions and copy_fields. We fall through. bug #11904
+          */
+          ok_code= NESTED_LOOP_CURSOR_LIMIT;
         }
       }
     }
@@ -10333,12 +10338,16 @@ end_send_group(JOIN *join, JOIN_TAB *join_tab __attribute__((unused)),
     }
     if (idx < (int) join->send_group_parts)
     {
+      /*
+        This branch is executed also for cursors which have finished their
+        fetch limit - the reason for ok_code.
+      */
       copy_fields(&join->tmp_table_param);
       if (init_sum_functions(join->sum_funcs, join->sum_funcs_end[idx+1]))
 	DBUG_RETURN(NESTED_LOOP_ERROR);
       if (join->procedure)
 	join->procedure->add();
-      DBUG_RETURN(NESTED_LOOP_OK);
+      DBUG_RETURN(ok_code);
     }
   }
   if (update_sum_func(join->sum_funcs))

tests/mysql_client_test.c

@@ -14179,6 +14179,81 @@ static void test_bug11901()
   myquery(rc);
 }
 
+/* Bug#11904: mysql_stmt_attr_set CURSOR_TYPE_READ_ONLY grouping wrong result */
+
+static void test_bug11904()
+{
+  MYSQL_STMT *stmt1;
+  int rc;
+  const char *stmt_text;
+  const ulong type= (ulong)CURSOR_TYPE_READ_ONLY;
+  MYSQL_BIND bind[2];
+  int country_id=0;
+  char row_data[11]= {0};
+
+  myheader("test_bug11904");
+
+  /* create tables */
+  rc= mysql_query(mysql, "DROP TABLE IF EXISTS bug11904b");
+  myquery(rc);
+  rc= mysql_query(mysql, "CREATE TABLE bug11904b (id int, name char(10), primary key(id, name))");
+  myquery(rc);
+
+  rc= mysql_query(mysql, "INSERT INTO bug11904b VALUES (1, 'sofia'), (1,'plovdiv'),"
+                          " (1,'varna'), (2,'LA'), (2,'new york'), (3,'heidelberg'),"
+                          " (3,'berlin'), (3, 'frankfurt')");
+
+  myquery(rc);
+  mysql_commit(mysql);
+  /* create statement */
+  stmt1= mysql_stmt_init(mysql);
+  mysql_stmt_attr_set(stmt1, STMT_ATTR_CURSOR_TYPE, (const void*) &type);
+
+  stmt_text= "SELECT id, MIN(name) FROM bug11904b GROUP BY id";
+
+  rc= mysql_stmt_prepare(stmt1, stmt_text, strlen(stmt_text));
+  check_execute(stmt1, rc);
+
+  memset(bind, 0, sizeof(bind));
+  bind[0].buffer_type= MYSQL_TYPE_LONG;
+  bind[0].buffer=& country_id;
+  bind[0].buffer_length= 0;
+  bind[0].length= 0;
+
+  bind[1].buffer_type= MYSQL_TYPE_STRING;
+  bind[1].buffer=& row_data;
+  bind[1].buffer_length= sizeof(row_data) - 1;
+  bind[1].length= 0;
+
+  rc= mysql_stmt_bind_result(stmt1, bind);
+  check_execute(stmt1, rc);
+
+  rc= mysql_stmt_execute(stmt1);
+  check_execute(stmt1, rc);
+
+  rc= mysql_stmt_fetch(stmt1);
+  check_execute(stmt1, rc);
+  DIE_UNLESS(country_id == 1);
+  DIE_UNLESS(memcmp(row_data, "plovdiv", 7) == 0);
+
+  rc= mysql_stmt_fetch(stmt1);
+  check_execute(stmt1, rc);
+  DIE_UNLESS(country_id == 2);
+  DIE_UNLESS(memcmp(row_data, "LA", 2) == 0);
+
+  rc= mysql_stmt_fetch(stmt1);
+  check_execute(stmt1, rc);
+  DIE_UNLESS(country_id == 3);
+  DIE_UNLESS(memcmp(row_data, "berlin", 6) == 0);
+
+  rc= mysql_stmt_close(stmt1);
+  check_execute(stmt1, rc);
+
+  rc= mysql_query(mysql, "drop table bug11904b");
+  myquery(rc);
+}
+
+
 /* Bug#12243: multiple cursors, crash in a fetch after commit. */
 
 static void test_bug12243()
@@ -14487,6 +14562,7 @@ static struct my_tests_st my_tests[]= {
   { "test_bug12001", test_bug12001 },
   { "test_bug11909", test_bug11909 },
   { "test_bug11901", test_bug11901 },
+  { "test_bug11904", test_bug11904 },
   { "test_bug12243", test_bug12243 },
   { 0, 0 }
 };