A fix and a test case for Bug#11909 "mysql_stmt_attr_set

CURSOR_TYPE_READ_ONLY nested queries corrupt result"


sql/sql_prepare.cc:
  If there is a cursor, use its protocol for fetch: 
  Protocol instances have a state and thd->protocol_prep can't
  be used for multiple cursors.
sql/sql_select.cc:
  - init Cursor::protocol
sql/sql_select.h:
  - add Cursor::protocol
tests/mysql_client_test.c:
  A test case for Bug#11909 "mysql_stmt_attr_set CURSOR_TYPE_READ_ONLY
   nested queries corrupt result"

sql/sql_prepare.cc

@@ -88,6 +88,7 @@ class Prepared_statement: public Statement
 {
 public:
   THD *thd;
+  Protocol *protocol;
   Item_param **param_array;
   uint param_count;
   uint last_errno;
@@ -2021,6 +2022,7 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
         DBUG_VOID_RETURN;
       /* If lex->result is set, mysql_execute_command will use it */
       stmt->lex->result= &cursor->result;
+      stmt->protocol= &cursor->protocol;
       thd->lock_id= &cursor->lock_id;
     }
   }
@@ -2055,7 +2057,7 @@ void mysql_stmt_execute(THD *thd, char *packet, uint packet_length)
   }
   mysql_log.write(thd, thd->command, "[%lu] %s", stmt->id, thd->query);
 
-  thd->protocol= &thd->protocol_prep;           // Switch to binary protocol
+  thd->protocol= stmt->protocol;                // Switch to binary protocol
   if (!(specialflag & SPECIAL_NO_PRIOR))
     my_pthread_setprio(pthread_self(),QUERY_PRIOR);
   mysql_execute_command(thd);
@@ -2247,7 +2249,7 @@ void mysql_stmt_fetch(THD *thd, char *packet, uint packet_length)
   if (!(specialflag & SPECIAL_NO_PRIOR))
     my_pthread_setprio(pthread_self(), QUERY_PRIOR);
 
-  thd->protocol= &thd->protocol_prep;           // Switch to binary protocol
+  thd->protocol= stmt->protocol;                // Switch to binary protocol
   cursor->fetch(num_rows);
   thd->protocol= &thd->protocol_simple;         // Use normal protocol
 
@@ -2419,6 +2421,7 @@ Prepared_statement::Prepared_statement(THD *thd_arg)
              thd_arg->variables.query_alloc_block_size,
              thd_arg->variables.query_prealloc_size),
   thd(thd_arg),
+  protocol(&thd_arg->protocol_prep),
   param_array(0),
   param_count(0),
   last_errno(0)

sql/sql_select.cc

@@ -1715,6 +1715,7 @@ JOIN::destroy()
 Cursor::Cursor(THD *thd)
   :Query_arena(&main_mem_root, INITIALIZED),
    join(0), unit(0),
+   protocol(thd),
    close_at_commit(FALSE)
 {
   /* We will overwrite it at open anyway. */

sql/sql_select.h

@@ -396,6 +396,7 @@ class Cursor: public Sql_alloc, public Query_arena
   };
   Engine_info ht_info[MAX_HA];
 public:
+  Protocol_prep protocol;
   Item_change_list change_list;
   select_send result;
   THR_LOCK_OWNER lock_id;

tests/mysql_client_test.c

@@ -13932,6 +13932,125 @@ static void test_bug12001()
   DIE_UNLESS(res==1);
 }
 
+
+/* Bug#11909: wrong metadata if fetching from two cursors */
+
+static void test_bug11909()
+{
+  MYSQL_STMT *stmt1, *stmt2;
+  MYSQL_BIND bind[7];
+  int rc;
+  char firstname[20], midinit[20], lastname[20], workdept[20];
+  ulong firstname_len, midinit_len, lastname_len, workdept_len;
+  uint32 empno;
+  double salary;
+  float bonus;
+  const char *stmt_text;
+
+  myheader("test_bug11909");
+
+  stmt_text= "drop table if exists t1";
+  rc= mysql_real_query(mysql, stmt_text, strlen(stmt_text));
+  myquery(rc);
+
+  stmt_text= "create table t1 ("
+    "  empno int(11) not null, firstname varchar(20) not null,"
+    "  midinit varchar(20) not null, lastname varchar(20) not null,"
+    "  workdept varchar(6) not null, salary double not null,"
+    "  bonus float not null, primary key (empno)"
+    ") default charset=latin1 collate=latin1_bin";
+  rc= mysql_real_query(mysql, stmt_text, strlen(stmt_text));
+  myquery(rc);
+
+  stmt_text= "insert into t1 values "
+    "(10, 'CHRISTINE', 'I', 'HAAS',     'A00', 52750, 1000), "
+    "(20, 'MICHAEL',   'L', 'THOMPSON', 'B01', 41250, 800),"
+    "(30, 'SALLY',     'A', 'KWAN',     'C01', 38250, 800),"
+    "(50, 'JOHN',      'B', 'GEYER',    'E01', 40175, 800), "
+    "(60, 'IRVING',    'F', 'STERN',    'D11', 32250, 500)";
+  rc= mysql_real_query(mysql, stmt_text, strlen(stmt_text));
+  myquery(rc);
+
+  /* ****** Begin of trace ****** */
+
+  stmt1= open_cursor("SELECT empno, firstname, midinit, lastname,"
+                     "workdept, salary, bonus FROM t1");
+
+  bzero(bind, sizeof(bind));
+  bind[0].buffer_type= MYSQL_TYPE_LONG;
+  bind[0].buffer= (void*) &empno;
+
+  bind[1].buffer_type= MYSQL_TYPE_VAR_STRING;
+  bind[1].buffer= (void*) firstname;
+  bind[1].buffer_length= sizeof(firstname);
+  bind[1].length= &firstname_len;
+
+  bind[2].buffer_type= MYSQL_TYPE_VAR_STRING;
+  bind[2].buffer= (void*) midinit;
+  bind[2].buffer_length= sizeof(midinit);
+  bind[2].length= &midinit_len;
+
+  bind[3].buffer_type= MYSQL_TYPE_VAR_STRING;
+  bind[3].buffer= (void*) lastname;
+  bind[3].buffer_length= sizeof(lastname);
+  bind[3].length= &lastname_len;
+
+  bind[4].buffer_type= MYSQL_TYPE_VAR_STRING;
+  bind[4].buffer= (void*) workdept;
+  bind[4].buffer_length= sizeof(workdept);
+  bind[4].length= &workdept_len;
+
+  bind[5].buffer_type= MYSQL_TYPE_DOUBLE;
+  bind[5].buffer= (void*) &salary;
+
+  bind[6].buffer_type= MYSQL_TYPE_FLOAT;
+  bind[6].buffer= (void*) &bonus;
+  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);
+  DIE_UNLESS(rc == 0);
+  DIE_UNLESS(empno == 10);
+  DIE_UNLESS(strcmp(firstname, "CHRISTINE") == 0);
+  DIE_UNLESS(strcmp(midinit, "I") == 0);
+  DIE_UNLESS(strcmp(lastname, "HAAS") == 0);
+  DIE_UNLESS(strcmp(workdept, "A00") == 0);
+  DIE_UNLESS(salary == (double) 52750.0);
+  DIE_UNLESS(bonus == (float) 1000.0);
+
+  stmt2= open_cursor("SELECT empno, firstname FROM t1");
+  rc= mysql_stmt_bind_result(stmt2, bind);
+  check_execute(stmt2, rc);
+
+  rc= mysql_stmt_execute(stmt2);
+  check_execute(stmt2, rc);
+
+  rc= mysql_stmt_fetch(stmt2);
+  DIE_UNLESS(rc == 0);
+
+  DIE_UNLESS(empno == 10);
+  DIE_UNLESS(strcmp(firstname, "CHRISTINE") == 0);
+
+  rc= mysql_stmt_reset(stmt2);
+  check_execute(stmt2, rc);
+
+  /* ERROR: next statement should return 0 */
+
+  rc= mysql_stmt_fetch(stmt1);
+  DIE_UNLESS(rc == 0);
+
+  mysql_stmt_close(stmt1);
+  mysql_stmt_close(stmt2);
+  rc= mysql_rollback(mysql);
+  myquery(rc);
+
+  rc= mysql_query(mysql, "drop table t1");
+  myquery(rc);
+}
+
 /*
   Read and parse arguments and MySQL options from my.cnf
 */
@@ -14178,6 +14297,7 @@ static struct my_tests_st my_tests[]= {
   { "test_bug11037", test_bug11037 },
   { "test_bug10760", test_bug10760 },
   { "test_bug12001", test_bug12001 },
+  { "test_bug11909", test_bug11909 },
   { 0, 0 }
 };