MDEV-4326 fix.

Removed "optimization" which caused preoblems on second execution of PS with string parameter in LIMIT clause.

Fixed test_bug43560 to be able to skipp it if connection is UNIX socket.

sql/sql_prepare.cc

@@ -787,7 +787,7 @@ static bool insert_params_with_log(Prepared_statement *stmt, uchar *null_array,
         if (param->state == Item_param::NO_VALUE)
           DBUG_RETURN(1);
 
-        if (param->limit_clause_param && param->item_type != Item::INT_ITEM)
+        if (param->limit_clause_param)
         {
           param->set_int(param->val_int(), MY_INT64_NUM_DECIMAL_DIGITS);
           param->item_type= Item::INT_ITEM;

tests/mysql_client_test.c

@@ -16750,7 +16750,11 @@ static void test_bug43560(void)
     fprintf(stdout, "Skipping test_bug43560: server not DEBUG version\n");
     DBUG_VOID_RETURN;
   }
-
+  if (opt_unix_socket)
+  {
+    fprintf(stdout, "Skipping test_bug43560: connected via UNIX socket\n");
+    DBUG_VOID_RETURN;
+  }
   /*
     Set up a separate connection for this test to avoid messing up the
     general MYSQL object used in other subtests. Use TCP protocol to avoid
@@ -17541,6 +17545,109 @@ static void test_bug13001491()
   myquery(rc);
 }
 
+static void test_mdev4326()
+{
+  MYSQL_STMT   *stmt;
+  MYSQL_BIND    bind;
+  char query[]= "SELECT * FROM mysql.user LIMIT ?";
+  char str_data[]= "1";
+  unsigned long length= 0;
+  int int_data= 1;
+  int rc, count;
+  my_bool is_null= 0;
+  my_bool error= 0;
+  myheader("test_mdev4326");
+
+  rc= mysql_change_user(mysql, opt_user, opt_password, "mysql");
+  myquery(rc);
+
+  rc= mysql_query(mysql, "SET GLOBAL general_log = 1");
+  myquery(rc);
+
+  stmt= mysql_stmt_init(mysql);
+  check_stmt(stmt);
+
+  /* Numeric parameter test */
+
+  rc= mysql_stmt_prepare(stmt, query, strlen(query));
+  check_execute(stmt, rc);
+  check_stmt(stmt);
+  verify_param_count(stmt, 1);
+
+  memset((char *)&bind, 0, sizeof(bind));
+  bind.buffer_type= MYSQL_TYPE_LONG;
+  bind.buffer= (char *)&int_data;
+  bind.is_null= &is_null;
+  bind.length= &length;
+  bind.error= &error;
+
+  rc= mysql_stmt_bind_param(stmt, &bind);
+  check_execute(stmt, rc);
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  count= 0;
+  while (!(rc= mysql_stmt_fetch(stmt)))
+    count++;
+  DIE_UNLESS(count == 1);
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  count= 0;
+  while (!(rc= mysql_stmt_fetch(stmt)))
+    count++;
+  DIE_UNLESS(count == 1);
+  int_data= 0;
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  count= 0;
+  while (!(rc= mysql_stmt_fetch(stmt)))
+    count++;
+  DIE_UNLESS(count == 0);
+  rc= mysql_stmt_close(stmt);
+  check_execute(stmt, rc);
+
+  /* String parameter test */
+
+  stmt= mysql_stmt_init(mysql);
+  rc= mysql_stmt_prepare(stmt, query, strlen(query));
+  check_execute(stmt, rc);
+  check_stmt(stmt);
+  verify_param_count(stmt, 1);
+
+  memset((char *)&bind, 0, sizeof(bind));
+  bind.buffer_type= MYSQL_TYPE_STRING;
+  bind.buffer= (char *)str_data;
+  length= bind.buffer_length= sizeof(str_data);
+  bind.is_null= &is_null;
+  bind.length= &length;
+  bind.error= &error;
+
+  rc= mysql_stmt_bind_param(stmt, &bind);
+  check_execute(stmt, rc);
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  count= 0;
+  while (!(rc= mysql_stmt_fetch(stmt)))
+    count++;
+  DIE_UNLESS(count == 1);
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  count= 0;
+  while (!(rc= mysql_stmt_fetch(stmt)))
+    count++;
+  DIE_UNLESS(count == 1);
+  str_data[0]= '0';
+  rc= mysql_stmt_execute(stmt);
+  check_execute(stmt, rc);
+  count= 0;
+  while (!(rc= mysql_stmt_fetch(stmt)))
+    count++;
+  DIE_UNLESS(count == 0);
+  rc= mysql_stmt_close(stmt);
+  check_execute(stmt, rc);
+
+  rc= mysql_change_user(mysql, opt_user, opt_password, current_db);
+  myquery(rc);
+}
 
 static struct my_tests_st my_tests[]= {
   { "disable_query_logs", disable_query_logs },
@@ -17790,6 +17897,7 @@ static struct my_tests_st my_tests[]= {
   { "test_bug58036", test_bug58036 },
   { "test_bug56976", test_bug56976 },
   { "test_bug13001491", test_bug13001491 },
+  { "test_mdev4326", test_mdev4326 },
   { 0, 0 }
 };