DatabaseModifiedError, how to handle it correctly when searching?

[Yuan Fu]

> On Aug 30, 2021, at 6:36 PM, Yuan Fu <casouri at gmail.com> wrote:
> 
> 
> 
>> On Aug 30, 2021, at 2:48 AM, Eric Wong <e at 80x24.org> wrote:
>> 
>> Yuan Fu <casouri at gmail.com> wrote:
>>> The starter guide [1] mentioned that searching could result in DatabaseModifiedError, and I need to reopen the database should it happen. However, I couldn’t figure out which functions throw that error, I looked at Enquire.get_mset(), etc, and none of them says they throw this error. How should I correctly handle this?
>>> 
>>> [1] https://getting-started-with-xapian.readthedocs.io/en/latest/practical_example/searching/database_modified.html
>> 
>> I think pretty much all Xapian functions which read the database
>> can throw DatabaseModifiedError.  I've been wrapping all
>> accesses with `eval {}' (Perl's standard exception trapping
>> mechanism).
> 
> Ah, I see, so for C++ it would look something like this, I assume?
> 
>      for (int i = 0; i < 2; i++)
>        {
>          try
>            {
>              database.replace_document (termID, new_doc);
>              break;
>            }
>          catch (Xapian::DatabaseModifiedError &e)
>            {
>              database.reopen();
>            }
>        }

Oops, it should have been

  int try_count = 0;
  while (true)
    {
      try
        {
          (do stuff)
          break;
        }
      catch (Xapian::DatabaseModifiedError &e)
        {
          if (try_count > 0) throw e;
          database.reopen();
          try_count++;
        }
    }

Sorry for the noise :-(

Yuan