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Date: Sun, 26 Jun 2011 21:27:33 +0100
From: Patrick Totzke <patricktotzke@googlemail.com>
To: notmuch@notmuchmail.org
Subject: xapian exceptions not caught in python bindings?
Message-ID: <20110626202733.GA26837@brick>
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Hi all!
It's me again, with some strange python behaviour :/

When I iterate over threads or messages only partially,
then make changes to the index and continue the iteration,
then I don't necessarily get NotmuchError's but the underlying
libnotmuch seems to call terminate. I get the following two lines on
stderr:
  terminate called after throwing an instance of 'Xapian::DatabaseModifiedE=
rror'
  Aborted
then python aborts without an exception.
This happens on current master with current python bindings. To reproduce
use this to iterate over messages:

------------------%<-------------------
#it_read.py
=66rom notmuch import Query,Database
msgs =3D Database().create_query('*').search_messages()

i=3D0
for m in msgs:
    i=3Di+1
    if i%50=3D=3D0:
        raw_input()
    readit =3D str(m)
------------------>%-------------------

start it, then use this to change the index:

------------------%<-------------------
#it_write.py=20
=66rom notmuch import Query,Database
db =3D Database(mode =3D Database.MODE.READ_WRITE)
msgs =3D Query(db,'*').search_messages()

i=3D0
for m in msgs:
    i=3Di+1
    if i%20=3D=3D0:
        m.add_tag('REMOVEME')
------------------>%-------------------

you have to alternate a bit between hitting enter in the
read code and rerunning the write code.
Read will fail at some point.

The strange thing is that its not consistent:
I stumbled upon this while reading a list of threads from notmuch.threads on
demand. If reading from the iterator catches a NotmuchError, i create a new=
 one
and update my list threads read so far. This does work, but: on every
NotmuchError, I get this on stderr:
 A Xapian exception occurred performing query: The revision being read has =
been discarded - you should call Xapian::Database::reopen() and retry the o=
peration
 Query string was: thread:0000000000001876

After a couple of resets this does not happen again but the next time i read
=66rom an outdated index, the whole UI terminates with the "Aborted" message
stated above.

To sum up, I think there are two bad things happening here:
1) should libnotmuch really print to stderr?
2) the python bindings are either not relaying all exceptions or libnotmuch=
 is not relaying=20
all xapian exceptions in order for the bindings to intercept them

cheers,
/p

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