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Implement Message.freeze(), thaw(), and remove_all_tags()

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This commit is contained in:
Sebastian Spaeth 2010-03-18 09:34:10 +01:00
parent 144953116e
commit 4ed01d055a
1 changed files with 118 additions and 8 deletions
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126
cnotmuch/database.py
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@ -143,8 +143,8 @@ class Database(object):
def needs_upgrade(self):
"""Does this database need to be upgraded before writing to it?
If this function returns TRUE then no functions that modify the
database (:meth:`Database.add_message`, :meth:`Database.add_tag`,
If this function returns True then no functions that modify the
database (:meth:`add_message`, :meth:`add_tag`,
:meth:`Directory.set_mtime`, etc.) will work unless :meth:`upgrade`
is called successfully first.
@ -721,15 +721,12 @@ class Message(object):
STATUS.NULL_POINTER
The 'tag' argument is NULL
STATUS.TAG_TOO_LONG
The length of 'tag' is too long
(exceeds Message.NOTMUCH_TAG_MAX)
STATUS.READ_ONLY_DATABASE
Database was opened in read-only mode so message cannot be
modified.
STATUS.NOT_INITIALIZED
The message has not been initialized.
"""
@ -758,15 +755,14 @@ class Message(object):
STATUS.NULL_POINTER
The 'tag' argument is NULL
NOTMUCH_STATUS_TAG_TOO_LONG
STATUS.TAG_TOO_LONG
The length of 'tag' is too long
(exceeds NOTMUCH_TAG_MAX)
NOTMUCH_STATUS_READ_ONLY_DATABASE
STATUS.READ_ONLY_DATABASE
Database was opened in read-only mode so message cannot
be modified.
STATUS.NOT_INITIALIZED
The message has not been initialized.
"""
if self._msg is None:
raise NotmuchError(STATUS.NOT_INITIALIZED)
@ -779,6 +775,120 @@ class Message(object):
raise NotmuchError(status)
def remove_all_tags(self):
"""Removes all tags from the given message.
See :meth:`freeze` for an example showing how to safely
replace tag values.
:returns: STATUS.SUCCESS if the tags were successfully removed.
Raises an exception otherwise.
:exception: :exc:`NotmuchError`. They have the following meaning:
STATUS.READ_ONLY_DATABASE
Database was opened in read-only mode so message cannot
be modified.
STATUS.NOT_INITIALIZED
The message has not been initialized.
"""
if self._msg is None:
raise NotmuchError(STATUS.NOT_INITIALIZED)
status = nmlib.notmuch_message_remove_all_tags(self._msg)
if STATUS.SUCCESS == status:
# return on success
return status
raise NotmuchError(status)
def freeze(self):
"""Freezes the current state of 'message' within the database
This means that changes to the message state, (via :meth:`add_tag`,
:meth:`remove_tag`, and :meth:`remove_all_tags`), will not be
committed to the database until the message is :meth:`thaw`ed.
Multiple calls to freeze/thaw are valid and these calls will
"stack". That is there must be as many calls to thaw as to freeze
before a message is actually thawed.
The ability to do freeze/thaw allows for safe transactions to
change tag values. For example, explicitly setting a message to
have a given set of tags might look like this::
msg.freeze()
msg.remove_all_tags()
for tag in new_tags:
msg.add_tag(tag)
msg.thaw()
With freeze/thaw used like this, the message in the database is
guaranteed to have either the full set of original tag values, or
the full set of new tag values, but nothing in between.
Imagine the example above without freeze/thaw and the operation
somehow getting interrupted. This could result in the message being
left with no tags if the interruption happened after
:meth:`remove_all_tags` but before :meth:`add_tag`.
:returns: STATUS.SUCCESS if the message was successfully frozen.
Raises an exception otherwise.
:exception: :exc:`NotmuchError`. They have the following meaning:
STATUS.READ_ONLY_DATABASE
Database was opened in read-only mode so message cannot
be modified.
STATUS.NOT_INITIALIZED
The message has not been initialized.
"""
if self._msg is None:
raise NotmuchError(STATUS.NOT_INITIALIZED)
status = nmlib.notmuch_message_freeze(self._msg)
if STATUS.SUCCESS == status:
# return on success
return status
raise NotmuchError(status)
def thaw(self):
"""Thaws the current 'message'
Thaw the current 'message', synchronizing any changes that may have
occurred while 'message' was frozen into the notmuch database.
See :meth:`freeze` for an example of how to use this
function to safely provide tag changes.
Multiple calls to freeze/thaw are valid and these calls with
"stack". That is there must be as many calls to thaw as to freeze
before a message is actually thawed.
:returns: STATUS.SUCCESS if the message was successfully frozen.
Raises an exception otherwise.
:exception: :exc:`NotmuchError`. They have the following meaning:
STATUS.UNBALANCED_FREEZE_THAW
An attempt was made to thaw an unfrozen message.
That is, there have been an unbalanced number of calls
to :meth:`freeze` and :meth:`thaw`.
STATUS.NOT_INITIALIZED
The message has not been initialized.
"""
if self._msg is None:
raise NotmuchError(STATUS.NOT_INITIALIZED)
status = nmlib.notmuch_message_thaw(self._msg)
if STATUS.SUCCESS == status:
# return on success
return status
raise NotmuchError(status)
def __str__(self):
"""A message() is represented by a 1-line summary"""
msg = {}