Converting offline twice within the same instance causing unusable offline state

[qgib]

Author Name: Drew Nix (Drew Nix)
Original Redmine Issue: 10537
Affected QGIS version: master
Redmine category:c++_plugins/offline_editing
Assignee: Alessandro Pasotti

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Problem Description:
Converting offline twice within the same running project instance causes unusable offline state.

Problem Result:
After which the "Convert to Offline Project" is grayed out. The project will no longer synchronize and the project is stuck in an Offline State.

If the project is saved, upon opening the same scenario applies.

The only fix to this is to open the project file in a text editor and delete the offline information and save the file. This is impossible for most of our users.

Steps to reproduce:
Open Qgis
Add PostGIS vector layer
Database > Offline Editing > Convert to Offline Project
Offline data: C:/OSGEO4W/bin/offline.sqlite
Select PostGIS vector layer
Database > Offline Editing > Syncronize
Database > Offline Editing > Convert to Offline Project
Offline data: C:/OSGEO4W/bin/offline.sqlite (Same dataset)

Errors:
table 'tog_indices' already exists
table 'log_layer_ids' already exists
table 'log_fids' already exists
table 'log_added_attrs' already exists
table 'log_added_features' already exists
table 'log_removed_features' already exists
table 'log_feature_updates' already exists
table 'log_geometry_updates' already exists

table '<PostGIS_LAYER>' already exists

[qgib]

Author Name: Giovanni Manghi (@gioman)

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On Linux I can't confirm the error messages and the offline db in a unusable state, but I can confirm that overwriting an already existing offline db with a new one causes strange things to happen (the most obvious is the loss of features). If each time layer(s) are placed off-line is used a new offline db (no overwriting) then things are ok.

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• operating_system was changed from Windows 7 to
• os_version was changed from 64 bit to

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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• category_id was configured as C++ Plugins

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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• fixed_version_id was changed from Version 2.4 to Future Release - High Priority

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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• category_id was changed from C++ Plugins to C++ plugins/Offline editing

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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• subject was changed from Offline Editing - Converting offline twice within the same instance causing unusable offline state to Converting offline twice within the same instance causing unusable offline state

[qgib]

Author Name: Giovanni Manghi (@gioman)

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found that this is a regression since qgis 2.0.1, where overwriting the already existing offline db worked without issues.

Moreover now on QGIS master on Linux it causes a crash

Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Warning: Object::disconnect: Unexpected null parameter
Fatal: ASSERT failure in QList<T>::at: "index out of range", file /usr/include/qt4/QtCore/qlist.h, line 469
QGIS died on signal -1Could not attach to process.  If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user.  For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.
No thread selected
No stack.
gdb returned 0
Aborted

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• priority_id was changed from High to Severe/Regression
• fixed_version_id was changed from Future Release - High Priority to Version 2.6

[qgib]

Author Name: Jürgen Fischer (@jef-n)

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• fixed_version_id was changed from Version 2.6 to Future Release - High Priority

[qgib]

Author Name: Matthias Kuhn (@m-kuhn)

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• Concerning the crash, which operation have you been performing?

• We could delete the offline db after going online. Or rename it to a backup copy which will eventually be overwritten on the next sync. That way one would always have a backup copy. Although I am not sure if it will be that easy to recover information from it.

• When going offline and the target file already exists, I think a warning should be raised, asking for confirmation if it's ok to overwrite.

• In the future this should possibly be enhanced with a recovery option to synchronized leftover data in not-yet (fully) synchronized offline databases.

Comments?

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• status_id was changed from Open to Feedback

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Matthias Kuhn wrote:

• Concerning the crash, which operation have you been performing?

nothing special, adding/editing one feature.

• We could delete the offline db after going online. Or rename it to a backup copy which will eventually be overwritten on the next sync. That way one would always have a backup copy. Although I am not sure if it will be that easy to recover information from it.

• When going offline and the target file already exists, I think a warning should be raised, asking for confirmation if it's ok to overwrite.

• In the future this should possibly be enhanced with a recovery option to synchronized leftover data in not-yet (fully) synchronized offline databases.

Comments?

it seems to me a good plan :)

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• status_id was changed from Feedback to Open

[qgib]

Author Name: Drew Nix (Drew Nix)

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What about a fail-back as well (to a proper online state) if converting offline fails?

-- happy to see some activity here ;)

[qgib]

Author Name: Alessandro Pasotti (@elpaso)

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• assigned_to_id was configured as Alessandro Pasotti

[qgib]

Author Name: Anónimo (Anónimo)

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Fixed in changeset "f045492ed54a528263444824e7bbf3317d6d80e2".

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• status_id was changed from Open to Closed