[Kde-pim] Review Request 111885: Avoid starting a database transaction in CollectionSync when no updates are needed

[Alessandro Pignotti]

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This is an automatically generated e-mail. To reply, visit:
http://git.reviewboard.kde.org/r/111885/
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(Updated Aug. 5, 2013, 1:14 p.m.)


Review request for Akonadi.


Changes
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Please ignore previous revision


Description
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Rationale: Unconditionally starting a transaction on every collection
sync has an high overhead on disk activity since transaction bookkeping
on the database requires writing to disk. Most often collection sync are
unnecessary since collection are rarely modified, so we end up causing a
write to disk on an operation which would be read-only.

The proposed solution is two run the collection sync in 2 phases:

1) Without starting a transaction, the currently known local collections
are loaded and are compared against the received remote ones. If no
difference is found update is stopped right away

2) If there are differences a transaction is started, local collections
are loaded again to guarantee consistency and the update is applied
inside the transaction


This addresses bug 322083.
    http://bugs.kde.org/show_bug.cgi?id=322083


Diffs (updated)
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  akonadi/collectionsync.cpp 0b85c2be168511486b484c7fcf8de3d157e876d4 
  akonadi/collectionsync_p.h 2ea53c5e0f2d2ce8e1a684b8f685ab6683cd1493 

Diff: http://git.reviewboard.kde.org/r/111885/diff/


Testing
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Code builds and collection fetching seems to be working correctly


Thanks,

Alessandro Pignotti

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