|Summary:||akonadictl; sqlite: Error moving orphan items to collection 242 : Expression tree is too large (maximum depth 1000)|
|Product:||[Frameworks and Libraries] Akonadi||Reporter:||Erik Quaeghebeur <bugs.kde.org>|
|Component:||general||Assignee:||kdepim bugs <kdepim-bugs>|
|Latest Commit:||Version Fixed In:|
Description Erik Quaeghebeur 2022-03-17 12:54:57 UTC
SUMMARY I use akonadi with the sqlite backend. Running akonadictl results in an error that seems to result from akonadi giving sqlite a query that is too long: --- $ akonadictl fsck […] Checking collection tree consistency... Looking for items not belonging to a valid collection... Found 110689 orphan items. Error moving orphan items to collection 242 : Expression tree is too large (maximum depth 1000) Kon statement niet uitvoeren […] --- ("Kon statement niet uitvoeren" means "Could not execute statement") STEPS TO REPRODUCE 1. run akonadictl fsck again OBSERVED RESULT Error moving orphan items to collection 242 : Expression tree is too large (maximum depth 1000) Kon statement niet uitvoeren EXPECTED RESULT orphans are cleaned up SOFTWARE/OS VERSIONS KDE Plasma Version: 5.23.5 KDE Frameworks Version: 5.90.0 Qt Version: 5.15.2 (with https://community.kde.org/Qt5PatchCollection) ADDITIONAL INFORMATION I think this is sqlite-specific, given some search results on the web
Comment 1 Erik Quaeghebeur 2022-03-20 12:37:32 UTC
I have investigated a bit further. Using a GUI for sqlite (sqlitebrowser), I familiarized myself a bit with the database and then looked into what was going on here: --- select distinct "collectionId" as "id" from "PimItemTable" except select distinct "id" from "CollectionTable" order by "id"; --- This returned 52 collections that where referenced by items, but apparently do not exist anymore. --- select "id" as "itemId", "collectionId" from "PimItemTable" where "collectionId" not in (select distinct "id" from "CollectionTable") order by "collectionId"; --- This returned 110689 items, the same as reported by akonadictl, so indeed these were the orphans mentioned. --- delete from "PimItemTable" where "collectionId" not in (select distinct "id" from "CollectionTable"); --- To fix the issue, I just removed them rather than creating a lost+found(?) collection (with id 242?) and updating the collectionId of the items to 242. After vacuuming (‘compress database’ under ‘Extra’ menu in sqlitebrowser), my database shrunk to less than half the size it had before (600+ to ~250 MB). So what seems to go wrong is that in the code *the list of orphans* resulting from a first query is used to build a second query to change their collectionId. Because this list is absurdly long, sqlite bails out. A possible fix would be to first find out if there are orphan collections (my first query listed) and if so, create as needed the lost+found collection and update the corresponding items in the way done by my last query above. Next, I dived into the code. I think the function in question can be found at https://invent.kde.org/pim/akonadi/-/blob/master/src/server/storagejanitor.cpp#L277. There, one can indeed see that a list of orphans is created on the C++ side (in the variable imapIds) and subsequently used to create the query to clean up the orphans. While the Qt functions for creating queries are mostly gibberish to me, what I can deduce, is that this is done in a roundabout, inefficient way, as compared to what my queries above do. Is there a reason for this? Finally, a point that must be addressed is why such orphans can even exist, as in the database schema for the creation of PimItemTable, I see: … collectionId BIGINT … CONSTRAINT PimItemTablecollectionId_Collectionid_fk FOREIGN KEY (collectionId) REFERENCES CollectionTable(id) ON UPDATE CASCADE ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED … which should in principle cascade the deletion of the collection to the deletion of items within that collection. I do not know what could have gone wrong, but it is worrying. N.B.: The above column definition+constraint can more compactly be done as collectionId BIGINT REFERENCES CollectionTable(id) ON UPDATE CASCADE ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED using the concept of column constraint: https://www.sqlite.org/syntax/column-constraint.html.