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Make database connection thread-safe #6030

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Merged
JorisGoosen merged 2 commits into from
Sep 25, 2025
Merged

Make database connection thread-safe #6030

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aba719f
Make database connection thread-safe
boutinb Sep 24, 2025
d7161dd
dont return sqlite3*
JorisGoosen Sep 25, 2025
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11 changes: 7 additions & 4 deletions CommonData/databaseinterface.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2054,7 +2054,10 @@ sqlite3 * DatabaseInterface::_db()
if(_dbCreated && _dbCreator == id)
return _dbCreated;

return load();
if(!_dbs.count(id))
load();

return _dbs.at(id);
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@boutinb boutinb Sep 25, 2025 •
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@RensDofferhoff and me thought also reading in a map is not really thread-safe: a map has no mutex, so if a thread add an element to the map at the same moment that count or at is called, it cannot guarantee the right value.
But as for the moment only one extra thread (the _loaderThread from MainWindow) is used, the map will have in fact only 1 value (the other connection is set in _dbCreated. So that's ok for now...

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@JorisGoosen JorisGoosen Sep 25, 2025

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Which is why I put mutexes in the load and creation function...

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@JorisGoosen JorisGoosen Sep 25, 2025

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And there are waaaaay more threads being used so im not sure why you think there is only one?

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@JorisGoosen JorisGoosen Sep 25, 2025

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class InitColumnTask : public QRunnable look for that

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@RensDofferhoff RensDofferhoff Sep 25, 2025

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It doesn't matter you only guard against concurrent writes into the map with that mutex.
Reads can happen during load and creation.
count() and at() of std::map are not safe when the map is not const.

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@boutinb boutinb Sep 25, 2025

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But then reading in the map should also be enclosed by the mutex.

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@JorisGoosen JorisGoosen Sep 25, 2025

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So we still have that potential problem then you mean?

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@RensDofferhoff RensDofferhoff Sep 25, 2025

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But then reading in the map should also be enclosed by the mutex.

Yes.

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@JorisGoosen JorisGoosen Sep 25, 2025

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well Ill add it to the PR im opening in a few minutes then!

}

void DatabaseInterface::create()
Expand Down Expand Up @@ -2133,7 +2136,7 @@ void DatabaseInterface::preloadInterfaceForThread()
_db();
}

sqlite3* DatabaseInterface::load()
void DatabaseInterface::load()
{
JASPTIMER_SCOPE(DatabaseInterface::load);
assert(!_dbCreated || std::this_thread::get_id() != _dbCreator);
Expand All @@ -2143,7 +2146,7 @@ sqlite3* DatabaseInterface::load()
{
sqlite3* connection = _dbs.at(std::this_thread::get_id());
_loadMutex.unlock();
return connection;
return;
}

if(!std::filesystem::exists(dbFile()))
Expand Down Expand Up @@ -2196,7 +2199,7 @@ sqlite3* DatabaseInterface::load()
}
}

return db;
return;
}

void DatabaseInterface::close()
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4 changes: 1 addition & 3 deletions CommonData/databaseinterface.h
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Expand Up @@ -197,9 +197,7 @@ class DatabaseInterface
void _runStatementsRepeatedly( const std::string & statements, std::function<bool( std::function<void(sqlite3_stmt *stmt)> ** bindParameters, size_t row)> bindParameterFactory, std::function<void(size_t row, size_t repetition, sqlite3_stmt *stmt)> * processRow = nullptr, bool ignoreFails = false);

void create(); ///< Creates a new sqlite database in sessiondir and loads it
sqlite3* load(); ///< Loads a sqlite database from sessiondir (after loading a jaspfile)


void load(); ///< Loads a sqlite database from sessiondir (after loading a jaspfile)

std::map<std::thread::id, sqlite3*> _dbs;
std::thread::id _dbCreator;
Expand Down
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