[odb-users] strange lazy section

[Патрушев Данил Андреевич]

Hi, we are observing strange behavior of lazy loaded sections. The content of a lazy loaded QByteArray, in case its length exceeds 256 bytes, seems to be corrupted. With eager loading enabled, the section is loaded as expected.

Code:


#pragma db object

struct DbObject

{

#pragma db id auto

    quint64 id;

#pragma db load(lazy)

    odb::section extras_;

#pragma db section(extras_)

    QByteArray content;

};



void persist(DbObject& obj1, DbObject& obj2)

{

    odb::pgsql::database connection(//database connection details);

    odb::transaction tran(connection.begin());

    connection.persist(obj1);

    connection.persist(obj2);

    tran.commit();


}


void read()

{

    odb::pgsql::database connection(//database connection details);

    odb::transaction tran(connection.begin());

    odb::result<DbObject> result(connection.query<DbObject>());

    std::vector<DbObject> object_list;

    for(const auto& obj : result)

        object_list.push_back(obj);

    tran.commit();


    //load section, print size, first and last byte of array

    // short array (less than 256) - 's' first, 't' last

    //long array (over 256) - should be 'a' first, 'z' last, but it's not the case

    auto load_section_func = [&connection](DbObject& b){

        odb::transaction tran(connection.begin());

        connection.load(b, b.extras_);

        qDebug()<<b.content.size()<<b.content[0]<<b.content[b.content.size()-1];

        tran.commit();

    };


    for(auto& b: object_list)

        load_section_func(b);

}


void erase(DbObject& obj1, DbObject& obj2)

{

    odb::pgsql::database connection(//database connection details);

    odb::transaction tran(connection.begin());

    connection.erase(obj1);

    connection.erase(obj2);

    tran.commit();

}


int main(int, char*[])

{

        DbObject short_object;

        DbObject long_object;

        short_object.content = "short object content";// 's' first, 't' last

        long_object.content.resize(257);

        long_object.content[0] = 'a';

        long_object.content[long_object.content.size()-1] = 'z';// 'a' first, 'z' last


        persist(short_object, long_object);

        read();

        erase(short_object, long_object);

        return 0;

}

Another observation is that if we modify the above code to use a single database instance throughout the "persist - read - erase" cycle then the section is loaded as expected.