Re: drop/createTables

[Jeremy Lainé]

Hi,

Your point is completely valid, please open an issue on github to track it.

Jeremy

On 17 Jul 2014 13:12, otop...@gmail.com wrote:

I am using: qdjango v0.4.0-158-g810b021, mysql 5.5.37 on 64bit Linux

I am having problems creating/droping tables from database with functions QDjango::createTables(); and QDjango::dropTables();
It seems that those functions create tables in alphabetical order - it does not care for FK dependencies.

If I have table A which has foreign key to table B:

SQL query "CREATE TABLE `A` (`id` integer `B_id` integer NOT NULL, CONSTRAINT `FK_B_id` FOREIGN KEY (`B_id`) REFERENCES `B` (`id`) ON DELETE RESTRICT)"

Then it ends with error like

SQL error QSqlError("1005", "QMYSQL: Unable to execute query", "Can't create table 'DB.A' (errno: 150)")

There is workaround - to run createTables many times (or until there is no error 150).

It would be nice if the createTables() checked for foreign keys first,
from these FK dependencies created list of tables in right order and then created those tables.

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[otop...@gmail.com]

Is there a way to create/drop just one table?

[Jeremy Lainé]

On 07/18/2014 10:35 AM, otop...@gmail.com wrote:
> Is there a way to create/drop just one table?
>

Yes absolutely:

QDjangoMetaModel metaModel = QDjango::registerModel<SomeModel>();
metaModel.createTable()
metaModel.dropTable()


Jeremy

[otop...@gmail.com]

Ok I found better solution for my problem.
I've modified createTables and dropTables to create and drop them in order of registration.
So I register tables in correct order and then they are created or dropped without error :)

In QDjango.cpp added global list of table names:

QList<QByteArray> globalModelOrder = QList<QByteArray>();

These are modified functions, dropTables must iterate in reverse order..

bool QDjango::createTables()
{
    bool ret = true;
    foreach (const QByteArray &name, globalModelOrder)
        if (!globalMetaModels[name].createTable())
            ret = false;
    return ret;
}

bool QDjango::dropTables()
{
    bool ret = true;
    QList<QByteArray>::iterator it = globalModelOrder.end();
    while (it != globalModelOrder.begin()) {
        --it;
        if (!globalMetaModels[*it].dropTable())
            ret = false;
    }
    return ret;
}

[otop...@gmail.com]

I forgot this is modified registerModel:

QDjangoMetaModel QDjango::registerModel(const QMetaObject *meta)
{
    const QByteArray name = meta->className();
    if (!globalMetaModels.contains(name))
    {
        globalMetaModels.insert(name, QDjangoMetaModel(meta));
        globalModelOrder.append(name);
    }
    return globalMetaModels[name];
}

[Jeremy Lainé]

This is not really a "better solution" since it requires the user to register his models in a specific order..

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