3.0: Is it wise to ask for write access when all you want to do is make a request?

[servoz]

In populse_db.storage_api.StorageFileAPI.primary_key(), we have:

dbs = self._get_database_session(connection_id, write=True)

The code is poorly documented, so I may misunderstand it, but it seems that write=True is usually reserved for writing operations in a database. However, in this case, it is just a request to retrieve the primary key of a collection (perhaps this is where I am mistaken?).

So, if we do something like:

with self.project.database.data() as database_data:
    foo = database_data.get_primary_key_name(COLLECTION_CURRENT)

we encounter the following error:

File "/data/Git_Projects/populse_db/python/populse_db/storage.py", line 290, in primary_key
    return self._storage_api.primary_key(self._connection_id, self._path)
  File "/data/Git_Projects/populse_db/python/populse_db/storage_api.py", line 369, in primary_key
    dbs = self._get_database_session(connection_id, write=True)
  File "/data/Git_Projects/populse_db/python/populse_db/storage_api.py", line 176, in _get_database_session
    raise PermissionError(self._read_only_error)
PermissionError: database is read-only

To fix this, we can use:

with self.project.database.data(write=True) as database_data:
    foo = database_data.get_primary_key_name(COLLECTION_CURRENT)

However, this seems strange for a simple database query.

The get_primary_key_name method belongs to populse_mia.data_manager.database_mia.DatabaseMiaData. It uses:

`self.storage_data[collection_name].primary_key()[0]

Another possible fix would be to replace it with:

next(iter(self.storage_data[collection_name].keys()))

This seems to work, but it would be better to use a dedicated method from populse_db, such as populse_db.storage_api.StorageFileAPI.primary_key().
Additionally, are we sure that the primary key is always the first element in the dbs[collection].keys() dictionary?

So, I have a few ways to fix this issue, but none seem entirely clean.
Ideally, the following should work:

with self.project.database.data() as database_data:
    foo = database_data.get_primary_key_name(COLLECTION_CURRENT)

It also seems that write=True is used very frequently (too frequently?) in populse_db.storage_api.StorageFileAPI.
For instance, could we consider modifying database session access in StorageFileAPI to omit write=True when we only need to make a read request and do not require indexing?
For example, in populse_db.storage_api.StorageFileAPI.primary_key(), by using:

dbs = self._get_database_session(connection_id, write=False)

instead?

[sapetnioc]

Sorry for the late answer,. You are right, write=True is required only when a write access is going to be done during the session. If there is only read access, it should not be used in user code and must not be used in populse_db code.

[servoz]

Thank you very much @sapetnioc . I can now make the changes correctly on Mia's side.