eids -are they every reused in a tdb

Phuket2

Firstly sorry, if this documented. I could not find the answer in the docs.
Q. Once a record is assigned an eid, will that eid ever change or be reissued if the record is deleted?

I did a simple class that subclasses list, and using tdb for the lists persistence. So on a save, I search for a key, if I don't find it I do a db.insert, otherwise I do a db.update.
In this simple case it would make sense to save the eid. Eg, if it was 0, then I would have to do an insert then save the eid and use it do do my updates rather than searching each time.

I am assuming eid's would be duplicated in different tables inside a tdb. I just assert that, because maybe they are not.

Thanks in advance...
Btw, nice interview on Talk Python To Me

msiemens

Hey @Phuket2 ,

right now there are no official guarantees whether or not EIDs are reused as I consider the ID scheme to be an implementation detail. But as of now, EIDs are not reused within a table. Also, EIDs are unique within a table only, so with multiple tables there likely will be entries in different tables but with the same EID.

Cheers!
Markus

Phuket2

msiemens , ok thanks. I am guessing your statement is related to middleware and storage extensions. Well, that's what makes sense to me. But may not be true.

But i still think its a powerful statement if you could for example say. If you are not using middleware or alternative storage methods the EID will never be reused for a given table, unless the table is purged for example.
Just can give some certainty if you decide to cache eids in some way.

Just an idea

msiemens

Phuket2
But i still think its a powerful statement if you could for example say. If you are not using middleware or alternative storage methods the EID will never be reused for a given table, unless the table is purged for example.

Right now EIDs are determined by TinyDB itself, not by middlewares or storage methods. The database instance looks at what EIDs are in use currently and then determines which the next EID is going to be.

Phuket2 Just can give some certainty if you decide to cache eids in some way.

Right now, TinyDB uses numbers for EIDs which are incremented with every new item. Let's say, you delete the item with the hightest EID and close and re-open the database. Now to make sure it doesn't reuse EIDs, TinyDB would have to remember it deleted this item and not use this EID again. With the current design there's no elegant way to do this. This basically means that if you delete an item with the highest EID, its EID will probably be reused if you reopen the database. It may not be great that EIDs will be reused with that behavior, but it makes the implementation of TinyDB a lot simpler as it doesn't have to remember which EIDs have been deleted.

I hope that clears it up a little.

Cheers!

Phuket2

msiemens
Ok, I see and understand. Thanks again for the info.