CODEWITHSUNDEEP
haskellyesodpersistent
iamnat
iamnat

Reputation: 4166

Select with list of keys Persistent (Yesod)

I need to fetch a list of entities from a list of keys, with Persistent (Yesod)

Say I have a Model and its corresponding ModelId. I have with me:

keys :: [ModelId]

and I need to get

models :: [Model]

The current best way of doing that seems to be:

models' <- mapM get keys
models <- return $ Data.Maybe.catMaybes models'

Is there a more efficient way of doing this? Does persistent queue up the fetch requests or execute them one by one?

There's the same question at yesod persistent: get list of entities from list of keys but I would like to know whether this is the most efficient way of doing this.

Upvotes: 3

Views: 573

Answers (1)

ms.
ms.

Reputation: 332

If I understood your question well, you can achieve it by trying something like this:

models' <- selectList [ModelId <-. keys] []

By using mapM you will query the database length keys times, while selectList performs a single query.

Upvotes: 3

Related Questions