CODEWITHSUNDEEP
sqlhaskell
elfeck
elfeck

Reputation: 385

Get multiple persistent entries by keylist

I use SQLite with persistent in Haskell.

I have a list of keys i.e. [PostId]. Now I want to get all entries
[Desc PostCrtDate, OffsetBy from, LimitTo (to - from + 1)].

Is there an alternative to selectList but with a list of keys instead of or in addition to the "normal" conditions of a SQL query?

It seems horribly inefficient to use mapM get keyList and then do sorting/offsetting/limiting, especially with a big database.

I am open to using esqueleto if necessary but I would rather not introduce another dependency.

Thanks!

Upvotes: 2

Views: 68

Answers (1)

Michael Snoyman
Michael Snoyman

Reputation: 31355

I'm on a mobile right now and therefore may get the syntax wrong, but it's something like:

selectWhere [PostId <-. IdList] []

That operator is the "in" operator, checking if a value is in a list.

Note that this will not give any errors if some of the keys are not found, you'd need to check for that manually.

Upvotes: 3

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