使用Slick for postgres增加列值

Question

I need to add 1 to column value for a record in postgres table based on some filter. Suppose I have two fields id and count and I want to increment count value by 1.

So far I have

MyTable.filter(_.id === someId).map(_.count).update(??)

Not sure how if it is possible to use update to do so. Any suggestion?

Answer 1

Currently, this is not supported in Slick - https://github.com/slick/slick/issues/497 . You could:

1. Use a plain SQL query; or
2. Retrieve the current "count" value in a separate query, increment, then do the update, using the transactionally modifier to force the use of one transaction. Though, depending on the level of transaction isolation in your database, the use of a transaction might not be enough to avoid race conditions.