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The one line per minute was observed when trying to compile a query over an HList backed record with more than 300 columns. The problem was a polynomial increase of the size of the implicit search tree. This is due to the way implicits are used in shapeless HList library. Slick has a different approach which is much faster, but slightly less general.

The gist is that once you have [edit: recursive] typeclasses or implicits your search can become arbitrarily large and slow. There's nothing that can be done about it by the compiler except arbitrarily pruning the search tree. Or otherwise put, you should factor in implicit search complexity when designing your libraries.




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