Created
March 27, 2018 10:22
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Slick support for dynamic sort with pagination
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| import slick.lifted.Rep | |
| import slick.ast.Ordering.Direction | |
| import slick.ast.Ordering | |
| import slick.lifted.Query | |
| import slick.lifted.ColumnOrdered | |
| import slick.lifted.Ordered | |
| import scala.util.control.NoStackTrace | |
| case class PageRequest(offset: Int, | |
| limit: Int, | |
| sort: Vector[(String, Direction)]) | |
| // Based off https://stackoverflow.com/questions/42383842/dynamic-order-by-in-scala-slick-with-several-columns | |
| object DynamicSortBySupport { | |
| case class InvalidSort(invalidField: String) | |
| extends Exception with NoStackTrace | |
| trait HasSortColumns { | |
| /** The runtime map between string names and table columns */ | |
| val sortColumns: Map[String, Rep[_]] | |
| } | |
| implicit class MultiSortableQuery[E <: HasSortColumns, U, C[_]]( | |
| query: Query[E, U, C]) { | |
| /** Sorts the query by multiple columns in order. Invalid sort names are skipped */ | |
| def dynamicSortBy(sortBy: Seq[(String, Direction)]) | |
| : Either[InvalidSort, Query[E, U, C]] = { | |
| val zero: Either[InvalidSort, Query[E, U, C]] = Right(query) | |
| sortBy.foldRight(zero) { | |
| // foldRight specifically because stacking sortBy invocations on a query operates in reverse order, | |
| // so the reversed order of a right fold means the final result is in the desired order. | |
| case (_, err @ Left(_)) => err | |
| case ((sortColumn, sortOrder), Right(queryToSort)) => | |
| val sortOrderRep: Rep[_] => Ordered = | |
| ColumnOrdered(_, Ordering(sortOrder)) | |
| val sortColumnRep: E => Rep[_] = | |
| _.sortColumns.getOrElse(sortColumn, throw InvalidSort(sortColumn)) | |
| try { | |
| Right(queryToSort.sortBy(sortColumnRep)(sortOrderRep)) | |
| } catch { | |
| case ex: InvalidSort => Left(ex) | |
| } | |
| } | |
| } | |
| def paginated(paging: PageRequest): Either[InvalidSort, Query[E, U, C]] = | |
| dynamicSortBy(paging.sort).map(q => | |
| q.drop(paging.offset).take(paging.limit)) | |
| } | |
| } |
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