Recursive Tree View Query Using Slick

Question

Recursive Tree View Query Using Slick

My table data forms a tree structure where one row can refer to the parent row in the same table.

What I'm trying to achieve using Slick is to write a query that will return a string and all its children. In addition, I would like to do the same, but write a request that will return the child and all his ancestors.

In other words:

findDown(1) must return

List(Group(1, 0, "1"), Group(3, 1, "3 (Child of 1)"))

findUp(5) must return

List(Group(5, 2, "5 (Child of 2)"), Group(2, 0, "2"))

Here is a full-featured worksheet (with the exception of missing solutions ;-).

package com.exp.worksheets

import scala.slick.driver.H2Driver.simple._

object ParentChildTreeLookup {

  implicit val session = Database.forURL("jdbc:h2:mem:test1;", driver = "org.h2.Driver").createSession()

  session.withTransaction {
    Groups.ddl.create
  }

  Groups.insertAll(
    Group(1, 0, "1"),
    Group(2, 0, "2"),
    Group(3, 1, "3 (Child of 1)"),
    Group(4, 3, "4 (Child of 3)"),
    Group(5, 2, "5 (Child of 2)"),
    Group(6, 2, "6 (Child of 2)"))

  case class Group(
    id: Long = -1,
    id_parent: Long = -1,
    label: String = "")

  object Groups extends Table[Group]("GROUPS") {
    def id = column[Long]("ID", O.PrimaryKey, O.AutoInc)
    def id_parent = column[Long]("ID_PARENT")
    def label = column[String]("LABEL")
    def * = id ~ id_parent ~ label <> (Group, Group.unapply _)
    def autoInc = id_parent ~ label returning id into {
      case ((_, _), id) => id
    }

    def findDown(groupId: Long)(implicit session: Session) = { ??? }

    def findUp(groupId: Long)(implicit session: Session) = { ??? }
  }

}

Very bad, and a static try in findDowncould be something like this:

private def groupsById = for {
  group_id <- Parameters[Long]
  g <- Groups; if g.id === group_id
} yield g

private def childrenByParentId = for {
  parent_id <- Parameters[Long]
  g <- Groups; if g.id_parent === parent_id
} yield g


def findDown(groupId: Long)(implicit session: Session) = { groupsById(groupId).list union childrenByParentId(groupId).list }

Slick , id id_parent. . , .

+5

scala slick

Jack 25 . '13 15:38

2

hohonuuli · Answer 1 · 2013-03-15T23:05:01+0000

SQL slick. SQL ( SQL Server):

WITH org_name AS 
(
    SELECT DISTINCT
        parent.id AS parent_id,
        parentname.label as parent_label,
        child.id AS child_id,
        childname.ConceptName as child_label
    FROM
        Group parent RIGHT OUTER JOIN 
        Group child ON child.parent_id = parent.id
), 
jn AS 
(   
    SELECT
        parent_id,
        parent_label,
        child_id,
        child_label
    FROM
        org_name 
    WHERE
        parent_id = 5
    UNION ALL 
        SELECT
            C.parent_id,
            C.parent_label,
            C.child_id,
            C.child_label 
        FROM
            jn AS p JOIN 
            org_name AS C ON C.child_id = p.parent_id
) 
SELECT DISTINCT
    jn.parent_id,
    jn.parent_label,
    jn.child_id,
    jn.child_label
FROM
    jn 
ORDER BY
    1;

, :

org_name AS C ON C.child_id = p.parent_id

org_name AS C ON C.parent_id = p.child_id

EECOLOR · Answer 2 · 2013-02-25T16:29:00+0000

SQL . :

().
, ( SQL ) .

, SQL, Slick. Leaky Abstractions .

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Slick, , , . NoSQL .

Recursive Tree View Query Using Slick

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