2017-01-28 第十八回 #渋谷java I introduce you to the dynamic SQL in doobie, which is one of new for version 0.4.0.

1. Statement Fragments
- How to write dynamic SQL queries in doobie -
2017-01-28
第十八回 #渋谷java

2. 0.4.0 release!
● Cats Support
● Simple statement logging Support
● Changes to Add-On Modules
● Dynamic SQL

3. 0.4.0 release!
● Cats Support
● Simple statement logging Support
● Changes to Add-On Modules
● Dynamic SQL

4. The dynamic SQL story
The dynamic SQL story is now slightly better with
the introduction of composable statement
fragments.
"Changes to Core". changelog.
https://github.com/tpolecat/doobie/blob/series/0.4.x/CHANGELOG.md#changes-to-core, (参照 2017-01-25)

5. The dynamic SQL story
The dynamic SQL story is now slightly better with
the introduction of composable statement
fragments.
"Changes to Core". changelog.
https://github.com/tpolecat/doobie/blob/series/0.4.x/CHANGELOG.md#changes-to-core, (参照 2017-01-25)
若干改善された

6. Setting Up
import doobie.imports._
import scalaz._, Scalaz._, concurrent.Task
val xa = DriverManagerTransactor[Task](
"org.h2.Driver", "url", "user", "password"
)
// YOLO mode
import xa.yolo._

7. SQL literals
val select = fr"select * from user"
val where = fr"where uid = $id"
val sql = select ++ where
sql.query[User].quick.unsafePerformSync

8. SQL literals
val select: Fragment = fr"select * from user"
val where: Fragment = fr"where uid = $id"
val sql: Fragment = select ++ where
sql.query[User].quick.unsafePerformSync
sqlの代わりにfrで定義

9. SQL literals
val select: Fragment = fr"select * from user"
val where: Fragment = fr"where uid = $id"
val sql: Fragment = select ++ where
sql.query[User].quick.unsafePerformSync
++で連結

10. An arbitrary string value
val table = "user"
val select = fr"select * from"
val sql = select ++ Fragment.const(table)
sql.query[Unit].sql
// "select * from user"

11. An arbitrary string value
val table = "user"
val select = fr"select * from"
val sql = select ++ Fragment.const(table)
sql.query[Unit].sql
// "select * from user"
SQLパラメータではないもの

12. The Fragments Module
● some convenience combinators
○ andOpt
○ orOpt
○ whereAndOpt
○ whereOrOpt
○ in
and so on

13. The Fragments Module - whereAndOpt
import Fragments._
val uid: Option[Int] = ...
val json: Option[String] = ...
val sql = fr"select * from user" ++
whereAndOpt(
uid.map(p => fr"uid = $p"), // Option[Fragment]
json.map(p => fr"json like $p") // Option[Fragment]
)

14. The Fragments Module - whereAndOpt
import Fragments._
val uid: Option[Int] = None
val json: Option[String] = None
val sql = fr"select * from user" ++
whereAndOpt(
uid.map(p => fr"uid = $p"), // Option[Fragment]
json.map(p => fr"json like $p") // Option[Fragment]
)
// "select * from user "

15. The Fragments Module - whereAndOpt
import Fragments._
val uid: Option[Int] = Some(1)
val json: Option[String] = None
val sql = fr"select * from user" ++
whereAndOpt(
uid.map(p => fr"uid = $p"), // Option[Fragment]
json.map(p => fr"json like $p") // Option[Fragment]
)
// "select * from user WHERE uid = ? "

16. The Fragments Module - whereAndOpt
import Fragments._
val uid: Option[Int] = Some(1)
val json: Option[String] = Some("%foo%")
val sql = fr"select * from user" ++
whereAndOpt(
uid.map(p => fr"uid = $p"), // Option[Fragment]
json.map(p => fr"json like $p") // Option[Fragment]
)
// "select * from user WHERE uid = ? AND json like ? "

17. The Fragments Module - in
import Fragments._
val uids: List[Int] = ...
val sql = fr"select * from user" ++
whereAndOpt(
uids.toNel.map(p => in(fr"uid", p))// Option[Fragment]
)
Option[NonEmptyList[Int]]

18. The Fragments Module - in
import Fragments._
val uids: List[Int] = Nil
val sql = fr"select * from user" ++
whereAndOpt(
uids.toNel.map(p => in(fr"uid", p))// Option[Fragment]
)
// "select * from user "

19. The Fragments Module - in
import Fragments._
val uids: List[Int] = List(1,10)
val sql = fr"select * from user" ++
whereAndOpt(
uids.toNel.map(p => in(fr"uid", p))// Option[Fragment]
)
// "select * from user WHERE uid IN (?, ?) "

20. Conclusion
● 嬉しいこと
○ dynamic SQL が書けるようになった
○ 特にwhere句の組み立ては高確率で必要になる
● 悲しいこと
○ 「若干」感
○ 使い方がよくわからないもの（andOpt）
まだ0.4.xなのでこれからの進化に期待！