Scala Slick，如何仅在不存在时创建模式
Scala Slick, how to create Schema ONLY if it does not exist
在 Scala Slick 中，可以使用以下内容创建数据库模式：
val schema = coffees.schema ++ suppliers.schema
db.run(DBIO.seq(
schema.create
))
从本文档页面的底部开始http://slick.typesafe.com/doc/3.0.0/schemas.html
但是，如果数据库模式已经存在，则会引发异常。
当且仅当它不存在时，是否有正常或正确的方法来创建模式？
为什么不简单地检查 create 之前是否存在？
val schema = coffees.schema ++ suppliers.schema
db.run(DBIO.seq(
if (!MTable.getTables.list.exists(_.name.name == MyTable.tableName)){
schema.create
}
))
在 Slick 3.0 中，Mtable.getTables 是一个 DBAction，所以像这样的东西可以工作：
val coffees = TableQuery[Coffees]
try {
Await.result(db.run(DBIO.seq(
MTable.getTables map (tables => {
if (!tables.exists(_.name.name == coffees.baseTableRow.tableName))
coffees.schema.create
})
)), Duration.Inf)
} finally db.close
与 points out about the 一样，table没有创建。我设法通过稍微修改第一个答案的代码使其工作：
val coffees = TableQuery[Coffees]
try {
def createTableIfNotInTables(tables: Vector[MTable]): Future[Unit] = {
if (!tables.exists(_.name.name == events.baseTableRow.tableName)) {
db.run(coffees.schema.create)
} else {
Future()
}
}
val createTableIfNotExist: Future[Unit] = db.run(MTable.getTables).flatMap(createTableIfNotInTables)
Await.result(createTableIfNotExist, Duration.Inf)
} finally db.close
使用以下导入：
import slick.jdbc.meta.MTable
import slick.driver.SQLiteDriver.api._
import scala.concurrent.{Await, Future}
import scala.concurrent.duration.Duration
import scala.concurrent.ExecutionContext.Implicits.global
这就是我使用 slick 3.1.1 和 Postgres 对多个表所做的
import slick.driver.PostgresDriver.api._
import slick.jdbc.meta.MTable
import scala.concurrent.Await
import scala.concurrent.duration.Duration
import scala.concurrent.ExecutionContext.Implicits.global
val t1 = TableQuery[Table1]
val t2 = TableQuery[Table2]
val t3 = TableQuery[Table3]
val tables = List(t1, t2, t3)
val existing = db.run(MTable.getTables)
val f = existing.flatMap( v => {
val names = v.map(mt => mt.name.name)
val createIfNotExist = tables.filter( table =>
(!names.contains(table.baseTableRow.tableName))).map(_.schema.create)
db.run(DBIO.sequence(createIfNotExist))
})
Await.result(f, Duration.Inf)
在 Slick 3.3.0 中添加了 createIfNotExists 和 dropIfExists 模式方法。所以：
db.run(coffees.schema.createIfNotExists)
用谷歌搜索这个问题，并根据答案尝试了几种解决方案，直到弄明白。
不能在由 3 个 table 组成的架构上使用 createIfNotExists，其中一个 table 具有复合主键。这里，第 3 个 table 有一个主键，由第 1 个和第 2 个 table 中的每一个的主键组成。第二次遇到 .createIfNotExists 时，此模式出现错误。我在 scala 2.12.8 上使用 slick 3.3.1。
class UserTable(tag: Tag) extends Table[User](tag, "user") {
def id = column[Long]("id", O.AutoInc, O.PrimaryKey)
def name = column[String]("name")
def email = column[Option[String]]("email")
def * = (id.?, name, email).mapTo[User]
}
val users = TableQuery[UserTable]
lazy val insertUser = users returning users.map(_.id)
case class Room(title: String, id: Long = 0L)
class RoomTable(tag: Tag) extends Table[Room](tag, "room") {
def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
def title = column[String]("title")
def * = (title, id).mapTo[Room]
}
val rooms = TableQuery[RoomTable]
lazy val insertRoom = rooms returning rooms.map(_.id)
case class Occupant(roomId: Long, userId: Long)
class OccupantTable(tag: Tag) extends Table[Occupant](tag, "occupant") {
def roomId = column[Long]("room")
def userId = column[Long]("user")
def pk = primaryKey("room_user_pk", (roomId, userId) )
def * = (roomId, userId).mapTo[Occupant]
}
val occupants = TableQuery[OccupantTable]
首先我可以成功创建模式并添加用户、房间和居住者。在如下所示第二次使用 .createIfNotExists 时，出现重复主键错误：
println("\n2nd run on .createIfNotExists using different values for users, rooms and occupants")
val initdup = for {
_ <- users.schema.createIfNotExists
_ <- rooms.schema.createIfNotExists
_ <- occupants.schema.createIfNotExists
curlyId <- insertUser += User(None, "Curly", Some("curly@example.org"))
larryId <- insertUser += User(None, "Larry")
moeId <- insertUser += User(None, "Moe", Some("moe@example.org"))
shedId <- insertRoom += Room("Shed")
_ <- occupants += Occupant(shedId, curlyId)
_ <- occupants += Occupant(shedId, moeId)
} yield ()
异常情况如下：
2nd run on .createIfNotExists using different values for users, rooms and occupants
[error] (run-main-2) org.h2.jdbc.JdbcSQLException: Constraint "room_user_pk" already exists; SQL statement:
[error] alter table "occupant" add constraint "room_user_pk" primary key("room","user") [90045-197]
[error] org.h2.jdbc.JdbcSQLException: Constraint "room_user_pk" already exists; SQL statement:
[error] alter table "occupant" add constraint "room_user_pk" primary key("room","user") [90045-197]
[error] at org.h2.message.DbException.getJdbcSQLException(DbException.java:357)
[error] at org.h2.message.DbException.get(DbException.java:179)
[error] at org.h2.message.DbException.get(DbException.java:155)
[error] at org.h2.command.ddl.AlterTableAddConstraint.tryUpdate(AlterTableAddConstraint.java:110)
[error] at org.h2.command.ddl.AlterTableAddConstraint.update(AlterTableAddConstraint.java:78)
[error] at org.h2.command.CommandContainer.update(CommandContainer.java:102)
[error] at org.h2.command.Command.executeUpdate(Command.java:261)
[error] at org.h2.jdbc.JdbcPreparedStatement.execute(JdbcPreparedStatement.java:249)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run$adapted(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcBackend$SessionDef.withPreparedStatement(JdbcBackend.scala:425)
[error] at slick.jdbc.JdbcBackend$SessionDef.withPreparedStatement$(JdbcBackend.scala:420)
[error] at slick.jdbc.JdbcBackend$BaseSession.withPreparedStatement(JdbcBackend.scala:489)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run$adapted(JdbcActionComponent.scala:292)
[error] at scala.collection.Iterator.foreach(Iterator.scala:941)
[error] at scala.collection.Iterator.foreach$(Iterator.scala:941)
[error] at scala.collection.AbstractIterator.foreach(Iterator.scala:1429)
[error] at scala.collection.IterableLike.foreach(IterableLike.scala:74)
[error] at scala.collection.IterableLike.foreach$(IterableLike.scala:73)
[error] at scala.collection.AbstractIterable.foreach(Iterable.scala:56)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.run(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.run(JdbcActionComponent.scala:290)
[error] at slick.jdbc.JdbcActionComponent$SimpleJdbcProfileAction.run(JdbcActionComponent.scala:28)
[error] at slick.jdbc.JdbcActionComponent$SimpleJdbcProfileAction.run(JdbcActionComponent.scala:25)
[error] at slick.basic.BasicBackend$DatabaseDef$$anon.liftedTree1(BasicBackend.scala:276)
[error] at slick.basic.BasicBackend$DatabaseDef$$anon.run(BasicBackend.scala:276)
[error] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] at java.lang.Thread.run(Thread.java:748)
[error] Nonzero exit code: 1
[error] (Compile / run) Nonzero exit code: 1
此外，我可以在所有 table 都是按照 O.PrimaryKey 约定创建的架构上多次使用 .createIfNotExists。
我可以做一些按摩代码吗？是否有解决方法，使 .createIfNotExists 仍可用于复合主键案例？
在 Scala Slick 中，可以使用以下内容创建数据库模式：
val schema = coffees.schema ++ suppliers.schema
db.run(DBIO.seq(
schema.create
))
从本文档页面的底部开始http://slick.typesafe.com/doc/3.0.0/schemas.html
但是，如果数据库模式已经存在，则会引发异常。
当且仅当它不存在时，是否有正常或正确的方法来创建模式？
为什么不简单地检查 create 之前是否存在？
val schema = coffees.schema ++ suppliers.schema
db.run(DBIO.seq(
if (!MTable.getTables.list.exists(_.name.name == MyTable.tableName)){
schema.create
}
))
在 Slick 3.0 中，Mtable.getTables 是一个 DBAction，所以像这样的东西可以工作：
val coffees = TableQuery[Coffees]
try {
Await.result(db.run(DBIO.seq(
MTable.getTables map (tables => {
if (!tables.exists(_.name.name == coffees.baseTableRow.tableName))
coffees.schema.create
})
)), Duration.Inf)
} finally db.close
与
val coffees = TableQuery[Coffees]
try {
def createTableIfNotInTables(tables: Vector[MTable]): Future[Unit] = {
if (!tables.exists(_.name.name == events.baseTableRow.tableName)) {
db.run(coffees.schema.create)
} else {
Future()
}
}
val createTableIfNotExist: Future[Unit] = db.run(MTable.getTables).flatMap(createTableIfNotInTables)
Await.result(createTableIfNotExist, Duration.Inf)
} finally db.close
使用以下导入：
import slick.jdbc.meta.MTable
import slick.driver.SQLiteDriver.api._
import scala.concurrent.{Await, Future}
import scala.concurrent.duration.Duration
import scala.concurrent.ExecutionContext.Implicits.global
这就是我使用 slick 3.1.1 和 Postgres 对多个表所做的
import slick.driver.PostgresDriver.api._
import slick.jdbc.meta.MTable
import scala.concurrent.Await
import scala.concurrent.duration.Duration
import scala.concurrent.ExecutionContext.Implicits.global
val t1 = TableQuery[Table1]
val t2 = TableQuery[Table2]
val t3 = TableQuery[Table3]
val tables = List(t1, t2, t3)
val existing = db.run(MTable.getTables)
val f = existing.flatMap( v => {
val names = v.map(mt => mt.name.name)
val createIfNotExist = tables.filter( table =>
(!names.contains(table.baseTableRow.tableName))).map(_.schema.create)
db.run(DBIO.sequence(createIfNotExist))
})
Await.result(f, Duration.Inf)
在 Slick 3.3.0 中添加了 createIfNotExists 和 dropIfExists 模式方法。所以：
db.run(coffees.schema.createIfNotExists)
用谷歌搜索这个问题，并根据答案尝试了几种解决方案，直到弄明白。
不能在由 3 个 table 组成的架构上使用 createIfNotExists，其中一个 table 具有复合主键。这里，第 3 个 table 有一个主键，由第 1 个和第 2 个 table 中的每一个的主键组成。第二次遇到 .createIfNotExists 时，此模式出现错误。我在 scala 2.12.8 上使用 slick 3.3.1。
class UserTable(tag: Tag) extends Table[User](tag, "user") {
def id = column[Long]("id", O.AutoInc, O.PrimaryKey)
def name = column[String]("name")
def email = column[Option[String]]("email")
def * = (id.?, name, email).mapTo[User]
}
val users = TableQuery[UserTable]
lazy val insertUser = users returning users.map(_.id)
case class Room(title: String, id: Long = 0L)
class RoomTable(tag: Tag) extends Table[Room](tag, "room") {
def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
def title = column[String]("title")
def * = (title, id).mapTo[Room]
}
val rooms = TableQuery[RoomTable]
lazy val insertRoom = rooms returning rooms.map(_.id)
case class Occupant(roomId: Long, userId: Long)
class OccupantTable(tag: Tag) extends Table[Occupant](tag, "occupant") {
def roomId = column[Long]("room")
def userId = column[Long]("user")
def pk = primaryKey("room_user_pk", (roomId, userId) )
def * = (roomId, userId).mapTo[Occupant]
}
val occupants = TableQuery[OccupantTable]
首先我可以成功创建模式并添加用户、房间和居住者。在如下所示第二次使用 .createIfNotExists 时，出现重复主键错误：
println("\n2nd run on .createIfNotExists using different values for users, rooms and occupants")
val initdup = for {
_ <- users.schema.createIfNotExists
_ <- rooms.schema.createIfNotExists
_ <- occupants.schema.createIfNotExists
curlyId <- insertUser += User(None, "Curly", Some("curly@example.org"))
larryId <- insertUser += User(None, "Larry")
moeId <- insertUser += User(None, "Moe", Some("moe@example.org"))
shedId <- insertRoom += Room("Shed")
_ <- occupants += Occupant(shedId, curlyId)
_ <- occupants += Occupant(shedId, moeId)
} yield ()
异常情况如下：
2nd run on .createIfNotExists using different values for users, rooms and occupants
[error] (run-main-2) org.h2.jdbc.JdbcSQLException: Constraint "room_user_pk" already exists; SQL statement:
[error] alter table "occupant" add constraint "room_user_pk" primary key("room","user") [90045-197]
[error] org.h2.jdbc.JdbcSQLException: Constraint "room_user_pk" already exists; SQL statement:
[error] alter table "occupant" add constraint "room_user_pk" primary key("room","user") [90045-197]
[error] at org.h2.message.DbException.getJdbcSQLException(DbException.java:357)
[error] at org.h2.message.DbException.get(DbException.java:179)
[error] at org.h2.message.DbException.get(DbException.java:155)
[error] at org.h2.command.ddl.AlterTableAddConstraint.tryUpdate(AlterTableAddConstraint.java:110)
[error] at org.h2.command.ddl.AlterTableAddConstraint.update(AlterTableAddConstraint.java:78)
[error] at org.h2.command.CommandContainer.update(CommandContainer.java:102)
[error] at org.h2.command.Command.executeUpdate(Command.java:261)
[error] at org.h2.jdbc.JdbcPreparedStatement.execute(JdbcPreparedStatement.java:249)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run$adapted(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcBackend$SessionDef.withPreparedStatement(JdbcBackend.scala:425)
[error] at slick.jdbc.JdbcBackend$SessionDef.withPreparedStatement$(JdbcBackend.scala:420)
[error] at slick.jdbc.JdbcBackend$BaseSession.withPreparedStatement(JdbcBackend.scala:489)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.$anonfun$run$adapted(JdbcActionComponent.scala:292)
[error] at scala.collection.Iterator.foreach(Iterator.scala:941)
[error] at scala.collection.Iterator.foreach$(Iterator.scala:941)
[error] at scala.collection.AbstractIterator.foreach(Iterator.scala:1429)
[error] at scala.collection.IterableLike.foreach(IterableLike.scala:74)
[error] at scala.collection.IterableLike.foreach$(IterableLike.scala:73)
[error] at scala.collection.AbstractIterable.foreach(Iterable.scala:56)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.run(JdbcActionComponent.scala:292)
[error] at slick.jdbc.JdbcActionComponent$SchemaActionExtensionMethodsImpl$$anon.run(JdbcActionComponent.scala:290)
[error] at slick.jdbc.JdbcActionComponent$SimpleJdbcProfileAction.run(JdbcActionComponent.scala:28)
[error] at slick.jdbc.JdbcActionComponent$SimpleJdbcProfileAction.run(JdbcActionComponent.scala:25)
[error] at slick.basic.BasicBackend$DatabaseDef$$anon.liftedTree1(BasicBackend.scala:276)
[error] at slick.basic.BasicBackend$DatabaseDef$$anon.run(BasicBackend.scala:276)
[error] at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
[error] at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
[error] at java.lang.Thread.run(Thread.java:748)
[error] Nonzero exit code: 1
[error] (Compile / run) Nonzero exit code: 1
此外，我可以在所有 table 都是按照 O.PrimaryKey 约定创建的架构上多次使用 .createIfNotExists。
我可以做一些按摩代码吗？是否有解决方法，使 .createIfNotExists 仍可用于复合主键案例？