I'm writing a CRUD app using Slick, and I want my update queries to only update a specific set of columns and I use .map().update() for that.
I have a function that returns a tuple of fields that can be updated in my table definition (def writableFields). And I have a funciton that returns a tuple of values to write there extracted from a case class.
It works fine, but it's annoying to create a repo and write the whole update function for every table. I want to create a generic form of this function, and make my table and it's companion object to extend some trait. But I cannot come up with correct type definitions.
Slick expects output of map() to be somehow compatible with the output of update. And I don't know how to make a generic type for tuples.
Is it even possible to accomplish? Or is there an alternative way to limit code duplication? Ideally I want to avoid writing Repos at all and just either instantiate a generic class or call a generic method.
object ProjectsRepo extends BaseRepository[Projects, Project] {
protected val query = lifted.TableQuery[Projects]
def update(id: Long, c: Project): Future[Option[Project]] = {
val q = filterByIdQuery(id).map(_.writableFields)
.update(Projects.mapFormToTable(c))
(db run q).flatMap(
affected =>
if (affected > 0) {
findOneById(id)
} else {
Future(None)
}
)
}
}
class Projects(tag: Tag) extends Table[Project](tag, "projects") with IdentifiableTable[Long] {
val id = column[Long]("id", O.PrimaryKey, O.AutoInc)
val title = column[String]("title")
val slug = column[String]("slug")
val created_at = column[Timestamp]("created_at")
val updated_at = column[Timestamp]("updated_at")
def writableFields =
(
title,
slug
)
def readableFields =
(
id,
created_at,
updated_at
)
def allFields = writableFields ++ readableFields // shapeless
def * = allFields <> (Projects.mapFromTable, (_: Project) => None)
}
object Projects {
def mapFormToTable(c: Project): FormFields =
(
c.title,
c.slug
)
}
I would like to understand this error:
found : row.type (with underlying type _#TableElementType)
required: _1#TableElementType
Looks like I was very close, but what is this "1" in _1#TableElementType? Can I convert one in the other?
Edit: useful bits of codes for context (Play + Slick):
abstract class GenericDAO[T <: AbstractTable[_]](...) {
def table: TableQuery[T]
def insert(model: T#TableElementType) = db run (table += model)
}
trait TableObject[T <: AbstractTable[_]] {
def rowFromJson(jsObject: JsObject): T#TableElementType
def dao(driver: JdbcProfile, db: Database): GenericDAO[T]
}
// Controller Action with an instance implementing `tableObject` above:
val tableObject = tableObjectFactory("test")
val row = tableObject.rowFromJson(request.body.asJson.get)
val dao = tableObject.dao(driver, db) // tableObject has a DOA extending GenericDAO
dao.insert(row)
Example of tableObject:
object TestTable extends TableObject[Test] {
def dao(driver: JdbcProfile, db: Database) = new TestDAO(driver, db)
def rowFromJson(j: JsObject): TestRow = { TestRow(...) }
class TestDAO(...) extends GenericDAO[Test](driver, db) { ... }
}
I use a factory to get the right one from the url:
object TableObjectFactory {
def tableObjectFactory(name: String) = {
name match {
case "test" => TestTable
case "projects" => ProjectsTable
case "people" => PeopleTable
...
}
}
}
Although it doesn't explain much, it works if I make the DAO parse the request body and insert, instead of producing the row object separately and applying one of the DAO's methods on it.
I got all kinds of similar errors with names such as _$1#TableElementType, _1$u#TableElementType etc., but I think they are compiler aliases for different instances of the same class.
So the solution was to do
val j: JsValue = request.body.asJson.get
val tableObject: TableObject[_] = tableObjectFactory(table)
val dao = tableObject.dao(driver, db)
val res: Future[Int] = dao.insert(j)
where this new insert method now is abstract in GenericDAO, and in the concrete implementations takes a JsValue and parses it, then inserts:
class TestDAO(override val driver: JdbcProfile, override val db: Database) extends GenericDAO[Test](driver, db) {
import this.driver.api._
val table = TableQuery[Test]
//def insert(model: TestRow) = db run (table += model) // NO!
def insert(j: JsValue): Future[Int] = {
val row = TestRow(
(j \ "id").as[Int],
(j \ "name").as[String],
(j \ "value").as[Float],
(j \ "other").as[String]
)
db run (table += row)
}
}
At the same time, it makes Play forms completely useless, which is a good thing anyway.
I'm new to Slick. I'm creating a test suite for a Java application with Scala, ScalaTest and Slick. I'm using slick to prepare data before the test and to do assertions on the data after the test. The database used has some tables with more than 22 columns. I use slick-codegen to generate my schema code.
For tables with more than 22 columns, slick-codegen does not generate a case class, but a HList-based custom type and a companion ‘constructor’ method. As I understand it, this is because the limitation that tuples and case classes can only have 22 fields. The way the code is generated, the fields of a Row-object can only be accessed by index.
I have a couple of questions about this:
For what I understand, the 22 fields restriction for case classes is already fixed in Scala 2.11, right?
If that's the case, would it be possible to customize slick-codegen to generate case classes for all tables? I looked into this: I managed to set override def hlistEnabled = false in an overridden SourceCodeGenerator. But this results in Cannot generate tuple for > 22 columns, please set hlistEnable=true or override compound. So I don’t get the point of being able to disbale HList. May be the catch is in the ‘or override compound’ part, but I don't understand what that means.
Searching the internet on slick and 22 columns, I came across some solutions based on nested tuples. Would it be possible to customize the codegen to use this approach?
If generating code with case classes with > 22 fields is not a viable option, I think it would be possible to generate an ordinary class, which has an ‘accessor’ function for each column, thus providing a ‘mapping’ from index-based access to name-based access. I’d be happy to implement the generation for this myself, but I think I need some pointers where to start. I think it should be able to override the standard codegen for this. I already use an overridden SourceCodeGenerator for some custom data types. But apart from this use case, the documentation of the code generator does not help me that much.
I would really appreciate some help here. Thanks in advance!
I ended up further customizing slick-codegen. First, I'll answer my own questions, then I'll post my solution.
Answers to questions
The 22 arity limit might be lifted for case classes, it is not for tuples. And slick-codegen also generates some tuples, which I was not fully aware of when I asked the question.
Not relevant, see answer 1. (This might become relevant if the 22 arity limit gets lifted for tuples as well.)
I chose not to investigate this further, so this question remains unanswered for now.
This is the approach I took, eventually.
Solution: the generated code
So, I ended up generating "ordinary" classes for tables with more than 22 columns. Let me give an example of what I generate now. (Generator code follows below.) (This example has less than 22 columns, for brevity and readability reasons.)
case class BigAssTableRow(val id: Long, val name: String, val age: Option[Int] = None)
type BigAssTableRowList = HCons[Long,HCons[String,HCons[Option[Int]]], HNil]
object BigAssTableRow {
def apply(hList: BigAssTableRowList) = new BigAssTableRow(hlist.head, hList.tail.head, hList.tail.tail.head)
def unapply(row: BigAssTableRow) = Some(row.id :: row.name :: row.age)
}
implicit def GetResultBoekingenRow(implicit e0: GR[Long], e1: GR[String], e2: GR[Optional[Int]]) = GR{
prs => import prs._
BigAssTableRow.apply(<<[Long] :: <<[String] :: <<?[Int] :: HNil)
}
class BigAssTable(_tableTag: Tag) extends Table[BigAssTableRow](_tableTag, "big_ass") {
def * = id :: name :: age :: :: HNil <> (BigAssTableRow.apply, BigAssTableRow.unapply)
val id: Rep[Long] = column[Long]("id", O.PrimaryKey)
val name: Rep[String] = column[String]("name", O.Length(255,varying=true))
val age: Rep[Option[Int]] = column[Option[Int]]("age", O.Default(None))
}
lazy val BigAssTable = new TableQuery(tag => new BigAssTable(tag))
The hardest part was finding out how the * mapping works in Slick. There's not much documentation, but I found this Stackoverflow answer rather enlightening.
I created the BigAssTableRow object to make the use of HList transparent for the client code. Note that the apply function in the object overloads the apply from the case class. So I can still create entities by calling BigAssTableRow(id: 1L, name: "Foo"), while the * projection can still use the apply function that takes an HList.
So, I can now do things like this:
// I left out the driver import as well as the scala.concurrent imports
// for the Execution context.
val collection = TableQuery[BigAssTable]
val row = BigAssTableRow(id: 1L, name: "Qwerty") // Note that I leave out the optional age
Await.result(db.run(collection += row), Duration.Inf)
Await.result(db.run(collection.filter(_.id === 1L).result), Duration.Inf)
For this code it's totally transparent wether tuples or HLists are used under the hood.
Solution: how this is generated
I'll just post my entire generator code here. It's not perfect; please let me know if you have suggestions for improvement! Huge parts are just copied from the slick.codegen.AbstractSourceCodeGenerator and related classes and then slightly changed. There are also some things that are not directly related to this question, such as the addition of the java.time.* data types and the filtering of specific tables. I left them in, because they might be of use. Also note that this example is for a Postgres database.
import slick.codegen.SourceCodeGenerator
import slick.driver.{JdbcProfile, PostgresDriver}
import slick.jdbc.meta.MTable
import slick.model.Column
import scala.concurrent.Await
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration.Duration
object MySlickCodeGenerator {
val slickDriver = "slick.driver.PostgresDriver"
val jdbcDriver = "org.postgresql.Driver"
val url = "jdbc:postgresql://localhost:5432/dbname"
val outputFolder = "/path/to/project/src/test/scala"
val pkg = "my.package"
val user = "user"
val password = "password"
val driver: JdbcProfile = Class.forName(slickDriver + "$").getField("MODULE$").get(null).asInstanceOf[JdbcProfile]
val dbFactory = driver.api.Database
val db = dbFactory.forURL(url, driver = jdbcDriver, user = user, password = password, keepAliveConnection = true)
// The schema is generated using Liquibase, which creates these tables that I don't want to use
def excludedTables = Array("databasechangelog", "databasechangeloglock")
def tableFilter(table: MTable): Boolean = {
!excludedTables.contains(table.name.name) && schemaFilter(table.name.schema)
}
// There's also an 'audit' schema in the database, I don't want to use that one
def schemaFilter(schema: Option[String]): Boolean = {
schema match {
case Some("public") => true
case None => true
case _ => false
}
}
// Fetch data model
val modelAction = PostgresDriver.defaultTables
.map(_.filter(tableFilter))
.flatMap(PostgresDriver.createModelBuilder(_, ignoreInvalidDefaults = false).buildModel)
val modelFuture = db.run(modelAction)
// customize code generator
val codegenFuture = modelFuture.map(model => new SourceCodeGenerator(model) {
// add custom import for added data types
override def code = "import my.package.Java8DateTypes._" + "\n" + super.code
override def Table = new Table(_) {
table =>
// Use different factory and extractor functions for tables with > 22 columns
override def factory = if(columns.size == 1) TableClass.elementType else if(columns.size <= 22) s"${TableClass.elementType}.tupled" else s"${EntityType.name}.apply"
override def extractor = if(columns.size <= 22) s"${TableClass.elementType}.unapply" else s"${EntityType.name}.unapply"
override def EntityType = new EntityTypeDef {
override def code = {
val args = columns.map(c =>
c.default.map( v =>
s"${c.name}: ${c.exposedType} = $v"
).getOrElse(
s"${c.name}: ${c.exposedType}"
)
)
val callArgs = columns.map(c => s"${c.name}")
val types = columns.map(c => c.exposedType)
if(classEnabled){
val prns = (parents.take(1).map(" extends "+_) ++ parents.drop(1).map(" with "+_)).mkString("")
s"""case class $name(${args.mkString(", ")})$prns"""
} else {
s"""
/** Constructor for $name providing default values if available in the database schema. */
case class $name(${args.map(arg => {s"val $arg"}).mkString(", ")})
type ${name}List = ${compoundType(types)}
object $name {
def apply(hList: ${name}List): $name = new $name(${callArgs.zipWithIndex.map(pair => s"hList${tails(pair._2)}.head").mkString(", ")})
def unapply(row: $name) = Some(${compoundValue(callArgs.map(a => s"row.$a"))})
}
""".trim
}
}
}
override def PlainSqlMapper = new PlainSqlMapperDef {
override def code = {
val positional = compoundValue(columnsPositional.map(c => if (c.fakeNullable || c.model.nullable) s"<<?[${c.rawType}]" else s"<<[${c.rawType}]"))
val dependencies = columns.map(_.exposedType).distinct.zipWithIndex.map{ case (t,i) => s"""e$i: GR[$t]"""}.mkString(", ")
val rearranged = compoundValue(desiredColumnOrder.map(i => if(columns.size > 22) s"r($i)" else tuple(i)))
def result(args: String) = s"$factory($args)"
val body =
if(autoIncLastAsOption && columns.size > 1){
s"""
val r = $positional
import r._
${result(rearranged)} // putting AutoInc last
""".trim
} else {
result(positional)
}
s"""
implicit def $name(implicit $dependencies): GR[${TableClass.elementType}] = GR{
prs => import prs._
${indent(body)}
}
""".trim
}
}
override def TableClass = new TableClassDef {
override def star = {
val struct = compoundValue(columns.map(c=>if(c.fakeNullable)s"Rep.Some(${c.name})" else s"${c.name}"))
val rhs = s"$struct <> ($factory, $extractor)"
s"def * = $rhs"
}
}
def tails(n: Int) = {
List.fill(n)(".tail").mkString("")
}
// override column generator to add additional types
override def Column = new Column(_) {
override def rawType = {
typeMapper(model).getOrElse(super.rawType)
}
}
}
})
def typeMapper(column: Column): Option[String] = {
column.tpe match {
case "java.sql.Date" => Some("java.time.LocalDate")
case "java.sql.Timestamp" => Some("java.time.LocalDateTime")
case _ => None
}
}
def doCodeGen() = {
def generator = Await.result(codegenFuture, Duration.Inf)
generator.writeToFile(slickDriver, outputFolder, pkg, "Tables", "Tables.scala")
}
def main(args: Array[String]) {
doCodeGen()
db.close()
}
}
Update 2019-02-15: *with the release of Slick 3.3.0, as answered by #Marcus there's built-in support for code generation of tables with > 22 columns.
As of Slick 3.2.0, the simplest solution for >22 param case class is to define the default projection in the * method using mapTo instead of the <> operator (per documented unit test):
case class BigCase(id: Int,
p1i1: Int, p1i2: Int, p1i3: Int, p1i4: Int, p1i5: Int, p1i6: Int,
p2i1: Int, p2i2: Int, p2i3: Int, p2i4: Int, p2i5: Int, p2i6: Int,
p3i1: Int, p3i2: Int, p3i3: Int, p3i4: Int, p3i5: Int, p3i6: Int,
p4i1: Int, p4i2: Int, p4i3: Int, p4i4: Int, p4i5: Int, p4i6: Int)
class bigCaseTable(tag: Tag) extends Table[BigCase](tag, "t_wide") {
def id = column[Int]("id", O.PrimaryKey)
def p1i1 = column[Int]("p1i1")
def p1i2 = column[Int]("p1i2")
def p1i3 = column[Int]("p1i3")
def p1i4 = column[Int]("p1i4")
def p1i5 = column[Int]("p1i5")
def p1i6 = column[Int]("p1i6")
def p2i1 = column[Int]("p2i1")
def p2i2 = column[Int]("p2i2")
def p2i3 = column[Int]("p2i3")
def p2i4 = column[Int]("p2i4")
def p2i5 = column[Int]("p2i5")
def p2i6 = column[Int]("p2i6")
def p3i1 = column[Int]("p3i1")
def p3i2 = column[Int]("p3i2")
def p3i3 = column[Int]("p3i3")
def p3i4 = column[Int]("p3i4")
def p3i5 = column[Int]("p3i5")
def p3i6 = column[Int]("p3i6")
def p4i1 = column[Int]("p4i1")
def p4i2 = column[Int]("p4i2")
def p4i3 = column[Int]("p4i3")
def p4i4 = column[Int]("p4i4")
def p4i5 = column[Int]("p4i5")
def p4i6 = column[Int]("p4i6")
// HList-based wide case class mapping
def m3 = (
id ::
p1i1 :: p1i2 :: p1i3 :: p1i4 :: p1i5 :: p1i6 ::
p2i1 :: p2i2 :: p2i3 :: p2i4 :: p2i5 :: p2i6 ::
p3i1 :: p3i2 :: p3i3 :: p3i4 :: p3i5 :: p3i6 ::
p4i1 :: p4i2 :: p4i3 :: p4i4 :: p4i5 :: p4i6 :: HNil
).mapTo[BigCase]
def * = m3
}
EDIT
So, if you then want the slick-codegen to produce huge tables using the mapTo method described above, you override the relevant parts to the code generator and add in a mapTo statement:
package your.package
import slick.codegen.SourceCodeGenerator
import slick.{model => m}
class HugeTableCodegen(model: m.Model) extends SourceCodeGenerator(model) with GeneratorHelpers[String, String, String]{
override def Table = new Table(_) {
table =>
// always defines types using case classes
override def EntityType = new EntityTypeDef{
override def classEnabled = true
}
// allow compound statements using HNil, but not for when "def *()" is being defined, instead use mapTo statement
override def compoundValue(values: Seq[String]): String = {
// values.size>22 assumes that this must be for the "*" operator and NOT a primary/foreign key
if(hlistEnabled && values.size > 22) values.mkString("(", " :: ", s" :: HNil).mapTo[${StringExtensions(model.name.table).toCamelCase}Row]")
else if(hlistEnabled) values.mkString(" :: ") + " :: HNil"
else if (values.size == 1) values.head
else s"""(${values.mkString(", ")})"""
}
// should always be case classes, so no need to handle hlistEnabled here any longer
override def compoundType(types: Seq[String]): String = {
if (types.size == 1) types.head
else s"""(${types.mkString(", ")})"""
}
}
}
You then structure the codegen code in a separate project as documented so that it generates the source at compile time. You can pass your classname as an argument to the SourceCodeGenerator you're extending:
lazy val generateSlickSchema = taskKey[Seq[File]]("Generates Schema definitions for SQL tables")
generateSlickSchema := {
val managedSourceFolder = sourceManaged.value / "main" / "scala"
val packagePath = "your.sql.table.package"
(runner in Compile).value.run(
"slick.codegen.SourceCodeGenerator", (dependencyClasspath in Compile).value.files,
Array(
"env.db.connectorProfile",
"slick.db.driver",
"slick.db.url",
managedSourceFolder.getPath,
packagePath,
"slick.db.user",
"slick.db.password",
"true",
"your.package.HugeTableCodegen"
),
streams.value.log
)
Seq(managedSourceFolder / s"${packagePath.replace(".","/")}/Tables.scala")
}
There are few options available as you have already found out - nested tuples, conversion from Slick HList to Shapeless HList and then to case classes and so on.
I found all those options too complicated for the task and went with customised Slick Codegen to generate simple wrapper class with accessors.
Have a look at this gist.
class MyCodegenCustomisations(model: Model) extends slick.codegen.SourceCodeGenerator(model){
import ColumnDetection._
override def Table = new Table(_){
table =>
val columnIndexByName = columns.map(_.name).zipWithIndex.toMap
def getColumnIndex(columnName: String): Option[Int] = {
columnIndexByName.get(columnName)
}
private def getWrapperCode: Seq[String] = {
if (columns.length <= 22) {
//do not generate wrapper for tables which get case class generated by Slick
Seq.empty[String]
} else {
val lines =
columns.map{c =>
getColumnIndex(c.name) match {
case Some(colIndex) =>
//lazy val firstname: Option[String] = row.productElement(1).asInstanceOf[Option[String]]
val colType = c.exposedType
val line = s"lazy val ${c.name}: $colType = values($colIndex).asInstanceOf[$colType]"
line
case None => ""
}
}
Seq("",
"/*",
"case class Wrapper(private val row: Row) {",
"// addressing HList by index is very slow, let's convert it to vector",
"private lazy val values = row.toList.toVector",
""
) ++ lines ++ Seq("}", "*/", "")
}
}
override def code: Seq[String] = {
val originalCode = super.code
originalCode ++ this.getWrapperCode
}
}
}
This issue is solved in Slick 3.3:
https://github.com/slick/slick/pull/1889/
This solution provides def * and def ? and also supports plain SQL.
I am looking to use the Slick 3 framework for a Scala application to manage database interactions. I have been able to automatically generate the necessary table objects using Slick, but I also would like an integration test that verifies that the schemas in the database match the schemas in the objects. This is because sometimes tables get altered without my team being alerted, and so we would prefer to catch the change in an integration test instead of a production application.
One way to do this is to simply run a select query on every single table in a test runner. However, I feel like there should be a more direct way. Furthermore, it is not clear to me how to systematically run through all the tables defined in the file, except to manually append the table object to some sequence the test runner moves through. I notice that there is a schema field, but it only has the ability to generate create and drop statements.
Any help would be greatly appreciated. Thank you!
EDIT:
Here is my solution, but I was hoping for a better one:
class TablesIT extends FunSuite with BeforeAndAfter with ScalaFutures {
var db: Database = _
before{ db = Database.forURL( /* personal details */ )}
object ResultMap extends GetResult[Map[String,Any]] { //Object borrowed from http://stackoverflow.com/questions/20262036/slick-query-multiple-tables-databases-with-getting-column-names
def apply(pr: PositionedResult) = {
val rs = pr.rs // <- jdbc result set
val md = rs.getMetaData
val res = (1 to pr.numColumns).map{ i=> md.getColumnName(i) -> rs.getObject(i) }.toMap
pr.nextRow // <- use Slick's advance method to avoid endless loop
res
}
}
def testTableHasCols[A <: Table[_]](table: slick.lifted.TableQuery[A]): Unit = {
whenReady(db.run(table.take(1).result.headOption.asTry)) { case Success(t) => t match {
case Some(r) => logTrace(r.toString)
case None => logTrace("Empty table")
}
case Failure(ex) => fail("Query exception: " + ex.toString)
}
}
def plainSqlSelect[A](query: String)(implicit gr: GetResult[A]): Future[Seq[A]] = {
val stmt = sql"""#$query""".as[A]
db.run(stmt)
}
def compareNumOfCols[A <: Table[_]](table: slick.lifted.TableQuery[A]) = {
val tableName = table.baseTableRow.tableName
val selectStar = whenReady(db.run(sql"""select * from #$tableName limit 1""".as(ResultMap).headOption)) {
case Some(m) => m.size
case None => 0
}
val model = whenReady(db.run(sql"""#${table.take(1).result.statements.head}""".as(ResultMap).headOption)) {
case Some(m) => m.size
case None => 0
}
assert(selectStar === model, "The number of columns do not match")
}
test("Test table1") {
testTableHasCols(Table1)
compareNumOfCols(Table1)
}
// And on for each table
}
I ended up devising a better solution that uses the following idea. It is more or less the same, and unfortunately I still have to manually create a test for each table, but the method is cleaner, I think. Note, however, that this only works for PostgreSQL because of the information schema, but other database systems have other methods.
class TablesIT extends FunSuite with BeforeAndAfter with ScalaFutures {
var db: Database = _
before{ db = Database.forURL( /* personal details */ )}
def testTableHasCols[A <: Table[_]](table: slick.lifted.TableQuery[A]): Unit = {
whenReady(db.run(table.take(1).result.headOption.asTry)) { case Success(t) => t match {
case Some(r) => logTrace(r.toString)
case None => logTrace("Empty table")
}
case Failure(ex) => fail("Query exception: " + ex.toString)
}
}
def compareNumOfCols[A <: Table[_]](table: slick.lifted.TableQuery[A]) = {
val tableName = table.baseTableRow.tableName
val selectStar = whenReady(db.run(sql"""select column_name from information_schema.columns where table_name='#$tableName'""".as[String])) {
case m: Seq[String] => m.size
case _ => 0
}
val model = table.baseTableRow.create_*.map(_.name).toSeq.size
assert(selectStar === model, "The number of columns do not match")
}
test("Test table1") {
testTableHasCols(Table1)
compareNumOfCols(Table1)
}
// And on for each table
}
I'm trying ScalaQuery, it is really amazing. I could defined the database table using Scala class, and query it easily.
But I would like to know, in the following code, how could I check if a table is exists, so I won't call 'Table.ddl.create' twice and get a exception when I run this program twice?
object Users extends Table[(Int, String, String)]("Users") {
def id = column[Int]("id")
def first = column[String]("first")
def last = column[String]("last")
def * = id ~ first ~ last
}
object Main
{
val database = Database.forURL("jdbc:sqlite:sample.db", driver = "org.sqlite.JDBC")
def main(args: Array[String]) {
database withSession {
// How could I know table Users is alrady in the DB?
if ( ??? ) {
Users.ddl.create
}
}
}
}
ScalaQuery version 0.9.4 includes a number of helpful SQL metadata wrapper classes in the org.scalaquery.meta package, such as MTable:
http://scalaquery.org/doc/api/scalaquery-0.9.4/#org.scalaquery.meta.MTable
In the test code for ScalaQuery, we can see examples of these classes being used. In particular, see org.scalaquery.test.MetaTest.
I wrote this little function to give me a map of all the known tables, keyed by table name.
import org.scalaquery.meta.{MTable}
def makeTableMap(dbsess: Session) : Map[String, MTable] = {
val tableList = MTable.getTables.list()(dbsess);
val tableMap = tableList.map{t => (t.name.name, t)}.toMap;
tableMap;
}
So now, before I create an SQL table, I can check "if (!tableMap.contains(tableName))".
This thread is a bit old, but maybe someone will find this useful. All my DAOs include this:
def create = db withSession {
if (!MTable.getTables.list.exists(_.name.name == MyTable.tableName))
MyTable.ddl.create
}
Here's a full solution that checks on application start using a PostGreSQL DB for PlayFramework
import globals.DBGlobal
import models.UsersTable
import org.scalaquery.meta.MTable
import org.scalaquery.session.Session
import play.api.GlobalSettings
import play.api.Application
object Global extends GlobalSettings {
override def onStart(app: Application) {
DBGlobal.db.withSession { session : Session =>
import org.scalaquery.session.Database.threadLocalSession
import org.scalaquery.ql.extended.PostgresDriver.Implicit._
if (!makeTableMap(session).contains("tableName")) {
UsersTable.ddl.create(session)
}
}
}
def makeTableMap(dbsess: Session): Map[String, MTable] = {
val tableList = MTable.getTables.list()(dbsess)
val tableMap = tableList.map {
t => (t.name.name, t)
}.toMap
tableMap
}
}
With java.sql.DatabaseMetaData (Interface). Depending on your Database, more or less functions might be implemented.
See also the related discussion here.I personally prefer hezamu's suggestion and extend it as follows to keep it DRY:
def createIfNotExists(tables: TableQuery[_ <: Table[_]]*)(implicit session: Session) {
tables foreach {table => if(MTable.getTables(table.baseTableRow.tableName).list.isEmpty) table.ddl.create}
}
Then you can just create your tables with the implicit session:
db withSession {
implicit session =>
createIfNotExists(table1, table2, ..., tablen)
}
You can define in your DAO impl the following method (taken from Slick MTable.getTables always fails with Unexpected exception[JdbcSQLException: Invalid value 7 for parameter columnIndex [90008-60]]) that gives you a true o false depending if there a defined table in your db:
def checkTable() : Boolean = {
val action = MTable.getTables
val future = db.run(action)
val retVal = future map {result =>
result map {x => x}
}
val x = Await.result(retVal, Duration.Inf)
if (x.length > 0) {
true
} else {
false
}
}
Or, you can check if some "GIVENTABLENAME" or something exists with println method:
def printTable() ={
val q = db.run(MTable.getTables)
println(Await.result(q, Duration.Inf).toList(0)) //prints first MTable element
println(Await.result(q, Duration.Inf).toList(1))//prints second MTable element
println(Await.result(q, Duration.Inf).toList.toString.contains("MTable(MQName(public.GIVENTABLENAME_pkey),INDEX,null,None,None,None)"))
}
Don't forget to add
import slick.jdbc.meta._
Then call the methods from anywhere with the usual #Inject(). Using
play 2.4 and play-slick 1.0.0.
Cheers,