How do you list collections in a database using ReactiveMongo?
This is how:
def listImportCollections = {
val result = db.collectionNames
result onComplete {
case Success(r) =>
println("result: " + r)
case Failure(t) =>
println("fail: " + t)
}
}
API doc for this here.
Related
I am an absolute beginner in Scala, but have this problem to solve.
So i have a list of parameters
itemList = List('abc', 'def', 'ghi','jkl','mno', 'pqr')
I have these 3 parameter queries
val q1 = "env='dev1'&id='123'&listitem='xyz'"
val q2 = "env='dev2'&id='1234'&listitem='xyz'"
val q3 = "env='dev3'&id='12345'&listitem='xyz'"
val report1 = getReport(q1)
val report2 = getReport(q2)
val report3 = getReport(q3)
So I am trying to loop through the list, replace the listitem parameter in q1, q2 and q3 with the listitem and then run the http request report for each item in the list.
Since each getReport request is asynchronous, i need to wait , and so i cannot go to the next item in the list, as it would be if i were to do a loop.
So i would like to start up 3 threads for each item in the list and then combine the 3 reports into 1 final one, or i could do it sequentially.
How would i go about doing it with 3 Threads for each item in the list?
This is my idea:
val reportToken = [ q1, q2,q3 ]
val listTasks = [ getReport(q1) , getReport(q2) , getReport(q3) ]
for (i <- 1 to 3) {
val thread = new Thread {
override def run {
listTasks (reportToken(i))
}
val concat += listTask(i)
}
thread.start
Thread.sleep(50)
}
You can wrap each of your tasks in a Future, apply map/recover to handle the successful/failed Futures, and use Future.sequence to transform the list of Futures into a Future of list. Here's a trivialized example:
import scala.concurrent.{Future, Await}
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration.Duration
def getReport(q: String) = q match {
case "q2" => throw new Exception()
case q => s"got $q"
}
val reportToken = Seq("q1", "q2", "q3")
val listTasks = reportToken.map( q => Future{ getReport(q) } )
// listTasks: Seq[scala.concurrent.Future[String]] = ...
val f = Future.sequence(
listTasks.map(_.map(Some(_)).recover{case _ => None})
)
// f: scala.concurrent.Future[Seq[Option[String]]] = ...
Await.result(f, Duration.Inf)
// res1: Seq[Option[String]] = List(Some(got q1), None, Some(got q3))
For more details about Futures, here's a relevant Scala doc.
Assuming def getReport(str: String): Future[HttpResponse]
Future.sequence(itemList.map( item => {
for {
report1 <- getReport(q1.replace("xyz", item))
report2 <- getReport(q2.replace("xyz", item))
report3 <- getReport(q3.replace("xyz", item))
} yield {
(report1, report2, report3)
}
})).onComplete {
case Success(res) => // do something
case Failure(err) => // handle error
}
Having list of documents as below mentioned.
Document1:
{
id:1,
PostList:[
{
postname:"aaa",
lastdatetime:2017-07-13T17:10:25+05:30,
sname:"sas"
},
{
postname:"aaa1",
lastdatetime:2017-07-14T17:10:25+05:30,
sname:"sasadd"
},
{
postname:"aaa2",
lastdatetime:2017-07-10T17:10:25+05:30,
sname:"weq"
}
]
}
Document2:
{
id:2,
PostList:[
{
postname:"aaa",
lastdatetime:2017-07-13T17:10:25+05:30,
sname:"sas"
},
{
postname:"aaa1",
lastdatetime:2017-07-14T17:10:25+05:30,
sname:"sasadd"
},
{
postname:"aaa2",
lastdatetime:2017-07-10T17:10:25+05:30,
sname:"weq"
}
]
}
I need a list of postnames which is equal to "aaa" with orderby lastdatetime.
I am able to get query
select f.lastdatetime,f.postname
from c
join f in c.PostList
where f.postname='aaa'
But I need to get the list with orderby lastdatetime.
When I try the below query, I am getting an error
Order-by over correlated collections is not supported
select f.lastdatetime,f.postname
from c
join f in c.PostList
where f.postname='aaa' ORDER BY f.lastdatetime ASC
Does anybody have an idea to get through?
As #Rafat Sarosh said in the comment :Order-by over correlated collections is not supported and it will be enable in the future.
However, I suggest a workaround for you to track for your solution: use Azure Cosmos DB UDF.
You could pass the results of your query as parameters to the UDF for sorting processing.
Query Sql:
select f.lastdatetime,f.postname
from c
join f in c.PostList
where f.postname='aaa'
UDF sample code:
function userDefinedFunction(arr){
var i = arr.length, j;
var tempExchangVal;
while (i > 0) {
for (j = 0; j < i - 1; j++) {
if (arr[j].lastdatetime < arr[j + 1].lastdatetime) {
tempExchangVal = arr[j];
arr[j] = arr[j + 1];
arr[j + 1] = tempExchangVal;
}
}
i--;
}
return arr;
}
Hope it helps you.
I'm trying to catch an SQL error in Slick 3.x. The code below doesn't print anything, but if traced under debug, it works fine (it prints the failure). What's wrong with this code?
object TestSlick extends App {
val db = Database.forConfig("dbconfig")
val sql = "update table_does_not_exist set zzz=1 where ccc=2"
val q = sqlu"#$sql"
db.run(q.asTry).map {result =>
result match {
case Success(r) => println(r)
case Failure(e) => {
println(s"SQL Error, ${e.getMessage}")
println("command:" + sql)
throw e
}
}
}
}
This works, a future is needed, thanks to lxx for the tip
val future = db.run(q.asTry).map {result =>
result match {
case Success(r) => println(r)
case Failure(e) => {
println(s"SQL Error, ${e.getMessage}")
println("command:" + sql)
throw e
}
}
}
Await.result(future, Duration.Inf)
First of I would like to state that I am new to slick and am using version 3.1.1 . I been reading the manual but i am having trouble getting my query to work. Either something is wrong with my connection string or something is wrong with my Slick code. I got my config from here http://slick.typesafe.com/doc/3.1.1/database.html and my update example from here bottom of page http://slick.typesafe.com/doc/3.1.1/queries.html . Ok so here is my code
Application Config.
mydb= {
dataSourceClass = org.postgresql.ds.PGSimpleDataSource
properties = {
databaseName = "Jsmith"
user = "postgres"
password = "unique"
}
numThreads = 10
}
My Controller -- Database table is called - relations
package controllers
import play.api.mvc._
import slick.driver.PostgresDriver.api._
class Application extends Controller {
class relations(tag: Tag) extends Table[(Int,Int,Int)](tag, "relations") {
def id = column[Int]("id", O.PrimaryKey)
def me = column[Int]("me")
def following = column[Int]("following")
def * = (id,me,following)
}
val profiles = TableQuery[relations]
val db = Database.forConfig("mydb")
try {
// ...
} finally db.close()
def index = Action {
val q = for { p <- profiles if p.id === 2 } yield p.following
val updateAction = q.update(322)
val invoker = q.updateStatement
Ok()
}
}
What could be wrong with my code above ? I have a separate project that uses plain JDBC and this configuration works perfectly for it
db.default.driver=org.postgresql.Driver
db.default.url="jdbc:postgresql://localhost:5432/Jsmith"
db.default.user="postgres"
db.default.password="unique"
You did not run your action yet. db.run(updateAction) executes your query respectively your action on a database (untested):
def index = Action.async {
val q = for { p <- profiles if p.id === 2 } yield p.following
val updateAction = q.update(322)
val db = Database.forConfig("mydb")
db.run(updateAction).map(_ => Ok())
}
db.run() returns a Future which will be eventually completed. It is then simply mapped to a Result in play.
q.updateStatement on the other hand just generates a sql statement. This can be useful while debugging.
Look the code from my project:
def updateStatus(username: String, password: String, status: Boolean): Future[Boolean] = {
db.run(
(for {
user <- Users if user.username === username
} yield {
user
}).map(_.online).update(status)
}
I have a pretty normal join that I create via JoinSqlBuilder
var joinSqlBuilder = new JoinSqlBuilder<ProductWithManufacturer, Product>()
.Join<Product, Manufacturer>(sourceColumn: p => p.ManufacturerId,
destinationColumn: mf => mf.Id,
sourceTableColumnSelection: p => new { ProductId = p.Id, ProductName = p.Name },
destinationTableColumnSelection: m => new { ManufacturerId = m.Id, ManufacturerName = m.Name })
Of course, the join created by this could potentially return a lot of rows, so I want to use paging - preferably on the server-side. However, I cannot find anything in the JoinSqlBuilder which would let me do this? Am I missing something or does JoinSqlBuilder not have support for this (yet)?
If you aren't using MS SQL Server I think the following will work.
var sql = joinSqlBuilder.ToSql();
var data = this.Select<ProductWithManufacturer>(
q => q.Select(sql)
.Limit(skip,rows)
);
If you are working with MS SQL Server, it will most likely blow up on you. I am working to merge a more elegant solution similar to this into JoinSqlBuilder. The following is a quick and dirty method to accomplish what you want.
I created the following extension class:
public static class Extension
{
private static string ToSqlWithPaging<TResult, TTarget>(
this JoinSqlBuilder<TResult, TTarget> bldr,
string orderColumnName,
int limit,
int skip)
{
var sql = bldr.ToSql();
return string.Format(#"
SELECT * FROM (
SELECT ROW_NUMBER() OVER (ORDER BY [{0}]) As RowNum, *
FROM (
{1}
)as InnerResult
)as RowConstrainedResult
WHERE RowNum > {2} AND RowNum <= {3}
", orderColumnName, sql, skip, skip + limit);
}
public static string ToSqlWithPaging<TResult, TTarget>(
this JoinSqlBuilder<TResult, TTarget> bldr,
Expression<Func<TResult, object>> orderSelector,
int limit,
int skip)
{
var member = orderSelector.Body as MemberExpression;
if (member == null)
throw new ArgumentException(
"TResult selector refers to a non member."
);
var propInfo = member.Member as PropertyInfo;
if (propInfo == null)
throw new ArgumentException(
"TResult selector refers to a field, it must be a property."
);
var orderSelectorName = propInfo.Name;
return ToSqlWithPaging(bldr, orderSelectorName, limit, skip);
}
}
It is applied as follows:
List<Entity> GetAllEntities(int limit, int skip)
{
var bldr = GetJoinSqlBuilderFor<Entity>();
var sql = bldr.ToSqlWithPaging(
entity => entity.Id,
limit,
skip);
return this.Db.Select<Entity>(sql);
}