Recent questions tagged Scala

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scala - How to designate a thread pool for actors

I have an existing java/scala application using a global thread pool. I would like to start using actors in ... already using threads? Thanks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to execute multi line sql in spark sql

How can I execute lengthy, multiline Hive Queries in Spark SQL? Like query below: val sqlContext = new HiveContext (sc) val ... ... from ... "); See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark : How to union all dataframe in loop

Is there a way to get the dataframe that union dataframe in loop? This is a sample code: var fruits = ... ,orange aaa,bbb,melon Thanks again See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - SBT Test Error: java.lang.NoSuchMethodError: net.jpountz.lz4.LZ4BlockInputStream

Getting Below exception , when i tried to perform unit tests for my spark streaming code on SBT windows using ... .0.5 Any suggestions ? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Play Framework: Dependency Inject Action Builder

since Play Framework 2.4 there is the possibility to use dependency injection (with Guice). Before ... in my ActionBuilder? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - rely on methods of case class in trait

Is there a way to rely on methods defined in case class in a trait? E.g., copy: the following doesn't work. I' ... val y: String) extends K[L] ^ See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Adding a column of rowsums across a list of columns in Spark Dataframe

I have a Spark dataframe with several columns. I want to add a column on to the dataframe that is a sum of ... Thanks in advance for your help. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - multiple joins with slick

For joining between two tables is done like (for { (computer, company) <- Computers leftJoin Companies on (_ ... like filter.toLowerCase() } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to add columns into org.apache.spark.sql.Row inside of mapPartitions

I am a newbie at scala and spark, please keep that in mind :) Actually, I have three questions How should ... created RDD Thank you at advance See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Reading multiple files from S3 in Spark by date period

Description I have an application, which sends data to AWS Kinesis Firehose and this writes the data into my ... between some date interval? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Spark-SQL : How to read a TSV or CSV file into dataframe and apply a custom schema?

I'm using Spark 2.0 while working with tab-separated value (TSV) and comma-separated value (CSV) files. I want ... and apply a schema to them? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to use TailCalls?

If I understand correctly, scala.util.control.TailCalls can be used to avoid stack overflows for non-tail-recursive ... this kind of problem? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Conditional Join in Spark DataFrame

I am trying to join two DataFrame with condition. I have two dataframe A and B. A contains id,m_cd and ... if there any other option available. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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833 views

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scala - How can I get the current SparkSession in any place of the codes?

I have created a session in the main() function, like this: val sparkSession = SparkSession.builder.master("local[* ... scala. What should I do? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - What is the difference between ArrayBuffer and Array

I'm new to scala/java and I have troubles getting the difference between those two. By reading the ... performance variation between those two? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Akka 2.1 minimal remote actor example

EDIT Notice, I needed to make the reverse changes of this https://github.com/akka/akka/commit/ ... a simple working application. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Create array of literals and columns from List of Strings in Spark SQL

I am trying to define functions in Scala that take a list of strings as input, and converts them into ... and for any suggestions/solutions. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Passing a Shapeless Extensible Record to a Function

I am trying to learn Shapeless (using version 2.10.2). I have created a very simple extensible record: val ... to express that type in code! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Convert normal recursion to tail recursion

I was wondering if there is some general method to convert a "normal" recursion with foo(...) + foo( ... : Stackless Scala With Free Monads See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Date conversion

I have a date variable var date: Date = new Date() then I have converted this date to String: var dateStr = ... cannot be cast to java.util.Date See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Problems with SBT dependencies in Intellij Idea

This is a problem that is really getting on my nerves. I'm writing proofs for the ... inox.git#53ea4533a957050bd6a968d5a340890bd54998a5")) } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - MatchError when match receives an IndexedSeq but not a LinearSeq

Is there a reason that match written against Seq would work differently on IndexedSeq types than the way it does on ... MatchError(temp6) } }; See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - Anorm LIKE clause with String Interpolation

Is it possible to use LIKE clause with String Interpolation in Anorm? // e.g. this doesn't work SQL" ... users WHERE last_name LIKE 'Smi%'; See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala self-type: value is not a member error

This is a followup to this question. I'm trying to implement vectors in scala with a generic super class ... from my lack of understanding. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - How to convert a column from hex string to long?

I have a DataFrame with Icao column with hex codes that I would like to convert to Long datatype. How could I ... |471F5F|72133| |40612C|69676| See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.5k views

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scala - Process all columns / the entire row in a Spark UDF

For a dataframe containing a mix of string and numeric datatypes, the goal is to create a new features column ... ) as features from mytable") See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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855 views

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scala - How to flatten list of options using higher order functions?

Using Scala 2.7.7: If I have a list of Options, I can flatten them using a for-comprehension: val ... . That seems clunky. Any advice? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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scala - What is a diverging implicit expansion error?

While trying to find a solution to another question ([1]) I came across a diverging implicit expansion error. I'm ... Seq[T]) = s.sorted ^ See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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