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Clojure data processing framework with parallel computing on larger-than-memory datasets


  • Unlimited Size

    It supports datasets larger than memory.

  • Various Operations

    Although Clojask is designed for larger-than-memory datasets, like NoSQLs, it does not sacrifice common operations on relational dataframes, such as group by, aggregate, join.

  • Fast

    Faster than Dask in most operations, and the larger the dataframe is, the bigger the advantage. Please find the benchmarks here.

  • All Native Types

    All the datatypes used to store data are native Clojure (or Java) types.

  • From File to File

    Integrate IO inside the dataframe. No need to write your own read-in and output functions.

  • Parallel

    Most operations could be executed into multiple threads or even machines. See the principle in Onyx.

  • Lazy Operations

    Most operations will not be executed immediately. Dataframe will intelligently pipeline the operations altogether in computation.

  • Little Constraints on programming

    Except for some aggregations where you need to write customized functions subject to simple templates, operations in Clojask support arbitrary Clojure functions as input


Available on Clojars Clojars Project.

Insert this line into your project.clj if using Leiningen.

[com.github.clojure-finance/clojask "2.0.2"]

Insert this line into your deps.edn if using CLI.

com.github.clojure-finance/clojask {:mvn/version "2.0.2"}


  • MacOS or Linux
  • Java 8 - 11

Example Usage

  1. Import Clojask

    (require '[clojask.dataframe :as ck])
  2. Initialize a dataframe

    (def df (ck/dataframe "Employees-example.csv"))

    The source file can be found here.

    See dataframe

  3. Preview the first few lines of the dataframe

    (ck/print-df df)


    See print-df

  4. Change the data type of some columns

    (ck/set-type df "Salary" "double")
    (ck/set-type df "UpdateDate" "date:yyyy/MM/dd")
    (ck/print-df df)


    See set-type

  5. Add 100 to Bob as NewSalary

    (ck/operate df (fn [EmployeeName Salary] (if (= EmployeeName "Bob") (+ Salary 100) Salary)) ["EmployeeName" "Salary"] "NewSalary")
    (ck/print-df df)


    See operate

  6. Output the resultant dataset to "result.csv" (Use 8 threads)

    (ck/compute df 8 "result.csv" :select ["Employee" "EmployeeName" "Department" "NewSalary" "UpdateDate"])

    See compute

Supported Functions and Procedures

clojask functions

  • The solid arrows point to the fixed next step; dotted arrows point to all possible next steps.
  • Any step except for Initialization is optional.


The detailed documentation for every API can be found here.


A separate repository for some typical usage of Clojask can be found here.

Problem Feedback

If your question is not answered in existing issues, feel free to create a new one.

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