The Haskell in-memory interactive database - HimiDB

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• Realised at MuniHac 2018

Idea

Joshua Backfield’s book, Becoming Functional: Steps for Transforming Into a Functional Programmer, introduces a very simple database engine written in Scala. This project is to convert this system into Haskell, and build a CLI frontend for it in a purer way than the Scala system uses.

Building and executing:

stack build
stack test
stack exec himiDB

Built With

• Haskellstack - The Haskell Tool Stack
• Hspec - A Testing Framework For Haskell
• Megaparsec - A Haskell parsing library, used for the CLI
• Haskeline - A Haskell command line interface

Demo

HimiDB v0.1
The Haskell In-Memory Interactive Database System
Created for the MuniHac 2018
type `help` for instructions

himiDB > create users (id int, name string) a table to describe my subscribers
himiDB > insert users (1, "me") (2, "you") (3, "him")
himiDB > insert users ("them", 4)
Error: Wrong type for column id
himiDB > describe
users (id int, name string) a table to describe my subscribers
himiDB > describe users
users: a table to describe my subscribers
id  | name
int | string
----+-------
3   | "him"
2   | "you"
1   | "me"
himiDB > select users * where name == "me" || id > 2
3 | "him"
1 | "me"

himiDB CLI

Usage:

- create:
    Create a table
    > create myTable (a int, b int, c int)
    > create tableName (col1 int, col2 string) description goes here

- drop:
    Delete a table and its contents
    > drop tableName

- describe:
    Show all tables, or the data of one table
    > describe
    > describe tableName

- insert:
    Insert a row into a table
    > insert tableName (1, "me")
    > insert tableName (1, "me") (2, "you")

- select:
    Select data from a table
    > select tableName *
    > select tableName col1
    > select tableName (col1, col2)
    > select tableName * where col1 > 4 || col2 == "me"

- delete:
    Delete data from a table
    > delete tableName
    > delete tableName where col1 > 4 || col2 == "me"

- help:
    Show the help guide, with examples

- exit:
    Exit and clear the database
    > ^D