aehuynh / siderdb

An in-memory, key-value database

SiderDB

An in-memory, key-value database that supports transactions

How to Run

SiderDB requires Python 3.4.3. It is a command line program. To start the database command line: python src/database.py

Transactions

The database runs all commands and changes its state permanantely even when there is an open transaction. When the database runs a command, it supports transactions by creating and saving "undo" commands that undo the current command to a transaction block.

A transaction block represents a transaction. Transaction blocks are kept in a stack.

On rollback, the database pops a transaction block off the stack and runs the undo commands of that block.

On commit, the database removes all the transaction blocks from the stack.

Command Syntax

Commands and arguments are split by spaces. Commands will not run without the correct number of arguments.

Keys and values can be any valid string of non-whitespace characters.

Commands do not support quotes. The command SET tomato "fruit" sets tomato to the value "fruit" which incudes the quotes. The command SET "jones " sets "jones to the value ".

Regular Commands

• SET key value - Set the variable key to value. Overwrites key if it already exists.
• GET key - Print the value of the variable key. Prints NULL if key is not in the database.
• NUMEQUALTO value - Print the number of variables that are set to the specified value.
• UNSET key - Delete the variable key if it exists.
• END - End the program.

Transaction Commands

• BEGIN - Create a new transaction. Transactions can be nested.
• ROLLBACK - Undo the changes of the most recently created transaction and close the transaction. Prints NO TRANSACTION if there are no open transactions.
• COMMIT - Commits all open transactions and closes them. Prints NO TRANSACTION if there are no open transactions.