gosql

An early PostgreSQL implementation in Go.

Example

$ git clone [email protected]:eatonphil/gosql
$ cd gosql
$ go run cmd/main.go
Welcome to gosql.
# CREATE TABLE users (name TEXT, age INT);
ok
#  INSERT INTO users VALUES ('Stephen', 16);
ok
# SELECT name, age FROM users;
   name   | age
----------+------
  Stephen |  16
(1 result)
ok
# INSERT INTO users VALUES ('Adrienne', 23);
ok
# SELECT age + 2, name FROM users WHERE age = 23;
  age |   name
------+-----------
   25 | Adrienne
(1 result)
ok
# SELECT name FROM users;
    name
------------
  Stephen
  Adrienne
(2 results)
ok

Architecture

• cmd/main.go
  • Contains the REPL and high-level interface to the project
  • Dataflow is: user input -> lexer -> parser -> in-memory backend
• lexer.go
  • Handles breaking user input into tokens for the parser
• parser.go
  • Matches a list of tokens into an AST or fails if the user input is not a valid program
• memory.go
  • An example, in-memory backend supporting the Backend interface (defined in backend.go)

Contributing

• Add a new operator (such as <, >, etc.) supported by PostgreSQL
• Add a new data type supported by PostgreSQL

In each case, you'll probably have to add support in the lexer, parser, and in-memory backend. I recommend going in that order.

In all cases, make sure the code is formatted (make fmt) and passes tests (make test). New code should have tests.

Blog series

• [https://notes.eatonphil.com/database-basics.html](Writing a SQL database from scratch in Go)

Further reading

Here are some similar projects written in Go.

• go-mysql-server
  • This is a MySQL frontend (with an in-memory backend for testing only).
• ramsql
  • This is a WIP PostgreSQL-compatible in-memory database.
• CockroachDB
  • This is a production-ready PostgreSQL-compatible database.