sql-engine

A technology proof-of-concept of using MySQL and SQL to query a levelup/leveldb database.

Implemented as part of a hack project for campjs 2013.

Pull requests encouraged!

This will eventually become a plugin for the level-queryengine pluggable query engine system.

Quick start

To play around with this, git clone and npm install and start the example server and specify a port to listen to:

$ node server.js 3307

The example Server adds the following non-relational JSON documents to the local leveldb:

[
  { "name": "Bob", "num": 42, "awesome": "goodbye", "x": 99 },

  { "name": "Jane", "num": 43, "awesome": "blah",
    "car": { "make": "Toyota", "model": "Camry" } },

  { "name": "Peter", "num": 88, "awesome": "true",
    "car": { "make": "Toyota", "model": "Corolla" } }
]

Connect to the levelup MySQL server (authentication and database selection not currently implemented)

$ mysql -P 3308 --protocol=tcp

Execute some queries against the test 'users' table:

mysql> select * from users;
+-------+------+---------+------+----------+-----------+
| name  | num  | awesome | x    | car.make | car.model |
+-------+------+---------+------+----------+-----------+
| Bob   |   42 | goodbye |   99 | NULL     | NULL      |
| Jane  |   43 | blah    | NULL | Toyota   | Camry     |
| Peter |   88 | true    | NULL | Toyota   | Corolla   |
+-------+------+---------+------+----------+-----------+
3 rows in set (0.00 sec)

mysql> select name, num from users where car.make = 'Toyota';
+-------+------+
| name  | num  |
+-------+------+
|  Jane |   43 |
| Peter |   88 |
+-------+------+
2 rows in set (0.00 sec)

How it works

• sql-engine uses the awesome mysql2 library to do the MySQL proxying to look like a MySQL server protocol speaking server.
• sql-engine parses the SQL using simpleSqlParser into an AST.
• the SQL AST is then parsed into the mongodb query language and ran using jsonquery-engine against the levelup/leveldb instance.

Notes

This is highly experimental, and needs a lot more work to support the full suite of SQL operations.

• Currently only AND and OR are implemented for SQL queries.
• Currently only equality is implemented for SQL where clauses (eg. colA = colB)
• the 'FROM' statemenet will query a levelup "sublevel" by that name.
• No database authentication is implemented.
• No joins are currently implemented. I plan to use foreign-key and/or level-join to implement this.
• No sorting is implemented. I plan to use sort-stream to do that.
• simpleSqlParser also parses INSERT, DELETE and UPDATE statements, but these haven't been implemented.