# MiniSQL

## Project Structure
- `client` - REPL client for connecting to the server
- `server` - MiniSQL server
- `minisql` - SQL AST interpreter
- `parser` - SQL parser
- `proto` - Implementation of subset of PostgreSQL protocol

## Requirements
- Rust + Cargo with version **>= 1.74.0** (using `impl` in return statements)
- Optional: `psql` cli for testing the server

# Usage

## Running the server
```bash
cargo run -p server -- [OPTIONS] --file <FILE>
```
```
Options:
  -a, --address <ADDRESS>  IP address for the server to listen on [default: 127.0.0.1]
  -p, --port <PORT>        Port for the server to listen on [default: 5432]
  -f, --file <FILE>        Path to the data file
  -h, --help               Print help
```

This will start the server listening on `<ADDRESS>:<PORT>` and load the state from `<FILE>`.
If the `<FILE>` does not exist, it will be created.

### Demo Database
A database with demo data is available in `demo.json`. To run the server with this database, use:
```bash
cargo run -p server -- --file demo.json
```

This database contains two tables:
- Table `users` with columns `id`, `name`, `surname`, `email`
- Table `cars` with columns `id`, `vid`, `brand`, `model`, `year`

## Running the client
```bash
cargo run -p client -- [OPTIONS]
```
```
Options:
  -p, --port <PORT>          Port number of the server [default: 5432]
      --host <HOST>          Host name or IP address of the server [default: 127.0.0.1]
      --username <USERNAME>  User name [default: "minisql user"]
  -h, --help                 Print help
```

This will start a REPL client that connects to the server at `<HOST>:<PORT>` and authorizes with `<USERNAME>`.
SQL queries can be entered line by line. The client will print the result of each query.

To exit the REPL client, enter `exit` or `quit`.

# Features
- SQL must be on single line, in **UPPERCASE** and end with `;`, as it should be
- Supported operations: `CREATE TABLE`, `CREATE INDEX`, `SELECT`, `INSERT`, `DELETE`
- Supported data types: `UUID`, `STRING`, `INT`, `NUMBER`
- Supported subset of PostgreSQL protocol, without authentication and simple query flow

## Operations

### `CREATE TABLE`
- Every table requires one column with type `UUID` as `PRIMARY KEY`

```sql
CREATE TABLE <TableName> (<ColumnName> <DataType>, ...);
```

With the demo database, this can be used to create a new table:
```sql
CREATE TABLE games (id UUID PRIMARY KEY, name STRING, year INT, price NUMBER);
```

### `CREATE INDEX`
- Indexing is not supported for the `NUMBER` data type

```sql
CREATE INDEX <IndexName> ON <TableName> (<ColumnName>);
```

With the demo database, this can be used to create a new index:
```sql
CREATE INDEX CarsYear ON cars (year);
```

### `SELECT`
- `WHERE` clause is optional and only equality is supported
- All columns can be selected with `*`

```sql
SELECT <ColumnName>, ... FROM <TableName> [WHERE <ColumnName> = <Value>];
```

With the demo database, this can be used to select all cars with year 2001:
```sql
SELECT * FROM cars WHERE year = 2001;
```

### `INSERT`

```sql
INSERT INTO <TableName> (<ColumnName>, ...) VALUES (<Value>, ...);
```

With the demo database, this can be used to insert a new user:
```sql
INSERT INTO users (id, name, surname, email) VALUES (u12345, "John", "Doe", "johhny.trucker@seznam.cz");
```


### `DELETE`
- `WHERE` clause is optional and only equality is supported

```sql
DELETE FROM <TableName> [WHERE <ColumnName> = <Value>];
```

With the demo database, this can be used to delete all users with name Christina:
```sql
DELETE FROM users WHERE name = "Christina";
```

## Data Types
- `UUID` - special integer prefixed with `u`, e.g. `u12345`
- `STRING` - string enclosed in double quotes, e.g. `"Hello World"`
- `INT` - integer, e.g. `12345`
- `NUMBER` - floating point number, e.g. `123.45`

## Testing with `psql`
Thanks to the subset of PostgreSQL protocol implemented in `proto`, the server can be tested with `psql`,
which offers REPL client similar to the `client` crate:
```bash
psql -h <HOST> -p <PORT>
```