## Features
### PG Wire: 

run `cargo run --features="net"` to start service

### ORM Mapping: `features = ["macros"]`
```rust
#[derive(Default, Debug, PartialEq)]
struct MyStruct {
  c1: i32,
  c2: String,
}

implement_from_tuple!(
    MyStruct, (
        c1: i32 => |inner: &mut MyStruct, value| {
            if let DataValue::Int32(val) = value {
                inner.c1 = val;
            }
        },
        c2: String => |inner: &mut MyStruct, value| {
            if let DataValue::Utf8 { value, .. } = value {
                inner.c2 = value;
            }
        }
    )
);
```

### User-Defined Function: `features = ["macros"]`
```rust
scala_function!(TestFunction::test(LogicalType::Integer, LogicalType::Integer) -> LogicalType::Integer => |v1: DataValue, v2: DataValue| {
    let plus_binary_evaluator = EvaluatorFactory::binary_create(LogicalType::Integer, BinaryOperator::Plus)?;
    let value = plus_binary_evaluator.binary_eval(&v1, &v2);

    let plus_unary_evaluator = EvaluatorFactory::unary_create(LogicalType::Integer, UnaryOperator::Minus)?;
    Ok(plus_unary_evaluator.unary_eval(&value))
});

let fnck_sql = DataBaseBuilder::path("./data")
    .register_scala_function(TestFunction::new())
    .build()?;
```

### User-Defined Table Function: `features = ["macros"]`
```rust
table_function!(MyTableFunction::test_numbers(LogicalType::Integer) -> [c1: LogicalType::Integer, c2: LogicalType::Integer] => (|v1: DataValue| {
    let num = v1.i32().unwrap();

    Ok(Box::new((0..num)
        .into_iter()
        .map(|i| Ok(Tuple {
            id: None,
            values: vec![
                DataValue::Int32(Some(i)),
                DataValue::Int32(Some(i)),
            ]
        }))) as Box<dyn Iterator<Item = Result<Tuple, DatabaseError>>>)
}));
let fnck_sql = DataBaseBuilder::path("./data")
   .register_table_function(MyTableFunction::new())
   .build()?;
```

### Optimizer
- RBO
- CBO based on RBO(Physical Selection)

### Executor
- Volcano

### MVCC Transaction
- Optimistic

### Field options
- [not] null
- unique
- primary key

### Supports index type
- PrimaryKey
- Unique
- Normal
- Composite

### Supports multiple primary key types
- Tinyint
- UTinyint
- Smallint
- USmallint
- Integer
- UInteger
- Bigint
- UBigint
- Char
- Varchar

### DDL
- Begin (Server only)
- Commit (Server only)
- Rollback (Server only)
- Create
    - [x] Table
    - [x] Index: Unique\Normal\Composite
    - [x] View
- Drop
    - [x] Table
    - [ ] Index
    - [x] View
- Alert
    - [x] Add Column
    - [x] Drop Column
- [x] Truncate

### DQL
- [x] Select
    - SeqScan
    - IndexScan
    - FunctionScan
- [x] Where
- [x] Distinct
- [x] Alias
- [x] Aggregation: 
  - count()
  - sum()
  - avg()
  - min()
  - max()
- [x] SubQuery[select/from/where]
- [x] Join: 
  - Inner
  - Left
  - Right
  - Full
  - Cross (Natural\Using)
- [x] Group By
- [x] Having
- [x] Order By
- [x] Limit
- [x] Show Tables
- [x] Explain
- [x] Describe
- [x] Union

### DML
- [x] Insert
- [x] Insert Overwrite
- [x] Update
- [x] Delete
- [x] Analyze
- [x] Copy To
- [x] Copy From

### DataTypes
- Invalid
- SqlNull
- Boolean
- Tinyint
- UTinyint
- Smallint
- USmallint
- Integer
- UInteger
- Bigint
- UBigint
- Float
- Double
- Char
- Varchar
- Date
- DateTime
- Time
- Tuple