bustubx 0.3.0

A simple relational database written in Rust
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

use crate::catalog::Schema;
use crate::catalog::{Column, DataType};
use crate::common::ScalarValue;
use crate::error::BustubxResult;
use crate::expression::{Expr, ExprTrait};
use crate::storage::Tuple;

#[derive(Clone, PartialEq, Eq, Debug)]
pub struct Alias {
    pub expr: Box<Expr>,
    pub name: String,
}

impl ExprTrait for Alias {
    fn data_type(&self, input_schema: &Schema) -> BustubxResult<DataType> {
        self.expr.data_type(input_schema)
    }

    fn nullable(&self, input_schema: &Schema) -> BustubxResult<bool> {
        self.expr.nullable(input_schema)
    }

    fn evaluate(&self, tuple: &Tuple) -> BustubxResult<ScalarValue> {
        self.expr.evaluate(tuple)
    }

    fn to_column(&self, input_schema: &Schema) -> BustubxResult<Column> {
        Ok(Column::new(
            self.name.clone(),
            self.data_type(input_schema)?,
            self.nullable(input_schema)?,
        ))
    }
}

impl std::fmt::Display for Alias {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{} AS {}", self.expr, self.name)
    }
}