toasty_core/stmt/
condition.rs

1use crate::stmt::{Expr, Node, Statement, Visit, VisitMut};
2
3/// A guard condition on an [`Update`](super::Update) statement.
4///
5/// Unlike a [`Filter`](super::Filter), a condition does not select which rows
6/// to operate on. Instead, it is evaluated after the filter and determines
7/// whether the update should actually be applied. If the condition is not met,
8/// the update is silently skipped.
9///
10/// When `expr` is `None`, no condition is applied (the update always proceeds).
11///
12/// # Examples
13///
14/// ```
15/// use toasty_core::stmt::Condition;
16///
17/// let cond = Condition::default();
18/// assert!(cond.is_none());
19/// ```
20#[derive(Debug, Default, Clone, PartialEq)]
21pub struct Condition {
22    /// The condition expression, or `None` for unconditional updates.
23    pub expr: Option<Expr>,
24}
25
26impl Condition {
27    /// Creates a condition from an expression.
28    pub fn new(expr: impl Into<Expr>) -> Condition {
29        Condition {
30            expr: Some(expr.into()),
31        }
32    }
33
34    /// Returns `true` if a condition expression is set.
35    pub fn is_some(&self) -> bool {
36        self.expr.is_some()
37    }
38
39    /// Returns `true` if no condition expression is set.
40    pub fn is_none(&self) -> bool {
41        self.expr.is_none()
42    }
43}
44
45impl Statement {
46    /// Returns a reference to this statement's condition, if it has one and it
47    /// is set. Only `Update` statements support conditions.
48    pub fn condition(&self) -> Option<&Condition> {
49        match self {
50            Statement::Update(update) if update.condition.is_some() => Some(&update.condition),
51            _ => None,
52        }
53    }
54
55    /// Returns a mutable reference to the statement's condition.
56    ///
57    /// Returns `None` for statements that do not support conditions.
58    pub fn condition_mut(&mut self) -> Option<&mut Condition> {
59        match self {
60            Statement::Update(update) => Some(&mut update.condition),
61            _ => None,
62        }
63    }
64
65    /// Returns a mutable reference to the statement's condition.
66    ///
67    /// # Panics
68    ///
69    /// Panics if the statement does not support conditions.
70    #[track_caller]
71    pub fn condition_mut_unwrap(&mut self) -> &mut Condition {
72        match self {
73            Statement::Update(update) => &mut update.condition,
74            _ => panic!("expected Statement with condition"),
75        }
76    }
77}
78
79impl Node for Condition {
80    fn visit<V: Visit>(&self, mut visit: V) {
81        visit.visit_condition(self);
82    }
83
84    fn visit_mut<V: VisitMut>(&mut self, mut visit: V) {
85        visit.visit_condition_mut(self);
86    }
87}
88
89impl<T> From<T> for Condition
90where
91    Expr: From<T>,
92{
93    fn from(value: T) -> Self {
94        Condition {
95            expr: Some(value.into()),
96        }
97    }
98}
toasty_core/stmt/condition.rs

toasty_core/stmt/
condition.rs
