if expression
Ziyang Hu
2 years ago
parent
0e9edd715f
commit
8484ae33a4
@ -0,0 +1,92 @@
|
||||
use std::result;
|
||||
use std::sync::Arc;
|
||||
use crate::data::eval::{EvalError, ExprEvalContext, RowEvalContext};
|
||||
use crate::data::expr::Expr;
|
||||
use crate::data::op::Op;
|
||||
use crate::data::value::Value;
|
||||
|
||||
type Result<T> = result::Result<T, EvalError>;
|
||||
|
||||
pub(crate) struct OpCond;
|
||||
|
||||
pub(crate) struct OpCoalesce;
|
||||
|
||||
impl Op for OpCoalesce {
|
||||
fn arity(&self) -> Option<usize> {
|
||||
None
|
||||
}
|
||||
fn name(&self) -> &str {
|
||||
"~~"
|
||||
}
|
||||
fn non_null_args(&self) -> bool {
|
||||
false
|
||||
}
|
||||
fn eval<'a>(&self, _has_null: bool, args: Vec<Value<'a>>) -> Result<Value<'a>> {
|
||||
for arg in args {
|
||||
if arg != Value::Null {
|
||||
return Ok(arg);
|
||||
}
|
||||
}
|
||||
Ok(Value::Null)
|
||||
}
|
||||
}
|
||||
|
||||
pub(crate) fn row_eval_coalesce<'a, T: RowEvalContext + 'a>(ctx: &'a T, left: &'a Expr<'a>, right: &'a Expr<'a>) -> Result<Value<'a>> {
|
||||
let left = left.row_eval(ctx)?;
|
||||
if left != Value::Null {
|
||||
return Ok(left);
|
||||
}
|
||||
right.row_eval(ctx)
|
||||
}
|
||||
|
||||
const IF_NAME: &str = "if";
|
||||
|
||||
pub(crate) fn partial_eval_coalesce<'a, T: ExprEvalContext + 'a>(ctx: &'a T, args: Vec<Expr<'a>>) -> Result<Expr<'a>> {
|
||||
let mut collected = vec![];
|
||||
for arg in args {
|
||||
match arg.partial_eval(ctx)? {
|
||||
Expr::Const(Value::Null) => {}
|
||||
Expr::Apply(op, args) if op.name() == OpCoalesce.name() => {
|
||||
collected.extend(args);
|
||||
}
|
||||
expr => collected.push(expr)
|
||||
}
|
||||
}
|
||||
Ok(match collected.len() {
|
||||
0 => Expr::Const(Value::Null),
|
||||
1 => collected.pop().unwrap(),
|
||||
_ => Expr::Apply(Arc::new(OpCoalesce), collected)
|
||||
})
|
||||
}
|
||||
|
||||
pub(crate) fn row_eval_if_expr<'a, T: RowEvalContext + 'a>(ctx: &'a T, cond: &'a Expr<'a>, if_part: &'a Expr<'a>, else_part: &'a Expr<'a>) -> Result<Value<'a>> {
|
||||
let cond = cond.row_eval(ctx)?;
|
||||
match cond {
|
||||
Value::Bool(b) => {
|
||||
Ok(if b {
|
||||
if_part.row_eval(ctx)?
|
||||
} else {
|
||||
else_part.row_eval(ctx)?
|
||||
})
|
||||
}
|
||||
Value::Null => Ok(Value::Null),
|
||||
v => Err(EvalError::OpTypeMismatch(IF_NAME.to_string(), vec![v.to_static()]))
|
||||
}
|
||||
}
|
||||
|
||||
pub(crate) fn partial_eval_if_expr<'a, T: ExprEvalContext + 'a>(ctx: &'a T, cond: Expr<'a>, if_part: Expr<'a>, else_part: Expr<'a>) -> Result<Expr<'a>> {
|
||||
let cond = cond.partial_eval(ctx)?;
|
||||
match cond {
|
||||
Expr::Const(Value::Null) => Ok(Expr::Const(Value::Null)),
|
||||
Expr::Const(Value::Bool(b)) => {
|
||||
Ok(if b {
|
||||
if_part.partial_eval(ctx)?
|
||||
} else {
|
||||
else_part.partial_eval(ctx)?
|
||||
})
|
||||
}
|
||||
cond => {
|
||||
Ok(Expr::IfExpr((cond, if_part.partial_eval(ctx)?, else_part.partial_eval(ctx)?).into()))
|
||||
}
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue