jonahgao commented on code in PR #13028:
URL: https://github.com/apache/datafusion/pull/13028#discussion_r1812109755
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datafusion/expr/src/logical_plan/plan.rs:
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@@ -2799,14 +2817,71 @@ impl PartialOrd for Extension {
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Hash)]
pub struct Limit {
/// Number of rows to skip before fetch
- pub skip: usize,
+ pub skip: Option<Box<Expr>>,
/// Maximum number of rows to fetch,
/// None means fetching all rows
- pub fetch: Option<usize>,
+ pub fetch: Option<Box<Expr>>,
/// The logical plan
pub input: Arc<LogicalPlan>,
}
+/// Different types of skip expression in Limit plan.
+pub enum SkipType {
+ /// The skip expression is a literal value.
+ Literal(usize),
+ /// Currently only supports expressions that can be folded into constants.
+ UnsupportedExpr,
Review Comment:
Constant folding requires the `TypeCoercion` and `SimplifyExpressions` rule.
We can't directly invoke them during planning for now and need to defer them to
optimizer.
Another reason the Limit node needs to contain expressions is to support
Prepare statements. Issue #12294 requires the Limit node to use
`Expr::Placeholder`.
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