30 lines
938 B
Rust
30 lines
938 B
Rust
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//! Atom operator: scan a [`Table`] under an [`AtomPattern`] and return a
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//! binding [`Relation`].
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//!
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//! An atom pattern specifies, for each table column, either a variable to bind
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//! or a literal that the cell must equal. A variable appearing in more than one
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//! column forces those cells to be equal (so `Edge(X, X)` keeps only
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//! self-loops). The output relation has one column per distinct variable, in
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//! first-occurrence order.
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use crate::{relation::Relation, table::Table, value::Value};
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub enum Term {
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Var(String),
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Lit(Value),
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}
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#[derive(Debug, Clone)]
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pub struct AtomPattern {
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pub columns: Vec<Term>,
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}
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#[must_use]
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pub fn scan_atom(_table: &Table, _pattern: &AtomPattern) -> Relation {
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todo!(
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"scan rows, filter by repeated-variable equality and literal equality, \
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project to one column per distinct variable in first-occurrence order"
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)
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}
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