Function split_equality_from_expr

nodedb-sql/src/engine_rules/mod.rs:316–335

Return `(column, literal, residual_expr)` for an equality found anywhere in a right-leaning AND conjunction tree, or `None` if no bare column-equals-literal predicate exists. The residual preserves every sibling conjunct in their original order; `None` means the expression was a bare equality with nothing left behind.

(expr: &SqlExpr)

/// every sibling conjunct in their original order; `None` means the
/// expression was a bare equality with nothing left behind.
fn split_equality_from_expr(expr: &SqlExpr) -> Option<(String, SqlValue, Option<SqlExpr>)> {
    // Gather the conjuncts of a top-level AND chain left-to-right.
    let mut conjuncts: Vec<SqlExpr> = Vec::new();
    flatten_and(expr, &mut conjuncts);

    // Find the first conjunct that is a bare column-equals-literal.
    let eq_idx = conjuncts.iter().position(is_column_eq_literal)?;
    let eq = conjuncts.remove(eq_idx);
    let (col, lit) = match eq {
        SqlExpr::BinaryOp { left, op, right } => match (*left, op, *right) {
            (SqlExpr::Column { name, .. }, BinaryOp::Eq, SqlExpr::Literal(v)) => (name, v),
            (SqlExpr::Literal(v), BinaryOp::Eq, SqlExpr::Column { name, .. }) => (name, v),
            _ => return None,
        },
        _ => return None,
    };

    let residual = rebuild_and(conjuncts);
    Some((col, lit, residual))
}

/// Append every leaf of a right-leaning `AND` tree to `out`. Non-AND
/// expressions are a single leaf.