Function plan_recursive_value

nodedb-sql/src/planner/cte.rs:160–202

Plan a value-generating WITH RECURSIVE CTE (no collection reference). Produces a `SqlPlan::RecursiveValue` that carries the anchor and step expressions as raw SQL text for evaluation in the Data Plane.

(
    left: &SetExpr,
    right: &SetExpr,
    cte_name: &str,
    declared_columns: &[String],
    distinct: bool,
)

/// Produces a `SqlPlan::RecursiveValue` that carries the anchor and step
/// expressions as raw SQL text for evaluation in the Data Plane.
fn plan_recursive_value(
    left: &SetExpr,
    right: &SetExpr,
    cte_name: &str,
    declared_columns: &[String],
    distinct: bool,
) -> Result<SqlPlan> {
    let init_exprs = extract_select_exprs_as_text(left).ok_or_else(|| SqlError::Parse {
        detail: "WITH RECURSIVE anchor must be a SELECT".into(),
    })?;

    // Validate column count against declared columns list.
    if !declared_columns.is_empty() && init_exprs.len() != declared_columns.len() {
        return Err(SqlError::RecursiveColumnMismatch {
            cte_name: cte_name.to_owned(),
            anchor_cols: init_exprs.len(),
            declared_cols: declared_columns.len(),
        });
    }

    let (step_exprs, condition) =
        extract_step_exprs_and_condition(right).ok_or_else(|| SqlError::Parse {
            detail: "WITH RECURSIVE step must be a SELECT".into(),
        })?;

    // Infer column names from anchor if not declared.
    let columns = if declared_columns.is_empty() {
        // Default column names: col0, col1, ...
        (0..init_exprs.len()).map(|i| format!("col{i}")).collect()
    } else {
        declared_columns.to_vec()
    };

    Ok(SqlPlan::RecursiveValue {
        cte_name: cte_name.to_owned(),
        columns,
        init_exprs,
        step_exprs,
        condition,
        max_depth: DEFAULT_MAX_RECURSION_DEPTH,
        distinct,
    })
}

/// Extract SELECT projection items as raw SQL text strings.
fn extract_select_exprs_as_text(expr: &SetExpr) -> Option<Vec<String>> {