Function fold_function_call

nodedb-sql/src/planner/const_fold.rs:214–237

Fold a function call by recursively folding its arguments, dispatching through the shared scalar evaluator, and converting the result back to `SqlValue`. Only folds functions that are present in `registry`, so callers can distinguish "unknown function" from "known function, all args folded".

(
    name: &str,
    args: &[SqlExpr],
    registry: &FunctionRegistry,
)

/// callers can distinguish "unknown function" from "known function, all
/// args folded".
pub fn fold_function_call(
    name: &str,
    args: &[SqlExpr],
    registry: &FunctionRegistry,
) -> Option<SqlValue> {
    // Gate on registry so unknown-function paths keep their existing
    // fallbacks instead of collapsing to SqlValue::Null. Aggregates and
    // window functions aren't foldable — they need a row stream.
    let meta = registry.lookup(name)?;
    if matches!(
        meta.category,
        FunctionCategory::Aggregate | FunctionCategory::Window
    ) {
        return None;
    }

    let folded_args: Vec<Value> = args
        .iter()
        .map(|a| fold_constant(a, registry).map(sql_to_ndb_value))
        .collect::<Option<_>>()?;

    let result = nodedb_query::functions::eval_function(&name.to_lowercase(), &folded_args);
    Some(ndb_to_sql_value(result))
}

fn sql_to_ndb_value(v: SqlValue) -> Value {
    match v {