Method check_subquery_exists

graphlite/src/exec/executor.rs:1065–1083

Check if a subquery returns any results (optimized for EXISTS) Returns true as soon as the first result is found, without materializing all results

(
        &self,
        query: &crate::ast::Query,
        context: &ExecutionContext,
    )

    /// Check if a subquery returns any results (optimized for EXISTS)
    /// Returns true as soon as the first result is found, without materializing all results
    fn check_subquery_exists(
        &self,
        query: &crate::ast::Query,
        context: &ExecutionContext,
    ) -> Result<bool, ExecutionError> {
        use crate::ast::Query;
        match query {
            Query::Basic(basic_query) => {
                // For basic queries, check existence with early termination
                self.check_basic_query_exists(basic_query, context)
            }
            _ => {
                // For complex queries (set operations, limited queries), fall back to full execution
                // TODO: These could also be optimized for early termination in the future
                let result = self.execute_subquery_with_context(query, context)?;
                Ok(!result.rows.is_empty())
            }
        }
    }

    /// Check if a basic query returns any results with early termination
    fn check_basic_query_exists(