Barrier

Wait for preceding branches before downstream work begins.

Barrier is an explicit synchronization point. Every node before the barrier must finish before a following node may begin.

version.arrange(
    Scatter((extract-products, extract-support-tickets)),
    Barrier(),
    join-products-to-tickets,
)

When to use it

Use a barrier when downstream work requires complete results from several otherwise independent branches. Data dependencies already impose their own order; do not add barriers between ordinary producer and consumer tasks.

Output

A barrier produces no rows and changes no Space. It only constrains execution order.