wave4-entity-index-in-query-scatter-pattern

To safely write per-entity results into a NativeArray from a parallel Unity DOTS job, use the [EntityIndexInQuery] attribute to assign each entity a unique, stable index for writing to its own pre-allocated array slot without locks.

The best way to pass data between parallel IJobEntity jobs is a lock-free scatter-gather pattern, where the first job computes results into a shared NativeArray and a downstream job consumes them sequentially.

Out-of-bounds errors during NativeArray scatter occur when the array capacity is not sized exactly to query.CalculateEntityCount(), causing parallel writers to exceed the allocated memory under Burst compilation.

Writing to a shared NativeArray in a parallel IJobEntity does not require locking or atomics if you use [EntityIndexInQuery] to guarantee each entity writes to a unique, stable array slot.

You need to use EntityIndexInQuery for scatter-gather workflows when a parallel IJobEntity must produce per-entity computed results into a pre-allocated NativeArray for a downstream job to consume lock-free.

Limitations of using EntityIndexInQuery include the strict requirement for a unique entity-to-index mapping and accurate NativeArray sizing via CalculateEntityCount, as any mismatch causes out-of-bounds writes under Burst.