Struct BroadcastRuntimeRule 

pub struct BroadcastRuntimeRule { /* private fields */ }

AQE rule that promotes or demotes broadcast joins based on the observed output size from the previous execution.

BroadcastAutoRule makes a logical-time guess from estimated_rows; this rule corrects that guess at runtime:

• Promotion: when the observed stage output is at or below max_broadcast_bytes and a node is broadcast_eligible() with Hash or RoundRobin partitioning, the node’s partitioning is rewritten to Partitioning::Broadcast, replacing the shuffle with a replicate.
• Demotion: when a node is already Partitioning::Broadcast but the observed output exceeds the threshold, the broadcast is undone. Partitioning::Broadcast does not record the original hash keys, so they cannot be recovered; the node is demoted to Partitioning::RoundRobin { buckets } with buckets = clamp(ceil(observed / 128 MiB), 2, 64). Round-robin is the semantically safe choice — it makes no key-colocation promise, whereas guessing hash keys could silently mis-distribute keyed data.

Like the other AQE sizing rules, the observed size is the sum over the per-stage RuntimeStats slice, preferring serialized_bytes (shuffle wire size) and falling back to memory_bytes when it is zero — the same convention as AutoPartitionRule.

The rule is intrinsically disabled for streaming plans (changing partitioning mid-job would orphan keyed state) and returns None when stats are empty or nothing changes.

Implementations

impl BroadcastRuntimeRule

pub fn new(max_broadcast_bytes: u64) -> Self

Create a new rule with the given broadcast size threshold in bytes.

Use DEFAULT_MAX_BROADCAST_BYTES (64 MiB) for the standard default.

Trait Implementations

impl AqeRule for BroadcastRuntimeRule

fn name(&self) -> &str

Short, stable rule name used in explain and diagnostics output.

fn apply( &self, plan: &PhysicalPlan, stats: &[RuntimeStats], ) -> Option<PhysicalPlan>

Apply the AQE rule given collected RuntimeStats for each stage.