Module changelog 

Changelog and Retraction Support

Z-set style changelog records with integer weights for incremental computation. This is the foundation for exactly-once sinks, cascading materialized views, and CDC connectors.

Key Concepts

• Z-sets: Elements have integer weights. Weight > 0 → insert, weight < 0 → delete.
• Retraction: Emitting (-old, +new) pairs to correct previous results.
• CDC Envelope: Debezium-compatible format for downstream systems.

Ring Architecture

• Ring 0: ChangelogRef and ChangelogBuffer for zero-allocation hot path
• Ring 1: LateDataRetractionGenerator and CdcEnvelope serialization
• Ring 2: Changelog configuration and CDC format selection

Example

use laminar_core::operator::changelog::{
    ChangelogBuffer, ChangelogRef, RetractableCountAccumulator,
    RetractableAccumulator, CdcEnvelope, CdcSource,
};
use laminar_core::operator::window::CdcOperation;

// Ring 0: Zero-allocation changelog tracking
let mut buffer = ChangelogBuffer::with_capacity(1024);
buffer.push(ChangelogRef::insert(0, 0));
buffer.push(ChangelogRef::delete(0, 1));

// Ring 1: Retractable aggregation
let mut agg = RetractableCountAccumulator::default();
agg.add(());
agg.add(());
assert_eq!(agg.result(), 2);
agg.retract(&());
assert_eq!(agg.result(), 1);

// CDC envelope for sinks
let source = CdcSource::new("laminardb", "default", "orders");
let envelope = CdcEnvelope::insert(serde_json::json!({"id": 1}), source, 1000);

Structs

ArchivedRetractableAvgAccumulator

An archived RetractableAvgAccumulator

ArchivedRetractableCountAccumulator

An archived RetractableCountAccumulator

ArchivedRetractableSumAccumulator

An archived RetractableSumAccumulator

CdcEnvelope

CDC envelope for sink serialization.

CdcSource

Source metadata for CDC envelope.

ChangelogBuffer

Ring 0 changelog buffer (pre-allocated, reused per epoch).

ChangelogRef

Zero-allocation changelog reference for Ring 0 hot path.

LateDataRetractionGenerator

Generates retractions for late data corrections.

RetractableAvgAccumulator

Retractable average accumulator.

RetractableAvgAccumulatorResolver

The resolver for an archived RetractableAvgAccumulator

RetractableCountAccumulator

Retractable count accumulator.

RetractableCountAccumulatorResolver

The resolver for an archived RetractableCountAccumulator

RetractableFirstValueAccumulator

Retractable FIRST_VALUE accumulator for changelog/retraction mode.

RetractableFirstValueF64Accumulator

Retractable FIRST_VALUE accumulator for f64 values.

RetractableLastValueAccumulator

Retractable LAST_VALUE accumulator for changelog/retraction mode.

RetractableLastValueF64Accumulator

Retractable LAST_VALUE accumulator for f64 values.

RetractableMaxAccumulator

Retractable max accumulator with counted value tracking.

RetractableMinAccumulator

Retractable min accumulator with counted value tracking.

RetractableSumAccumulator

Retractable sum accumulator.

RetractableSumAccumulatorResolver

The resolver for an archived RetractableSumAccumulator

Traits

RetractableAccumulator

Extension trait for accumulators that support retractions.