Module operator 

Volcano-style operator interface for streaming query execution.

This module provides the foundation for a streaming execution model where operators pull rows on-demand rather than materializing everything upfront.

Architecture

┌──────────────┐
│ Consumer     │ ← Pulls rows via next()
└──────┬───────┘
       │
┌──────▼───────┐
│ Join Op      │ ← Build side materialized, probe side streamed
└──────┬───────┘
       │
┌──────┴──────┐
│             │
▼             ▼
┌─────┐   ┌─────┐
│Scan │   │Scan │ ← Stream rows from storage
└─────┘   └─────┘

Key Benefits

1. Reduced Memory: Only materialize what’s needed (e.g., hash join build side)
2. Early Termination: LIMIT can stop execution without processing all rows
3. Pipelining: Multiple operators can work on the same row in sequence
4. Zero-Copy: RowRef allows referencing rows without cloning

Structs

ColumnInfo

Column information for operator schema.

CompositeRow

A composite row that references values from two source rows.

DirectBuildCompositeRow

A direct-build composite row that owns the probe row directly.

EmptyOperator

An empty operator that produces no rows.

JoinProjection

Projection configuration for fused projection during join row creation.

MaterializedOperator

An operator that yields rows from a pre-materialized vector.

ProjectedRow

A projected row whose slots still reference the preceding JOIN edge.

QueryResultOperator

Operator that streams rows from a QueryResult.

SharedRow

Arc-backed reference to one row in a materialized batch.

Enums

ColumnSource

Specifies which side of a binary join a projected column comes from.

OrderingProperty

Physical ordering guaranteed by an operator.

RowRef

A row reference that can be borrowed, owned, or composite.

Traits

Operator

Volcano-style iterator interface for query operators.