Module engine 

Query Execution Engine

Jena-inspired algebraic query execution with pluggable engines.

Architecture

QueryExpr (AST) → Op (Algebra) → Plan → Iterator<Binding>

┌─────────────────────────────────────────────────────────────┐
│                        QueryEngine                          │
├─────────────────────────────────────────────────────────────┤
│  compile(QueryExpr) → Op                                    │
│  optimize(Op) → Op                                          │
│  execute(Op) → BindingIterator                              │
└─────────────────────────────────────────────────────────────┘
                             │
         ┌──────────────────┼──────────────────┐
         ▼                  ▼                  ▼
     OpBGP              OpJoin            OpFilter
  (BasicPattern)     (Join two Ops)    (Filter Op)

Components

• Op: Algebraic operators (scan, filter, join, union, etc.)
• Transform: Visitors that transform Op trees
• Binding: Variable -> Value mapping
• BindingIterator: Lazy result stream
• QueryEngine: Compiles, optimizes, and executes queries

Modules

aggregates_extra

ClickHouse-parity aggregate functions (Track B4 sprint).

binding

Variable Bindings

iterator

Query Result Iterators

op

Algebraic Query Operators

registry

Query Engine Registry

transform

Op Tree Transformations

Structs

Binding

Immutable binding from variables to values

BindingBuilder

Builder for creating bindings

OpBGP

Basic Graph Pattern - set of triple patterns

OpDisjunction

Disjunction operator (OR patterns)

OpDistinct

Distinct operator

OpExtend

Extend operator (bind expression to variable)

OpFilter

Filter operator

OpGroup

Group operator

OpJoin

Join two operators

OpLeftJoin

Left outer join (OPTIONAL)

OpMinus

Minus operator (set difference)

OpNull

Null operator (empty pattern)

OpOrder

Order operator

OpProject

Project operator

OpReduced

Reduced operator (adjacent duplicate removal)

OpSequence

Sequence operator

OpSlice

Slice operator (offset/limit)

OpTable

Table operator (inline data VALUES)

OpTriple

Single triple pattern

OpUnion

Union operator

QueryEngineRegistry

Engine registry

QueryIter

Wrapper for boxed iterator to implement Iterator trait

QueryIterBase

Base query iterator wrapping a binding source

QueryIterFilter

Filter iterator - applies predicate to upstream

QueryIterJoin

Join iterator - nested loop join

QueryIterProject

Project iterator - selects subset of variables

QueryIterSlice

Slice iterator - limit and offset

QueryIterSort

Sort iterator - orders results

QueryIterUnion

Union iterator - concatenates multiple iterators

TransformCopy

Default copy transform (identity transformation)

TransformPushFilter

Filter pushdown transform

Triple

Triple pattern for graph matching

Var

A variable in a query

Enums

Op

Core algebraic operator type

Pattern

Pattern element (variable or concrete value)

Traits

BindingIterator

Core trait for binding iterators

OpTransform

Transformer trait for transforming Op trees

OpVisitor

Visitor trait for walking Op trees (read-only)

QueryEngine

Query engine trait

QueryEngineFactory

Factory for creating query engines