Module executor 

Unified Volcano Query Executor (v1.0)

Single pipeline for all SQL execution:

SQL Text → Parser → AST → Planner → Volcano Operator Tree → Row-at-a-time → Result

Architecture

All operators implement the PlanNode trait (Volcano iterator model):

trait PlanNode {
    fn schema(&self) -> &Schema;
    fn next(&mut self) -> Result<Option<Row>>;
}

Operators form a tree: each next() call pulls one row from its children, processes it, and returns the result. This enables streaming execution with minimal memory footprint.

Operators

Operator	Description
SeqScan	Full table scan via StorageBackend
IndexSeek	Index-based lookup via StorageBackend
Filter	Predicate evaluation (WHERE)
Project	Column selection + expression eval
Sort	In-memory sort (materializing)
Limit	LIMIT + OFFSET
HashJoin	Hash-based equi-join
NestedLoopJoin	Nested loop join (theta joins)
MergeJoin	Merge join on sorted inputs
HashAggregate	GROUP BY + aggregate functions
Explain	EXPLAIN plan output
Values	Inline VALUES (…) rows
Empty	Returns no rows

Re-exports

pub use types::Row;

pub use types::Schema;

pub use types::ColumnMeta;

pub use node::PlanNode;

pub use eval::eval_expr;

pub use eval::eval_predicate;

pub use scan::SeqScanNode;

pub use scan::IndexSeekNode;

pub use filter::FilterNode;

pub use project::ProjectNode;

pub use sort::SortNode;

pub use limit::LimitNode;

pub use join::HashJoinNode;

pub use join::NestedLoopJoinNode;

pub use join::MergeJoinNode;

pub use aggregate::HashAggregateNode;

pub use explain::ExplainNode;

pub use planner::QueryPlanner;

pub use pipeline::execute_sql;

pub use pipeline::execute_statement;

pub use pipeline::ExecutorConfig;

Modules

aggregate

Hash aggregate operator (GROUP BY + aggregate functions).

eval

SQL expression evaluator over Volcano rows.

explain

EXPLAIN operator — generates query plan description as rows.

filter

Filter operator (WHERE clause).

join

Join operators: HashJoin, NestedLoopJoin, MergeJoin.

limit

Limit + Offset operator.

node

Volcano iterator model trait.

pipeline

Unified execution pipeline: SQL text → result.

planner

Query planner: SQL AST → Volcano operator tree.

project

Project operator (column selection and expression evaluation).

scan

Table scan and index seek operators.

sort

Sort operator.

types

Core types for the Volcano executor.