Crate mongreldb_query 

DataFusion SQL + Arrow frontend for MongrelDB.

MongrelProvider implements DataFusion’s TableProvider: each scan() takes an MVCC snapshot of the table, materializes the visible columns, and hands DataFusion a streaming MongrelScanExec (see scan.rs) that emits one RecordBatch per 65 536-row chunk. DataFusion then runs the SQL — projection, filter, aggregation, limit — with its own vectorized kernels, pipelined across those small batches so a LIMIT short-circuits and peak memory stays bounded. MongrelDB owns storage/writes/indexes; DataFusion owns the vectorized execution.

Example (skipped from doctests; see tests/sql.rs for runnable ones):

let db = Table::create("travel.mongreldb", /* schema */ unimplemented!(), 1)?;
let session = MongrelSession::new(db);
session.register("travel_trips").await?;
let batches = session.run("select * from travel_trips where cost < 300").await?;

Modules

arrow_conv

MongrelDB ↔ Arrow conversions: schema mapping and Vec<Row> → RecordBatch.

extended_sql_functions

Extended SQL Functions: application-oriented scalar functions layered on DataFusion for date/time, JSON, string, and math compatibility.

Structs

ExternalModuleDescriptor

ExternalModuleIndex

ExternalModuleRegistry

ExternalPlan

ExternalPlanRequest

ExternalScan

ExternalTxn

ExternalWriteResult

ModuleConnectCtx

MongrelProvider

A MongrelDB table exposed to DataFusion. Holds the live Table behind a mutex; each scan takes a fresh MVCC snapshot.

MongrelSession

Convenience wrapper: a DataFusion SessionContext bound to a live MongrelDB, with a result cache keyed by (sql, snapshot_epoch) that auto-invalidates when a commit advances the epoch.

Enums

ExternalBaseWrite

ExternalWriteOp

MongrelQueryError

Traits

ExternalTable

ExternalTableModule

Type Aliases

Result