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

ManagedQueryBatches

Buffered SQL output whose registry entry and session permit remain live until response serialization explicitly succeeds or fails.

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.

QueryId

QueryStatus

RegisteredQueryGuard

RegisteredSqlQuery

SqlQueryOptions

SqlQueryRegistry

SqlStreamCompletion

Enums

CancelOutcome

CommitFenceOutcome

ExternalBaseWrite

ExternalWriteOp

MongrelQueryError

SqlQueryPhase

Traits

ExternalTable

ExternalTableModule

Functions

contains_boolean_ai_predicate

True when SQL calls a ranked Boolean AI UDF. Remote servers use this to require the bounded scored table functions while embedded sessions retain the trusted Boolean intersection primitives.

Type Aliases

MongrelRecordBatchStream

Result