Module stream 

Bounded-memory streaming reads — the native-cursor counterpart to the eager Connection::query.

query materializes the whole result into a Vec<Row>, which is fine for the CLI table view but unusable for an embedder ingesting a multi-million-row table under a fixed memory budget. RowCursor pulls rows from a native driver cursor one bounded batch at a time, so peak resident memory is O(batch + cap) rather than O(total rows).

Bounded-memory model. Every backend drives a row producer that is back-pressured: the async network drivers (tokio-postgres query_raw, mysql_async query_iter, tiberius QueryStream) expose a native row stream that only fetches more from the server as the consumer pulls; the synchronous drivers (rusqlite, ODPI-C oracle) run their row-stepping loop on a spawn_blocking thread that feeds a bounded tokio::sync::mpsc channel — the producer blocks on blocking_send once cap rows are in flight, so at most cap rows are ever buffered ahead of the consumer. Either way no code path collects the full result.

Blocking model. RowCursor borrows its connection’s private current-thread runtime; each next_batch / Iterator::next call drives the producer with block_on, blocking the calling thread until the next row(s) arrive. The same current-thread reentrancy rule as Connection applies — never pull from a cursor inside another block_on on the same thread.

Size guards. Each decoded row is checked against the connection’s per-cell / per-row SizeGuards before it is retained, so a pathological cell fails fast with a structured error rather than OOMing a streaming ingest.

Structs

RowCursor

A streaming read handle over a native database cursor.

Constants

DEFAULT_CURSOR_CAPACITY

Default number of rows a streaming cursor keeps in flight between the producer and the consumer. Caps the bounded channel for the synchronous (spawn_blocking) backends and the default next_batch chunk; the async backends are additionally bounded by the driver’s own server-side fetch window.

Type Aliases

BoxRowStream

A boxed, backend-erased stream of decoded rows.