sqlalchemy.engine.cursor.BufferedRowCursorFetchStrategy

A cursor fetch strategy with row buffering behavior.

This strategy buffers the contents of a selection of rows before fetchone() is called. This is to allow the results of cursor.description to be available immediately, when interfacing with a DB-API that requires rows to be consumed before this information is available (currently psycopg2, when used with server-side cursors).

The pre-fetching behavior fetches only one row initially, and then grows its buffer size by a fixed amount with each successive need for additional rows up the max_row_buffer size, which defaults to 1000:

with psycopg2_engine.connect() as conn:

    result = conn.execution_options(
        stream_results=True, max_row_buffer=50
        ).execute(text("select * from table"))