Stream a DuckDB query as native data-frame batches

Opens a native DuckDB streaming result through the Rducks extension and returns the rows in DuckDB-sized batches as data frames, instead of an eager DBI::dbGetQuery() result. Each batch is materialized directly from DuckDB vectors to R values on the recorded R thread. The stream uses the extension's database-scoped connection, so it cannot see caller-connection temporary tables or views.

Usage

rducks_query_stream(con, sql)

Arguments

con

A duckdb_connection with Rducks enabled.

sql

A non-empty SQL query string.

Value

An object of class rducks_query_stream with $next_batch() (returns the next data-frame batch, or NULL at end of stream), $close(), $schema (column names and Rducks type tokens), and $token. The stream closes on $close() or rducks_release(con).

Examples

# \donttest{
db <- duckdb::dbConnect(duckdb::duckdb(config = list(allow_unsigned_extensions = "true")))
#> duckdb keeps downloaded extensions and secrets in a temporary directory:
#> ℹ /tmp/Rtmp7iTOSm/duckdb
#> This is removed when the R session ends.
#> • Extensions are re-downloaded each session.
#> • Secrets are lost.
#> ℹ Run duckdb(shared_home = TRUE) (or create ~/.duckdb) to keep them (suitable for most users).
#> ℹ Run duckdb(shared_home = FALSE) to accept the temporary directory (and silence this message).
#> ℹ See ?duckdb_storage for details and alternatives.
rducks_enable(db, threads = "single")
stream <- rducks_query_stream(db, "SELECT i::INTEGER AS i FROM range(1, 6) t(i)")
stream$next_batch()
#>   i
#> 1 1
#> 2 2
#> 3 3
#> 4 4
#> 5 5
stream$close()
rducks_release(db)
DBI::dbDisconnect(db, shutdown = TRUE)
# }