backend-duckdb function

DuckDB SQL backend for dbplyr

This is a SQL backend for dbplyr tailored to take into account DuckDB's possibilities. This mainly follows the backend for PostgreSQL, but contains more mapped functions.

tbl_file() is an experimental variant of dplyr::tbl() to directly access files on disk. It is safer than dplyr::tbl() because there is no risk of misinterpreting the request, and paths with special characters are supported.

tbl_function() is an experimental variant of dplyr::tbl()

to create a lazy table from a table-generating function, useful for reading nonstandard CSV files or other data sources. It is safer than dplyr::tbl() because there is no risk of misinterpreting the query. See https://duckdb.org/docs/data/overview for details on data importing functions.

As an alternative, use dplyr::tbl(src, dplyr::sql("SELECT ... FROM ...")) for custom SQL queries.

tbl_query() is deprecated in favor of tbl_function().

Use simulate_duckdb() with lazy_frame()

to see simulated SQL without opening a DuckDB connection.

tbl_file(src, path, ..., cache = FALSE)

tbl_function(src, query, ..., cache = FALSE)

tbl_query(src, query, ...)

simulate_duckdb(...)

Arguments

• src: A duckdb connection object
• path: Path to existing Parquet, CSV or JSON file
• ...: Any parameters to be forwarded
• cache: Enable object cache for Parquet files
• query: SQL code, omitting the FROM clause

Examples

library(dplyr, warn.conflicts = FALSE)
con <- DBI::dbConnect(duckdb(), path = ":memory:")

db <- copy_to(con, data.frame(a = 1:3, b = letters[2:4]))

db %>%
  filter(a > 1) %>%
  select(b)

path <- tempfile(fileext = ".csv")
write.csv(data.frame(a = 1:3, b = letters[2:4]))

db_csv <- tbl_file(con, path)
db_csv %>%
  summarize(sum_a = sum(a))

db_csv_fun <- tbl_function(con, paste0("read_csv_auto('", path, "')"))
db_csv %>%
  count()

DBI::dbDisconnect(con, shutdown = TRUE)