export generate_tpch (#112)

* export generate_tpch

* expand description

* Update R/ensure-tpch-source.R

Co-authored-by: Jonathan Keane <jkeane@gmail.com>

* update README

* render docs

Co-authored-by: Jonathan Keane <jkeane@gmail.com>

NAMESPACE

@@ -17,6 +17,7 @@ export(ensure_dataset)
 export(ensure_format)
 export(ensure_source)
 export(file_with_ext)
+export(generate_tpch)
 export(get_csv_reader)
 export(get_csv_writer)
 export(get_dataset_attr)

R/ensure-tpch-source.R

@@ -4,6 +4,21 @@
 #' @export
 tpch_tables <- c("customer", "lineitem", "nation", "orders", "part", "partsupp", "region", "supplier")
 
+#' Generate tpch data
+#'
+#' Generate tpch data at a given scale factor. By default,
+#' data is output relative to the current working directory. However,
+#' you can set the environment variable `ARROWBENCH_DATA_DIR` to
+#' point to another directory. Setting this environment variable has
+#' the advantage of being a central location for general usage. Running
+#' this function will install a custom version of duckdb in an `r_libs`
+#' directory, relative to the directory specified by the environment
+#' variable `ARROWBENCH_LOCAL_DIR`. When running this function for the first time you will
+#' see significant output from that installation process. This is normal.
+#'
+#' @param scale_factor a relative measure of the size of data in gigabytes.
+#'
+#' @export
 generate_tpch <- function(scale_factor = 1) {
   # Ensure that we have our custom duckdb that has the TPC-H extension built.
   ensure_custom_duckdb()

README.md

@@ -256,7 +256,8 @@ Source files are cached in a `data` directory and are only downloaded if
 not present. This speeds up repeat benchmark runs on the same host. By default,
 `data` is assumed to be relative to the current working directory, but
 you can set the environment variable `ARROWBENCH_DATA_DIR` to point to another 
-(permanent) base directory.
+base directory. Setting this environment variable has the advantage of being a 
+central location for general usage.
 
 Similarly, there is an `ensure_lib()` function called in the `global_setup()`
 that supports a list of known `arrow` package versions, which are mapped to