bigrquery: bq_table_download – R documentation

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bq_table_download

Download table data

Description

This retrieves rows in chunks of page_size. It is most suitable for results of smaller queries (<100 MB, say). For larger queries, it is better to export the results to a CSV file stored on google cloud and use the bq command line tool to download locally.

Usage

bq_table_download(
  x,
  max_results = Inf,
  page_size = 10000,
  start_index = 0L,
  max_connections = 6L,
  quiet = NA,
  bigint = c("integer", "integer64", "numeric", "character")
)

Arguments

`x`	A bq_table
`max_results`	Maximum number of results to retrieve. Use `Inf` retrieve all rows.
`page_size`	The number of rows returned per page. Make this smaller if you have many fields or large records and you are seeing a 'responseTooLarge' error.
`start_index`	Starting row index (zero-based).
`max_connections`	Number of maximum simultaneously connections to BigQuery servers.
`quiet`	If `FALSE`, displays progress bar; if `TRUE` is silent; if `NA` displays progress bar only for long-running jobs.
`bigint`	The R type that BigQuery's 64-bit integer types should be mapped to. The default is `"integer"` which returns R's `integer` type but results in `NA` for values above/below +/- 2147483647. `"integer64"` returns a bit64::integer64, which allows the full range of 64 bit integers.

Value

Because data retrieval may generalise list-cols and the data frame print method can have problems with list-cols, this method returns tibbles. If you need a data frame, coerce the results with as.data.frame().

Complex data

bigrquery will retrieve nested and repeated columns in to list-columns as follows:

Repeated values (arrays) will become a list-cols of vectors.
Records will become list-cols of named lists.
Repeated records will become list-cols of data frames.

Larger datasets

In my timings, this code takes around 1 minute per 100 MB of data. If you need to download considerably more than this, I recommend:

Export a .csv file to Cloud Storage using bq_table_save()
Use the gsutil command line utility to download it
Read the csv file into R with readr::read_csv() or data.table::fread().

Unfortunately you can not export nested or repeated formats into CSV, and the formats that BigQuery supports (arvn and ndjson) that allow for nested/repeated values, are not well supported in R.

API documentation

list

Examples

if (bq_testable()) {
df <- bq_table_download("publicdata.samples.natality", max_results = 35000)
}

bigrquery

An Interface to Google's 'BigQuery' 'API'

v1.3.2

GPL-3

Authors

Hadley Wickham [aut, cre] (<https://orcid.org/0000-0003-4757-117X>), Jennifer Bryan [aut] (<https://orcid.org/0000-0002-6983-2759>), Kungliga Tekniska Högskolan [ctb] (strptime implementation), The NetBSD Foundation, Inc. [ctb] (gmtime implementation), RStudio [cph, fnd]

Initial release