write_parquet {arrow}

Write Parquet file to disk

Description

Parquet is a columnar storage file format. This function enables you to write Parquet files from R.

Usage

write_parquet(
  x,
  sink,
  chunk_size = NULL,
  version = "2.4",
  compression = default_parquet_compression(),
  compression_level = NULL,
  use_dictionary = NULL,
  write_statistics = NULL,
  data_page_size = NULL,
  use_deprecated_int96_timestamps = FALSE,
  coerce_timestamps = NULL,
  allow_truncated_timestamps = FALSE
)

Arguments

x

data.frame, RecordBatch, or Table

sink

A string file path, connection, URI, or OutputStream, or path in a file system (SubTreeFileSystem)

chunk_size

how many rows of data to write to disk at once. This directly corresponds to how many rows will be in each row group in parquet. If NULL, a best guess will be made for optimal size (based on the number of columns and number of rows), though if the data has fewer than 250 million cells (rows x cols), then the total number of rows is used.

version

parquet version: "1.0", "2.0" (deprecated), "2.4" (default), "2.6", or "latest" (currently equivalent to 2.6). Numeric values are coerced to character.

compression

compression algorithm. Default "snappy". See details.

compression_level

compression level. Meaning depends on compression algorithm

use_dictionary

logical: use dictionary encoding? Default TRUE

write_statistics

logical: include statistics? Default TRUE

data_page_size

Set a target threshold for the approximate encoded size of data pages within a column chunk (in bytes). Default 1 MiB.

use_deprecated_int96_timestamps

logical: write timestamps to INT96 Parquet format, which has been deprecated? Default FALSE.

coerce_timestamps

Cast timestamps a particular resolution. Can be NULL, "ms" or "us". Default NULL (no casting)

allow_truncated_timestamps

logical: Allow loss of data when coercing timestamps to a particular resolution. E.g. if microsecond or nanosecond data is lost when coercing to "ms", do not raise an exception. Default FALSE.

Details

Due to features of the format, Parquet files cannot be appended to. If you want to use the Parquet format but also want the ability to extend your dataset, you can write to additional Parquet files and then treat the whole directory of files as a Dataset you can query. See the dataset article for examples of this.

The parameters compression, compression_level, use_dictionary and write_statistics support various patterns:

• The default NULL leaves the parameter unspecified, and the C++ library uses an appropriate default for each column (defaults listed above)

• A single, unnamed, value (e.g. a single string for compression) applies to all columns

• An unnamed vector, of the same size as the number of columns, to specify a value for each column, in positional order

• A named vector, to specify the value for the named columns, the default value for the setting is used when not supplied

The compression argument can be any of the following (case-insensitive): "uncompressed", "snappy", "gzip", "brotli", "zstd", "lz4", "lzo" or "bz2". Only "uncompressed" is guaranteed to be available, but "snappy" and "gzip" are almost always included. See codec_is_available(). The default "snappy" is used if available, otherwise "uncompressed". To disable compression, set compression = "uncompressed". Note that "uncompressed" columns may still have dictionary encoding.

Value

the input x invisibly.

See Also

ParquetFileWriter for a lower-level interface to Parquet writing.

Examples

tf1 <- tempfile(fileext = ".parquet")
write_parquet(data.frame(x = 1:5), tf1)

# using compression
if (codec_is_available("gzip")) {
  tf2 <- tempfile(fileext = ".gz.parquet")
  write_parquet(data.frame(x = 1:5), tf2, compression = "gzip", compression_level = 5)
}