Description

This class holds settings to control how a Parquet file is read by ParquetFileWriter.

Details

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

Unlike the high-level write_parquet, ParquetWriterProperties arguments use the C++ defaults. Currently this means "uncompressed" rather than "snappy" for the compression argument.

Factory

The ParquetWriterProperties$create() factory method instantiates the object and takes the following arguments:

• table: table to write (required)

• version: Parquet version, "1.0" or "2.0". Default "1.0"

• compression: Compression type, algorithm "uncompressed"

• compression_level: Compression level; meaning depends on compression algorithm

• use_dictionary: Specify if we should use dictionary encoding. Default TRUE

• write_statistics: Specify if we should write 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.

See Also

write_parquet

Schema for information about schemas and metadata handling.