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arrow (version 8.0.0)

ParquetFileReader: ParquetFileReader class

Description

This class enables you to interact with Parquet files.

Arguments

Factory

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

  • file A character file name, raw vector, or Arrow file connection object (e.g. RandomAccessFile).

  • props Optional ParquetArrowReaderProperties

  • mmap Logical: whether to memory-map the file (default TRUE)

  • ... Additional arguments, currently ignored

Methods

  • $ReadTable(column_indices): get an arrow::Table from the file. The optional column_indices= argument is a 0-based integer vector indicating which columns to retain.

  • $ReadRowGroup(i, column_indices): get an arrow::Table by reading the ith row group (0-based). The optional column_indices= argument is a 0-based integer vector indicating which columns to retain.

  • $ReadRowGroups(row_groups, column_indices): get an arrow::Table by reading several row groups (0-based integers). The optional column_indices= argument is a 0-based integer vector indicating which columns to retain.

  • $GetSchema(): get the arrow::Schema of the data in the file

  • $ReadColumn(i): read the ith column (0-based) as a ChunkedArray.

Active bindings

  • $num_rows: number of rows.

  • $num_columns: number of columns.

  • $num_row_groups: number of row groups.

Examples

Run this code
# NOT RUN {
f <- system.file("v0.7.1.parquet", package = "arrow")
pq <- ParquetFileReader$create(f)
pq$GetSchema()
if (codec_is_available("snappy")) {
  # This file has compressed data columns
  tab <- pq$ReadTable()
  tab$schema
}
# }

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