ParquetFileReader class
This class enables you to interact with Parquet files.
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
$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.
$num_rows: number of rows.
$num_columns: number of columns.
$num_row_groups: number of row groups.
## Not run:
f <- system.file("v0.7.1.parquet", package="arrow")
pq <- ParquetFileReader$create(f)
pq$GetSchema()
if (codec_is_available("snappy")) {
# This file has compressed data columns
tab <- pq$ReadTable()
tab$schema
}
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.