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 ParquetReaderProperties
mmap Logical: whether to memory-map the file (default TRUE)
... Additional arguments, currently ignored
$ReadTable(col_select): get an arrow::Table from the file, possibly
with columns filtered by a character vector of column names or a
tidyselect specification.
$GetSchema(): get the arrow::Schema of the data in the file
# NOT RUN {
f <- system.file("v0.7.1.parquet", package="arrow")
pq <- ParquetFileReader$create(f)
pq$GetSchema()
if (codec_is_available("snappy")) {
# This file has compressed data columns
tab <- pq$ReadTable(starts_with("c"))
tab$schema
}
# }
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