read a parquet files from HDFS using PyArrow

问题

I know I can connect to an HDFS cluster via pyarrow using pyarrow.hdfs.connect()

I also know I can read a parquet file using pyarrow.parquet's read_table()

However, read_table() accepts a filepath, whereas hdfs.connect() gives me a HadoopFileSystem instance.

Is it somehow possible to use just pyarrow (with libhdfs3 installed) to get a hold of a parquet file/folder residing in an HDFS cluster? What I wish to get to is the to_pydict() function, then I can pass the data along.

回答1:

Try

fs = pa.hdfs.connect(...)
fs.read_parquet('/path/to/hdfs-file', **other_options)

or

import pyarrow.parquet as pq
with fs.open(path) as f:
    pq.read_table(f, **read_options)

I opened https://issues.apache.org/jira/browse/ARROW-1848 about adding some more explicit documentation about this

回答2:

I tried the same via Pydoop library and engine = pyarrow and it worked perfect for me.Here is the generalized method.

!pip install pydoop pyarrow
import pydoop.hdfs as hd

#read files via Pydoop and return df

def readParquetFilesPydoop(path):
    with hd.open(path) as f:
        df = pd.read_parquet(f ,engine='pyarrow')
        logger.info ('file: ' +  path  +  ' : ' + str(df.shape))
        return df

来源：https://stackoverflow.com/questions/47443151/read-a-parquet-files-from-hdfs-using-pyarrow