Reading parquet files from multiple directories in Pyspark

问题

I need to read parquet files from multiple paths that are not parent or child directories.

for example,

dir1 ---
       |
       ------- dir1_1
       |
       ------- dir1_2
dir2 ---
       |
       ------- dir2_1
       |
       ------- dir2_2

sqlContext.read.parquet(dir1) reads parquet files from dir1_1 and dir1_2

Right now I'm reading each dir and merging dataframes using "unionAll". Is there a way to read parquet files from dir1_2 and dir2_1 without using unionAll or is there any fancy way using unionAll

Thanks

回答1:

A little late but I found this while I was searching and it may help someone else...

You might also try unpacking the argument list to spark.read.parquet()

paths=['foo','bar']
df=spark.read.parquet(*paths)

This is convenient if you want to pass a few blobs into the path argument:

basePath='s3://bucket/'
paths=['s3://bucket/partition_value1=*/partition_value2=2017-04-*',
       's3://bucket/partition_value1=*/partition_value2=2017-05-*'
      ]
df=spark.read.option("basePath",basePath).parquet(*paths)

This is cool cause you don't need to list all the files in the basePath, and you still get partition inference.

回答2:

Both the parquetFile method of SQLContext and the parquet method of DataFrameReader take multiple paths. So either of these works:

df = sqlContext.parquetFile('/dir1/dir1_2', '/dir2/dir2_1')

df = sqlContext.read.parquet('/dir1/dir1_2', '/dir2/dir2_1')

回答3:

Just taking John Conley's answer, and embellishing it a bit and providing the full code (used in Jupyter PySpark) as I found his answer extremely useful.

from hdfs import InsecureClient
client = InsecureClient('http://localhost:50070')

import posixpath as psp
fpaths = [
  psp.join("hdfs://localhost:9000" + dpath, fname)
  for dpath, _, fnames in client.walk('/eta/myHdfsPath')
  for fname in fnames
]
# At this point fpaths contains all hdfs files 

parquetFile = sqlContext.read.parquet(*fpaths)


import pandas
pdf = parquetFile.toPandas()
# display the contents nicely formatted.
pdf

来源：https://stackoverflow.com/questions/37257111/reading-parquet-files-from-multiple-directories-in-pyspark

标签

pyspark

parquet