问题
I'm using parquet-tools to merge parquet files. But it seems that parquet-tools needs an amount of memory as big as the merged file. Do we have other ways or configurable options in parquet-tools to use memory more effectively? Cause I run the merge job in as a map job on hadoop env. And the container gets killed every time cause it used more memory than it is provided.
Thank you.
回答1:
I wouldn't recommend using parquet-tools merge, since it just places row groups one after the another, so you will still have small groups, just packed together in a single file. The resulting file will typically not have noticably better performance, and under certain circumstances it may even perform worse than separate files. See PARQUET-1115 for details.
Currently the only proper way to merge Parquet files is to read all data from them and write it to a new Parquet file. You can do it with a MapReduce job (requires writing custom code for this purpose) or using Spark, Hive or Impala.
来源：https://stackoverflow.com/questions/50299815/effectively-merge-big-parquet-files