How do I get schema / column names from parquet fi

问题:

I have a file stored in HDFS as part-m-00000.gz.parquet

I've tried to run hdfs dfs -text dir/part-m-00000.gz.parquet but it's compressed, so I ran gunzip part-m-00000.gz.parquet but it doesn't uncompress the file since it doesn't recognise the .parquet extension.

How do I get the schema / column names for this file?

回答1:

You won't be able "open" the file using a hdfs dfs -text because its not a text file. Parquet files are written to disk very differently compared to text files.

And for the same matter, the Parquet project provides parquet-tools to do tasks like which you are trying to do. Open and see the schema, data, metadata etc.

Check out the parquet-tool project (which is put simply, a jar file.) parquet-tools

Also Cloudera which support and contributes heavily to Parquet, also has a nice page with examples on usage of parquet-tools. A example from that page for your use case is

parquet-tools schema part-m-00000.parquet

Checkout the Cloudera page. Using the Parquet File Format with Impala, Hive, Pig, HBase, and MapReduce

回答2:

If your Parquet files are located in HDFS or S3 like me, you can try something like the following:

HDFS

parquet-tools schema hdfs://<YOUR_NAME_NODE_IP>:8020/<YOUR_FILE_PATH>/<YOUR_FILE>.parquet

S3

parquet-tools schema s3://<YOUR_BUCKET_PATH>/<YOUR_FILE>.parquet

Hope it helps.

回答3:

Maybe it's capable to use a desktop application to view Parquet and also other binary format data like ORC and AVRO. It's pure Java application so that can be run at Linux, Mac and also Windows. Please check Bigdata File Viewer for details.

It supports complex data type like array, map, etc.

Just one reminder, it doesn't enable HDFS interface yet. Users can only load files from local filesystem.

回答4:

Since it is not a text file, you cannot do a "-text" on it. You can read it easily through Hive even if you do not have the parquet-tools installed, if you can load that file to a Hive table.