See these pages for more details about Parquet Tools:
https://github.com/apache/parquet-mr/tree/master/parquet-tools
https://mvnrepository.com/artifact/org.apache.parquet/parquet-tools

Parquet is a columnar (column-oriented) storage format for Hadoop.

Columnar Layout	r{1}-c{1} , r{2}-c{1} , r{3}-c{1} , ...	r{1}-c{2} , r{2}-c{2} , r{3}-c{2} , ...	r{1}-c{3} , r{2}-c{3} , r{3}-c{3} , ...

Row-based Layout	r{1}-c{1} , r{1}-c{2} , r{1}-c{3} , ...	r{2}-c{1} , r{2}-c{2} , r{2}-c{3} , ...	r{3}-c{1} , r{3}-c{2} , r{3}-c{3} , ...

Key concepts
- Block Size
- Row Group
- Page

File:
- Magic Number
- Row group 0
 - Column 1
   - Page 0

- Usage (hadoop): hadoop jar parquet-tools-*.jar COMMAND [GENERIC-OPTIONS] [COMMAND-OPTIONS] PARUQET-FILE-PATH

- Usage (local): java -jar parquet-tools-*.jar COMMAND [GENERIC-OPTIONS] [COMMAND-OPTIONS] PARUQET-FILE-PATH

Commands:

   cat  Prints out content for a given parquet file.
  head  Prints out the first n records for a given parquet file (default: 5).
schema  Prints out the schema for a given parquet file.
  meta  Prints out metadata for a given parquet file.
  dump  Prints out row groups and metadata for a given parquet file.
 merge  Merges multiple Parquet files into one Parquet file.

Generic options:

--debug     |  Enable debug output.
-h,--help   |  Show this help string.
--no-color  |  Disable color output even if supported.

parquet-tools-*.jar print help when invoked without parameters or with "-help" or "--h" parameter:
hadoop jar parquet-tools-*.jar --help.

To print the help of a specific command use the following syntax:
hadoop jar parquet-tools-*.jar COMMAND --help.

Prints out content for a given parquet file.

• Usage:
  

  $ hadoop jar parquet-tools-1.9.0.jar cat --help
  usage: cat [GENERIC-OPTIONS] [COMMAND-OPTIONS] <input>
  
  where <input> is the parquet file to print to standard output.

  
  Command options:
  

  -j,--json  |  Show records in JSON format.

  
  
• Example:
  

  $ hadoop jar parquet-tools-1.9.0.jar cat hdfs://localhost:8020/test1.parquet
  INFO hadoop.ParquetFileReader: Initiating action with parallelism: 5
  INFO hadoop.ParquetFileReader: reading another 1 footers
  INFO hadoop.ParquetFileReader: Initiating action with parallelism: 5
  INFO hadoop.InternalParquetRecordReader: RecordReader initialized will read a total of 1 records.
  INFO hadoop.InternalParquetRecordReader: at row 0. reading next block
  INFO compress.CodecPool: Got brand-new decompressor [.snappy]
  INFO hadoop.InternalParquetRecordReader: block read in memory in 24 ms. row count = 1
  field1 = 123
  field2 = abc

Prints out the first n records for a given parquet file (default: 5).

• Usage:
  

  $ hadoop jar parquet-tools-1.9.0.jar head --help
  usage: head [GENERIC-OPTIONS] [COMMAND-OPTIONS] <input>
  
  where <input> is the parquet file to print to standard output.

  
  Command options:
  

  -n,--records <arg>  |  The number of records to show (default: 5).

  
  
• Example:
  

  $ hadoop jar parquet-tools-1.9.0.jar head hdfs://localhost:8020/test1.parquet
  INFO hadoop.ParquetFileReader: Initiating action with parallelism: 5
  INFO hadoop.ParquetFileReader: reading another 1 footers
  INFO hadoop.ParquetFileReader: Initiating action with parallelism: 5
  INFO hadoop.InternalParquetRecordReader: RecordReader initialized will read a total of 1 records.
  INFO hadoop.InternalParquetRecordReader: at row 0. reading next block
  INFO compress.CodecPool: Got brand-new decompressor [.snappy]
  INFO hadoop.InternalParquetRecordReader: block read in memory in 45 ms. row count = 1
  field1 = 123
  field2 = abc

  
  

  $ hadoop jar parquet-tools-1.9.0.jar head -n 10 hdfs://localhost:8020/test1.parquet

Prints out the schema for a given parquet file.

• Usage:
  

  $ hadoop jar parquet-tools-1.9.0.jar schema --help
  usage: schema [GENERIC-OPTIONS] [COMMAND-OPTIONS] <input>
  
  where <input> is the parquet file containing the schema to show.

  
  Command options:
  

  -d,--detailed  |  Show detailed information about the schema.

  
  
• Example:
  

  $ hadoop jar parquet-tools-1.9.0.jar schema hdfs://localhost:8020/test1.parquet
  message spark_schema {
    optional int64 field1;
    optional binary field2 (UTF8);
  }

Prints out metadata for a given parquet file.

• Usage:
  

  $ hadoop jar parquet-tools-1.9.0.jar meta --help
  usage: meta [GENERIC-OPTIONS] [COMMAND-OPTIONS] <input>
  
  where <input> is the parquet file to print to standard output.

  
  
• Example:
  

  $ hadoop jar parquet-tools-1.9.0.jar meta hdfs://localhost:8020/test1.parquet
  INFO hadoop.ParquetFileReader: Initiating action with parallelism: 5
  INFO hadoop.ParquetFileReader: reading another 1 footers
  INFO hadoop.ParquetFileReader: Initiating action with parallelism: 5
  file:          hdfs://localhost:8020/test1.parquet
  creator:       parquet-mr version 1.8.3 (build aef7230e114214b7cc962a8f3fc5aeed6ce80828)
  extra:         org.apache.spark.sql.parquet.row.metadata = {"type":"struct","fields":[{"name":"field1","type":"long","nullable":true,"metadata":{}},{"name":"field2","type":"string","nullable":true,"metadata":{}}]}
  
  file schema:   spark_schema
  --------------------------------------------------------------------------------
  field1:       OPTIONAL INT64 R:0 D:1
  field2:       OPTIONAL BINARY O:UTF8 R:0 D:1
  
  row group 1:   RC:2 TS:925 OFFSET:1
  --------------------------------------------------------------------------------
  field1:        INT64 SNAPPY DO:0 FPO:4 SZ:87/87/1.00 VC:5 ENC:BIT_PACKED,RLE,PLAIN
  field2:        BINARY SNAPPY DO:0 FPO:180 SZ:315/319/1.01 VC:5 ENC:BIT_PACKED,RLE,PLAIN

Prints out row groups and metadata for a given parquet file.

• Usage:
  

  $ hadoop jar parquet-tools-1.9.0.jar dump --help
  usage: dump [GENERIC-OPTIONS] [COMMAND-OPTIONS] <input>
  
  where <input> is the parquet file to print to standard output.

  
  Command options:
  

  -c,--column <arg>  |  Dump only the given column, can be specified more than once.
  -d,--disable-data  |  Do not dump column data.
  -m,--disable-meta  |  Do not dump row group and page metadata.
  -n,--disable-crop  |  Do not crop the output based on console width.

  
  
• Example:
  

  $ hadoop jar parquet-tools-1.9.0.jar dump hdfs://localhost:8020/test1.parquet
  INFO compress.CodecPool: Got brand-new decompressor [.snappy]
  row group 0
  --------------------------------------------------------------------------------
  field1:        INT64 SNAPPY DO:0 FPO:4 SZ:87/87/1.00 VC:5 ENC:RLE,BIT [more]...
  field2:        BINARY SNAPPY DO:0 FPO:180 SZ:315/319/1.01 VC:5 ENC:RL [more]...
  
      field1 TV=1 RL=0 DL=1
      ----------------------------------------------------------------------------
      page 0:                           DLE:RLE RLE:BIT_PACKED VLE:PLAIN [more]... VC:5
  
      field2 TV=1 RL=0 DL=1
      ----------------------------------------------------------------------------
      page 0:                           DLE:RLE RLE:BIT_PACKED VLE:PLAIN [more]... VC:5
  
  INT64 field1
  --------------------------------------------------------------------------------
  *** row group 1 of 1, values 1 to 1 ***
  value 1: R:0 D:1 V:1173960334
  
  BINARY field2
  --------------------------------------------------------------------------------
  *** row group 1 of 1, values 1 to 1 ***
  value 1: R:0 D:1 V:0-c281a405-1dc6-3a60-90c1-790de339df40

Merges multiple Parquet files into one Parquet file.

• Usage:
  

  $ hadoop jar parquet-tools-1.9.0.jar merge --help
  usage: merge [GENERIC-OPTIONS] [COMMAND-OPTIONS] <input> [<input> ...] <output>
  
  where:
  <input> is the source parquet files/directory to be merged.
  <output> is the destination parquet file.

  
  
• Example:
  

  $ hadoop jar parquet-tools-1.9.0.jar merge hdfs://localhost:8020/test1.parquet hdfs://localhost:8020/test2.parquet hdfs://localhost:8020/test1-test2.parquet