How to use the command parquet-tools (with examples)
Parquet-tools is a command-line tool that allows users to show, inspect, and manipulate Parquet files. It provides various functionality to work with Parquet files such as displaying the content, printing the schema and metadata, merging files, and more. This article will illustrate each of these use cases with examples.
Use case 1: Display the content of a Parquet file
Code:
parquet-tools cat path/to/parquet
Motivation: This use case is helpful when you need to view the entire content of a Parquet file.
Explanation: The command parquet-tools cat is used to display the content of a Parquet file. The argument path/to/parquet specifies the path to the Parquet file.
Example output:
{ "name": "John", "age": 25 }
{ "name": "Mary", "age": 30 }
{ "name": "Sam", "age": 35 }
Use case 2: Display the first few lines of a Parquet file
Code:
parquet-tools head path/to/parquet
Motivation: When working with large Parquet files, it can be useful to quickly inspect the first few lines to get an overview of the data.
Explanation: The command parquet-tools head is used to display the first few lines of a Parquet file. The argument path/to/parquet specifies the path to the Parquet file.
Example output:
{ "name": "John", "age": 25 }
{ "name": "Mary", "age": 30 }
{ "name": "Sam", "age": 35 }
Use case 3: Print the schema of a Parquet file
Code:
parquet-tools schema path/to/parquet
Motivation: Understanding the schema of a Parquet file is essential for working with the data effectively. This use case allows you to retrieve the schema information.
Explanation: The command parquet-tools schema is used to print the schema of a Parquet file. The argument path/to/parquet specifies the path to the Parquet file.
Example output:
message example_schema {
required binary name (UTF8);
required int32 age;
}
Use case 4: Print the metadata of a Parquet file
Code:
parquet-tools meta path/to/parquet
Motivation: The metadata of a Parquet file includes valuable information such as file version, created by, and more. This use case allows you to retrieve the metadata.
Explanation: The command parquet-tools meta is used to print the metadata of a Parquet file. The argument path/to/parquet specifies the path to the Parquet file.
Example output:
creator: parquet-mr version 1.10.0
file schema: example_schema
...
Use case 5: Print the content and metadata of a Parquet file
Code:
parquet-tools dump path/to/parquet
Motivation: This use case combines the display of both the content and metadata of a Parquet file, providing a comprehensive view of the data.
Explanation: The command parquet-tools dump is used to print the content and metadata of a Parquet file. The argument path/to/parquet specifies the path to the Parquet file.
Example output:
creator: parquet-mr version 1.10.0
file schema: example_schema
{ "name": "John", "age": 25 }
{ "name": "Mary", "age": 30 }
{ "name": "Sam", "age": 35 }
Use case 6: Concatenate several Parquet files into the target one
Code:
parquet-tools merge path/to/parquet1 path/to/parquet2 path/to/target_parquet
Motivation: When you have multiple Parquet files containing related data, merging them into a single file can be convenient for further analysis or processing.
Explanation: The command parquet-tools merge is used to concatenate several Parquet files into the target file specified by path/to/target_parquet. The arguments path/to/parquet1 and path/to/parquet2 represent the paths to the Parquet files to be merged.
Example output: No output will be displayed if the merge is successful.
Use case 7: Print the count of rows in a Parquet file
Code:
parquet-tools rowcount path/to/parquet
Motivation: Sometimes you need to determine the number of rows in a Parquet file, especially when dealing with large datasets.
Explanation: The command parquet-tools rowcount is used to print the count of rows in a Parquet file. The argument path/to/parquet specifies the path to the Parquet file.
Example output:
Row count: 1000
Use case 8: Print the column and offset indexes of a Parquet file
Code:
parquet-tools column-index path/to/parquet
Motivation: Understanding the column and offset indexes of a Parquet file can be useful for querying specific data efficiently.
Explanation: The command parquet-tools column-index is used to print the column and offset indexes of a Parquet file. The argument path/to/parquet specifies the path to the Parquet file.
Example output:
Column indexes:
name: 0
age: 1
Offset indexes:
row_group: 0
column: 0
offset: 100
Conclusion:
Parquet-tools is a versatile command-line tool for working with Parquet files. It provides various commands to display content, print schema and metadata, merge files, and more. By using the examples provided in this article, users can easily perform common tasks related to Parquet file manipulation.
