This topic provides answers to some frequently asked questions about MaxCompute.
The following are frequently asked questions about MaxCompute:
What professional skills are required to use MaxCompute?
MaxCompute supports various data tunnels of computing models to meet your business requirements in different scenarios. To use MaxCompute for data analysis, you need only to be capable of using programming languages, such as SQL, Python, and Java.
Does MaxCompute provide an effective method to monitor business data?
MaxCompute lets you configure data monitoring rules only using the Data Quality feature of DataWorks. MaxCompute cannot monitor the changes in the fields of external data sources.
What is the role of a MaxCompute project?
A project is a basic organizational unit of MaxCompute. Similar to a database or schema in a traditional database system, a project is used to isolate users and control access requests. A project contains multiple objects, such as tables, resources, functions, and instances. You can have permissions to manage multiple projects. You can access objects of another project from your project after security authorization.
How do I obtain an AccessKey pair in MaxCompute?
You can go to the AccessKey Pair page to create or query an AccessKey pair.
If the AccessKey pair of the current account is disabled and a new AccessKey pair is created, are the auto triggered nodes that are created using the previous AccessKey pair affected?
Yes, the auto triggered nodes that are created using the previous AccessKey pair are affected. If you disable or delete an AccessKey pair, nodes in your DataWorks workspace fail to be run. Proceed with caution.
Does MaxCompute automatically compress data when I create a MaxCompute table? Can I specify the compression format and storage format?
MaxCompute automatically compresses data with an approximate compression ratio of 6.5:1. The default storage format is AliORC. You cannot customize the storage format or specify columns for compression.
Which types of tables are supported by MaxCompute?
MaxCompute supports two types of tables: internal tables and foreign tables. Support for foreign tables was introduced in MaxCompute V2.0.
For an internal table, all data is stored in MaxCompute. The columns in an internal table can be of any data type that MaxCompute supports.
For a foreign table, MaxCompute stores only the table's metadata, not the actual data. The data is stored in other services, such as OSS or Tablestore (OTS). You can use foreign tables to process unstructured data, such as video, audio, and genetic, meteorological, or geographic information, that is stored in OSS or OTS.
To accomplish tasks using user-defined functions (UDFs) or MapReduce, what resources do I need to use?
UDF: After you write a UDF, you must compile it into a JAR package and upload the package to MaxCompute as a resource. When you run the UDF, MaxCompute automatically downloads the resource package and executes your code.
MapReduce: After you write a MapReduce program, you must compile it into a JAR package and upload the package to MaxCompute as a resource. When you run a MapReduce job, the framework automatically downloads the resource package and executes your code.
You can upload text files and MaxCompute tables to MaxCompute as different types of resources. Then, you can read or use these resources when you run UDFs or MapReduce programs.
How do I understand common error messages in MaxCompute and troubleshoot issues based on the messages?
Common MaxCompute error messages use the following standard format: Error code: General description - Context-related description. The error messages differ for SQL, MapReduce, and tunnel jobs. For more information, see Error code overview.