[jira] [Created] (ASTERIXDB-2194) Introduce datasource functions

["Abdullah Alamoudi (JIRA)" <ji...@apache.org>]

Abdullah Alamoudi created ASTERIXDB-2194:
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             Summary: Introduce datasource functions
                 Key: ASTERIXDB-2194
                 URL: https://issues.apache.org/jira/browse/ASTERIXDB-2194
             Project: Apache AsterixDB
          Issue Type: Improvement
          Components: COMP - Compiler
            Reporter: Abdullah Alamoudi
            Assignee: Abdullah Alamoudi


Sometimes, we would like to be able to query system status. For example:
   1. Disk space.
   2. Number of components of a dataset.
   3. Memory usage.
And many others. Being able to query such information and utilize the power of the query language and the runtime makes a great investigative/diagnostic tool.

Currently, there is no easy way to do that. Such functionality can be achieved through:
1. External datasets but that takes a lot of work in terms of development and usage.
2. Use specific diagnostic end points but then that is also a lot of development work and you end up losing the ability to use the query language.

Current proposal is to introduce datasource functions. A datasource function is different from normal functions as:
1. Takes constants ( as opposed to variables).
2. Has location constraints "For a start, it can be on all nodes".

An example would be the function dataset_resources(String dataverse, String dataset);
This function takes a dataverse and a dataset and produce a set of json representing the disk resources of the dataset.






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