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  1. Apache Drill
  2. DRILL-4130

Ability to set settings at Table or View level rather than SESSION or SYSTEM



    • Type: Improvement
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: 1.3.0
    • Fix Version/s: Future
    • Component/s: Metadata
    • Environment:



      There are a number of settings within drill for handling data that due to low level of granularity there may be unintended data reading consequences. A few examples include:


      (There are likely more, these are some I've worked with)

      The documentation on https://drill.apache.org/docs/json-data-model/ outlines how when dealing with certain types of data, that these settings can be helpful for reading, and indeed some queries fail with a suggestion to change these settings.

      A few points here. 1. The documentation suggests alter system commands. This is not ideal as it changes the default way drill handles data for all users AND not all users will (should) have the privs to enter this command. The documentation at a minimum should show alter session (or provide a clearer understanding of the difference)

      But even with alter session, that affects reads for all JSON files for that session, when in reality, the reasoning behind the setting is to be able to read a specific table that has poorly formed JSON. Thus, issuing a command that alters how Drill reads all JSON in order to read one table of JSON could have unintended consequences, especially for a user who just wants to be able to read things and issues commands without thinking things through.

      Now as an administrator, there are two use cases here. One is I have a table of poorly formed JSON that requires one of these settings, and I can't change the source, therefore, can I create a view that makes it so all reads of this table are done with the more permissive setting? Setting these in a view would be very helpful from an administrator perspective for known bad data sources. Keep users from having to think about it, and let them do their exploration.

      The other use case, is the ability for a user to set a session level read that only applies for the table being read. alter session set "%tablename%.store.json.read_numbers_as_double = true" (and have the errors that display use that as the default suggestion) that way, the user can issue the command, but not have downstream consequences in their session while reading other tables.

      Either case is valuable to an administrator, and could help prevent data read issues.


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              • Assignee:
                mandoskippy John Omernik
              • Votes:
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