Add possibility to show random tasks

[rschwanhold]

Mailable description of changes:

• The admin has now the possibility to show the task in a random order. This feature is used when you click on 'Show random subset'. The behavior of 'Search' is still the same.

Steps to test:

• go to Administration >> Tasks
  • e.g. select Project
  • click 'Search': the result should stay the same every time you click on it
  • click 'Show random subset': the order of the result should change every time you click it (if you have at lest 2 Tasks that fits the criteria)

Issues:

• fixes Add possibility to randomize Task search result sample #2803

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• Ready for review

[jstriebel]

@rschwanhold : Please add the change notes to the changelog

[fm3]

Works for me (but I’m a bit scared of the performance on a 3M-entry-table – but I assume this is not used with a super high frequency anyway). Backend code looks okay to me.
@philippotto could you have a look at the js changes? Also, do you think it is confusing that the loading symbol still appears in the original Search button rather than the new Show random subset button? Here, too, I think it’s acceptable but I’d like to hear your opinion.

[philippotto]

Works for me (but I’m a bit scared of the performance on a 3M-entry-table – but I assume this is not used with a super high frequency anyway). Backend code looks okay to me.

We can test this directly after deployment. As long as the server doesn't freeze, everything should be fine. The functionality is probably not used very often.

@philippotto could you have a look at the js changes? Also, do you think it is confusing that the loading symbol still appears in the original Search button rather than the new Show random subset button? Here, too, I think it’s acceptable but I’d like to hear your opinion.

Yes, I tweaked the code a bit and combined the two search buttons (which also solves the "wrong" place for the loading indicator). Should be good to go now.

[rschwanhold]

@fm3 the performance optimized way would be to use the "tablesample" method from postgres. This works really well for big tables, but this does only work with tables or materialized views.

[fm3]

@rschwanhold ok, then let’s do it with order by random for now. If it’s super slow we can still optimize later :)