Add support for filter expression in GroupConcat #948
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GroupConcat did not support fitler expression. This PR adds support based on Django `Count` aggregate. https://github.com/adamchainz/django-mysql/blob/main/src/django_mysql/models/aggregates.py
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Nice work starting on this.
The tests are failing because the package requires test coverage - please add tests in the existing tests for group concat. It looks like we'll need at least two, depending on the value of distinct.
Also please update the documentation the changelog.
| if self.filter: | ||
| extra_context["distinct"] = "DISTINCT " if self.distinct else "" | ||
| copy = self.copy() | ||
| copy.filter = None | ||
| source_expressions = copy.get_source_expressions() | ||
| condition = When(self.filter, then=source_expressions[0]) | ||
| copy.set_source_expressions([Case(condition)] + source_expressions[1:]) | ||
| return super(Aggregate, copy).as_sql(compiler, connection, **extra_context) |
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I haven't looked into it, but it's a bit odd that you're skipping the existing implementation and calling super(). The implemetnation below covers the SQL oddities in GROUP_CONCAT, I think we'd still want to use it, just tweak adding the filter there.
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I'm not sure we need keep the existing pathway in the long term. It's probably better to let Aggregate.as_sql() perform the work based on the template.
If you look at the code for Count, you'll see there are 2 paths, one when filter is set, the other when it's not. I think we should have a similar structure here, but avoid manual handcrafting as much as possible because this is likely fragile.
Co-authored-by: Adam Johnson <[email protected]>
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I missed this in the first commit
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I've updated the history file. I'm not sure if this is the file you had in mind. |
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THat's the file, but you've done so in a separate PR: #949. Please do so in this PR, on the same branch. |
due to the introduction of an auxiliary function.
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Still waiting on docs, changelog note, and tests. |
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@caramdache Any status updates? Wondering if I can help implement this somehow without having to start a whole new MR. |
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I think it's unlikely they'll return, please start a new PR. You can pull their changes with |
Fixes #947.
GroupConcat did not support fitler expression. This PR adds support based on Django
Countaggregate.https://github.com/adamchainz/django-mysql/blob/main/src/django_mysql/models/aggregates.py