Materialise FK lists in ImportMetadataViewset to avoid mis-planned subqueries

[rtibbles]

Summary

• __in=<queryset> in ImportMetadataViewset._serialize gave postgres correlated subqueries it mis-planned on fresh test DBs.
• Hung the postgres CI job ~100 min on ~30% of runs.
• Likely surfaced now because import metadata was recently extended to recurse through courses to transfer the full metadata.
• Switch to materialised lists with the existing __uuidin lookup (inlines IDs as SQL literals).

References

• Postgres CI hang observed intermittently across multiple recent PRs.

• Investigation + fault-handler instrumentation temporarily on: PR Remove task-worker multiprocessing #14754 (now removed). Captured stack (CI run):

  kolibri/core/content/test/test_public_api.py Timeout (0:02:00)!
  Thread 0x... (most recent call first):
    File ".../django/db/backends/utils.py", line 84 in _execute
    File ".../kolibri/core/content/public_api.py", line 134 in _serialize
    File ".../kolibri/core/content/public_api.py", line 180 in retrieve
    ...
    File ".../test_public_api.py", line 70 in test_import_metadata_assessmentmetadata
  

  Same stack across 11 consecutive 120-s dumps over ~2 h before the suite recovered.

Reviewer guidance

• test_public_api.py exercises every _serialize query against postgres — that suite plus the existing channel-import flow is the primary check.
• Empty-input cases for the __uuidin filters (e.g. a tag-less channel) flow through the EmptyResultSet branch — worth a glance at the loop's try/except.
• Lang-code dedupe replaces the prior Q(...) | Q(...) OR-subquery — confirm None is filtered and no codes are lost.

AI usage

Used Claude Code for investigation, diagnosis (fault-handler instrumentation + CI stack capture), and drafting the patch. I guided the lookup choice (__uuidin), reviewed the diff and drove revisions, and confirmed test_public_api.py passes against postgres locally.

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.19.5.dev0_git.20260528175452.pex
Windows Installer (EXE)	kolibri-0.19.5.dev0+git.20260528175452-windows-setup-unsigned.exe
Debian Package	kolibri_0.19.5.dev0+git.20260528175452-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.19.5.dev0+git.20260528175452.dmg
Android Package (APK)	kolibri-0.19.5.dev0+git.20260528175452-0.1.10-debug.apk
Raspberry Pi Image	kolibri-pi-image-0.19.5.dev0+git.20260528175452.zip
TAR file	kolibri-0.19.5.dev0+git.20260528175452.tar.gz
WHL file	kolibri-0.19.5.dev0+git.20260528175452-py2.py3-none-any.whl

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