Reduce data export memory usage

[tudddorrr]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 93.75000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.78%. Comparing base (24eab9c) to head (b0bccbc).
⚠️ Report is 3 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/lib/queues/data-exports/dataExportProcessor.ts	93.75%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #928      +/-   ##
===========================================
+ Coverage    97.63%   97.78%   +0.14%     
===========================================
  Files          406      406              
  Lines         6649     6634      -15     
  Branches       884      884              
===========================================
- Hits          6492     6487       -5     
+ Misses          73       64       -9     
+ Partials        84       83       -1     

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[claude]

PR Review: Reduce data export memory usage

This is a clean and well-motivated refactor. The core approach — pre-fetching prop keys with targeted queries and streaming entities in a single pass — is the right fix for memory-bound exports. The alias cache eviction is correctly placed after all events on a page have been yielded, the em.fork() per entity type prevents identity map cross-contamination, and the new tests cover both the new leaderboard-prop path and the re-fetch-after-eviction path.

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1. Code quality and best practices

Minor — streamCSVToArchive silently depends on propKeys arriving pre-sorted

The function builds metaPropKeys / otherPropKeys by filtering without re-sorting:

const metaPropKeys = propKeys.filter((k) => k.startsWith('META_'))
const otherPropKeys = propKeys.filter((k) => !k.startsWith('META_'))

This produces deterministic column order only because all three callers use ORDER BY ... ASC in their queries. The parameter is declared as propKeys: string[] = [] with no indication of this expectation. A future caller passing an unsorted array would produce non-deterministic (but silently correct-looking) CSV headers. A doc comment on the parameter would make this contract explicit.

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2. Potential bugs or issues

No issues found.

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3. Performance considerations

No issues found.

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4. Security concerns

No issues found.

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5. Test coverage

Minor — Cache-eviction test accesses private method via prototype with unexpected this binding

const proto = Object.getPrototypeOf(exporter)
for await (const event of proto.streamEvents(dataExport, em, true)) {

Calling proto.streamEvents(...) sets this to DataExporter.prototype rather than the exporter instance. It works today because streamEvents never references this, but it is subtly fragile. The conventional alternative for accessing a private method in tests is a cast:

for await (const event of (exporter as any).streamEvents(dataExport, em, true)) {

This preserves the correct this binding and remains safe if streamEvents ever calls an instance method internally.

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Overall this is a solid improvement — no blockers, just two minor nits worth noting before merge.