fix(lapis): do not cache aggregations with many group by fields - #1850
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Aggregations that group by more than 20 columns (plain fields plus sequence-position fields) are no longer cached. The cache materializes the full result into a List to store it; for high-cardinality group-bys this can exhaust the heap (and did, causing a LAPIS outage). Such queries are now streamed straight through instead. Their cache hit rate is close to zero anyway since each filter combination is unique. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01Q5mqrj8VN12QZfxqGNEb1d
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🟢 Approval recommended
The implementation matches the stated requirement and includes appropriate unit and client-level coverage.
Pull request overview
Prevents heap exhaustion by streaming aggregations grouped by more than 20 fields instead of caching them.
Changes:
- Adds a maximum cacheable group-by field count.
- Counts metadata and sequence-position fields together.
- Tests cacheability and uncached client behavior.
File summaries
| File | Description |
|---|---|
lapis/src/main/kotlin/org/genspectrum/lapis/silo/SiloQuery.kt |
Disables caching above the threshold. |
lapis/src/test/kotlin/org/genspectrum/lapis/silo/SiloQueryTest.kt |
Tests threshold behavior. |
lapis/src/test/kotlin/org/genspectrum/lapis/silo/SiloClientTest.kt |
Verifies large aggregations bypass caching. |
Review details
- Files reviewed: 3/3 changed files
- Comments generated: 0
- Review effort level: Balanced
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fengelniederhammer
approved these changes
Sep 3, 2026
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Looks reasonable 👍
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resolves #1849
Aggregations that group by more than 20 columns (plain fields plus sequence-position fields) are no longer cached. The cache materializes the full result into a List to store it; for high-cardinality group-bys this can exhaust the heap (and did, causing a LAPIS outage). Such queries are now streamed straight through instead. Their cache hit rate is close to zero anyway since each filter combination is unique.
PR Checklist
All necessary changes are explained in thellms.txt.