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Use Lucene search engine for new RavenDB databases and flag indexes still on Corax - #5833
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New databases are created with Indexing.Static/Auto.SearchEngineType=Lucene: Lucene indexes are smaller, use less memory and are faster for the index definitions ServiceControl uses. Existing databases keep the engine they currently have configured, so no full index rebuild is triggered on upgrade.
New databases use Lucene, existing databases keep their configured search engine. Operators of existing databases now get a WARN at startup listing the indexes still on Corax so they can plan the transition to Lucene.
Surfaces the same information as the startup warning in ServicePulse via a custom check on both the Primary (main + throughput database) and Audit instances, so operators see it without inspecting logs.
mauroservienti
approved these changes
Aug 31, 2026
ramonsmits
marked this pull request as ready for review
September 2, 2026 13:43
ramonsmits
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Sep 3, 2026
PR #5840 introduced InternalCustomCheckClassification and PR #5833 added the Error/Audit Database Search Engine custom checks. Both merged independently, so the new checks were never registered and the CustomCheckTests.VerifyCustomChecks approval tests fail on master with "MISSING FROM InternalCustomCheckClassification".
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Summary
Load testing showed that Lucene indexes are smaller, use less RAM and are faster than Corax for the index definitions ServiceControl uses. This PR moves new databases to Lucene while leaving existing databases untouched, and makes it visible to operators when their indexes are still on Corax.
Switching an existing database is deliberately not done automatically: changing the search engine triggers a full rebuild of all indexes, which on very large databases can take days depending on available compute and degrades ingestion/indexing rates while it runs. Migration remains an operator decision (docs guidance to follow).
Note
The default RavenDB full-text search engine changes from Corax to Lucene to resolve performance and stability issues on large database instances. Existing indexes are not automatically updated, as an index rebuild can take significant time and can severely impact compute and storage utilization while it runs. For more information, see the 6.19 to 6.20 upgrade guide.
Changes
Indexing.Static/Auto.SearchEngineType=Lucene(Primary main + throughput databases, Audit).UpdateDatabaseSettingsis unchanged, so existing databases keep whatever engine they currently have configured.StartupChecks.WarnIfIndexesUseCorax, shared by both persisters).Error Database Search Engine/Audit Database Search Enginesurfacing the same information in ServicePulse (hourly).