Side bucket catalog for time series updates and deletes
Parent: Bucket catalog memory and closure reasons · Published reference · snapshot 2026-10-24 · skill mongodb-cohort-bd6489c69c3d
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Source-anchored research for Side bucket catalog for time series updates and deletes. Run status: COMPLETED.
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How it works
- When the stage is destroyed and has newly inserted bucket IDs, it finishes their direct-write tracking in the global catalog and merges the side catalog collection execution statistics into that catalog. Consequently, those statistics are not necessarily a separate reporting namespace. (low confidence) (verified as of 2026-10-24) [source]
Problems, failure modes and limitations
- For multi updates, the implementation guide describes spooling scanned bucket record IDs and inserting updated measurements into new buckets to avoid the Halloween problem; the spool can spill when its memory limit is reached. (low confidence) (verified as of 2026-10-24) [source]
Facts and statements
- In the inspected master implementation, TimeseriesModifyStage allocates a side BucketCatalog only for updates, with one stripe and getTimeseriesSideBucketCatalogMemoryUsageThresholdBytes as its threshold callback. (medium confidence) (verified as of 2026-10-24) [source]
- Measurement updates remove old values and insert changed measurements into new buckets; unchanged measurements remain in the original bucket, which is deleted if none remain. (high confidence) (verified as of 2026-10-24) [source]
- timeseriesSideBucketCatalogMemoryUsageThreshold controls idle-bucket expiry in the side catalog. The inspected MongoDB parameter definition and ApsaraDB 8.0 table specify a default of 104857600 bytes; the MongoDB definition permits startup and runtime changes. (high confidence) [source]
- Measurement deletes repack surviving measurements into the original bucket, or delete that bucket if none survive. A predicate covering a whole bucket can bypass unpacking. The delete helper receives no side catalog. (high confidence) (verified as of 2026-10-24) [source]
- ApsaraDB’s kernel-parameter release notes list the side-catalog memory threshold for MongoDB 8.0 in the July 2025 additions. This dates the managed-service exposure, not the upstream feature’s introduction. (low confidence) (verified as of 2026-06-22) [source]
- timeseriesSideBucketCatalogMemoryUsageThreshold defaults to 104857600 bytes (100 MiB). Upstream IDL and Alibaba MongoDB 8.0 documentation describe it as the memory threshold above which idle side-catalog buckets expire; they do not describe a strict total-memory ceiling. (medium confidence) (verified as of 2026-10-24) [source]
- Upstream IDL allows the side-catalog threshold to be set at startup or runtime. Alibaba lists its managed MongoDB 8.0 parameter with a 52428800–209715200-byte range and no restart requirement. That service range must not be assumed to be an upstream validator. (medium confidence) (verified as of 2026-10-24) [source]
Children
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