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  1. Core Server
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cache pressure causes one bucket per single document with time series collections

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      In a sharded mongodb cluster (in my case 7.0.4).
      Insert time-series collection into a sharded database. Either keep inserting, or in my case, delete the one, and re-insert the same time-series collection.
      The bucket count equals the document count.

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      In a sharded mongodb cluster (in my case 7.0.4). Insert time-series collection into a sharded database. Either keep inserting, or in my case, delete the one, and re-insert the same time-series collection. The bucket count equals the document count.
    • Execution Team 2024-04-29, Execution Team 2024-05-13

      A while (several days usually) after starting up the database (sharded cluster), newly inserted time series collection will have exactly (as far as I personally observed) as many buckets as documents, regardless of granularity or metafield settings. The stats() command shows that the buckets were closed due to cache pressure (numBucketsClosedDueToCachePressure).

      I also experience the issue with after deleting a time series collection, and inserting either the same or other collections.

      This behavior has also been documented/observed in:
      https://www.mongodb.com/community/forums/t/suboptimal-bucket-creation-in-timeseries-collection-due-to-cache-pressure/249863
      https://dba.stackexchange.com/questions/336013/mongodb-timeseries-data-at-high-load-causes-cache-pressure-in-time
      https://www.mongodb.com/community/forums/t/why-timeseries-bucket-count-is-different-on-2-independent-environment-with-same-data/265066/

            Assignee:
            daotang.yang@mongodb.com Daotang Yang
            Reporter:
            zongli@amzracing.ch Zongji Li
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              Created:
              Updated: