The timeseries bucket reopening pipeline relies on this statement to exclude buckets that are already full (and therefore should not be reopened). However, this field is not present/readable when the bucket is compressed, which they all are after the enabling of featureFlagTimeseriesAlwaysUseCompressedBuckets. This can lead to a bucket being selected for reopening that we have no chance of inserting a new document into rather than selecting an actually viable candidate.

One solution proposed over slack was to check the control.count field for the compressed case, but there were concerns that this could lead to matching many documents and having to scan through them which could impact performance.