Details
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Improvement
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Status: Triage Needed
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Normal
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Resolution: Unresolved
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None
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All
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Description
SAI supports row-awareness in that it indexes both the partition key and the clustering key of a row. This improves query performance significantly for wide partitions with many rows but it can impact performance for small partitions where it could make sense to bypass row-awareness post-filter the results (read the whole partition) or batch rows for a single partition.
However this is achieved it would be necessary for the index to have an idea of the size of the partition being read and to be aware of whether reading the whole partition is likely to improve read performance.
SAI is aware of partition sizes during indexing so one option would be feed these sizes into a histogram in the index metadata and apply a set of rules to this metadata to decide whether we should attempt any optimisation.