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@ -993,11 +993,11 @@ They can be used for prewhere optimization only if we enable `set allow_statisti
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- `TDigest`
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Stores distribution of values from numeric columns in [TDigest](https://github.com/tdunning/t-digest) sketch.
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[TDigest](https://github.com/tdunning/t-digest) sketches which allow to compute approximate percentiles (e.g. the 90th percentile) for numeric columns.
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- `Uniq`
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Estimate the number of distinct values of a column by HyperLogLog.
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[HyperLogLog](https://en.wikipedia.org/wiki/HyperLogLog) sketches which provide an estimation how many distinct values a column contains.
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## Column-level Settings {#column-level-settings}
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@ -28,6 +28,6 @@ There is an example adding two statistics types to two columns:
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ALTER TABLE t1 MODIFY STATISTICS c, d TYPE TDigest, Uniq;
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```
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:::note
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:::note
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Statistic manipulation is supported only for tables with [`*MergeTree`](../../../engines/table-engines/mergetree-family/mergetree.md) engine (including [replicated](../../../engines/table-engines/mergetree-family/replication.md) variants).
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:::
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