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Update clickhouse-v21.12-released.md

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website/blog/en/2021/clickhouse-v21.12-released.md
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@ -228,10 +228,10 @@ The query can be automatically rewritten to:
SELECT count() FROM hits WHERE Domain = 'ghe.clickhouse.tech'
```
because `Domain` column is smaller, more compressable, will be faster to read and it does not require calculation of domain.
because `Domain` column is smaller, more compressable, will be faster to read and it does not require calculation of the domain from URL.
The only thing you need is to enable the `optimize_using_constraints` and `optimize_substitute_columns` settings.
As a bonus, new type of constraints are introduced: `ASSUME`.
As a bonus, new type of constraints is introduced: `ASSUME`.
```
CONSTRAINT my_constraint ASSUME Domain = domainWithoutWWW(URL)