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clarify which engines support final

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DanRoscigno 2022-12-21 09:07:40 -05:00
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docs/en/sql-reference/statements/select/from.md
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@ -21,8 +21,7 @@ Subquery is another `SELECT` query that may be specified in parenthesis inside `
When `FINAL` is specified, ClickHouse fully merges the data before returning the result and thus performs all data transformations that happen during merges for the given table engine.
It is applicable when selecting data from tables that use the [Replicated](../../../engines/table-engines/mergetree-family/replication.md) versions of `MergeTree` engines.
- [View](../../../engines/table-engines/special/view.md), [Buffer](../../../engines/table-engines/special/buffer.md), [Distributed](../../../engines/table-engines/special/distributed.md), and [MaterializedView](../../../engines/table-engines/special/materializedview.md) engines that operate over other engines, provided they were created over `MergeTree`-engine tables.
It is applicable when selecting data from ReplacingMergeTree, SummingMergeTree, AggregatingMergeTree, CollapsingMergeTree and VersionedCollapsingMergeTree tables.
Now `SELECT` queries with `FINAL` are executed in parallel and slightly faster. But there are drawbacks (see below). The [max_final_threads](../../../operations/settings/settings.md#max-final-threads) setting limits the number of threads used.