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Update replacingmergetree.md

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removes confusion
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Andrey Kadochnikov 2020-06-19 16:07:22 +03:00 committed by GitHub
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docs/en/engines/table-engines/mergetree-family/replacingmergetree.md
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@ -5,7 +5,7 @@ toc_title: ReplacingMergeTree
# ReplacingMergeTree {#replacingmergetree} # ReplacingMergeTree {#replacingmergetree}
The engine differs from [MergeTree](../../../engines/table-engines/mergetree-family/mergetree.md#table_engines-mergetree) in that it removes duplicate entries with the same primary key value (or more accurately, with the same [sorting key](../../../engines/table-engines/mergetree-family/mergetree.md) value). The engine differs from [MergeTree](../../../engines/table-engines/mergetree-family/mergetree.md#table_engines-mergetree) in that it removes duplicate entries with the same [sorting key](../../../engines/table-engines/mergetree-family/mergetree.md) value.
Data deduplication occurs only during a merge. Merging occurs in the background at an unknown time, so you can’t plan for it. Some of the data may remain unprocessed. Although you can run an unscheduled merge using the `OPTIMIZE` query, don’t count on using it, because the `OPTIMIZE` query will read and write a large amount of data. Data deduplication occurs only during a merge. Merging occurs in the background at an unknown time, so you can’t plan for it. Some of the data may remain unprocessed. Although you can run an unscheduled merge using the `OPTIMIZE` query, don’t count on using it, because the `OPTIMIZE` query will read and write a large amount of data.
@ -33,7 +33,7 @@ For a description of request parameters, see [request description](../../../sql-
- `ver` — column with version. Type `UInt*`, `Date` or `DateTime`. Optional parameter. - `ver` — column with version. Type `UInt*`, `Date` or `DateTime`. Optional parameter.
When merging, `ReplacingMergeTree` from all the rows with the same primary key leaves only one: When merging, `ReplacingMergeTree` from all the rows with the same sorting key leaves only one:
- Last in the selection, if `ver` not set. - Last in the selection, if `ver` not set.
- With the maximum version, if `ver` specified. - With the maximum version, if `ver` specified.