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Merge pull request #7483 from ClickHouse/filimonov-mutationsdocs-patch

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remove some obsolete notes about mutations
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alexey-milovidov 2019-10-28 16:15:14 +03:00 committed by GitHub
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docs/en/query_language/alter.md
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@ -294,7 +294,7 @@ This query creates a local backup of a specified partition. If the `PARTITION` c
Note that for old-styled tables you can specify the prefix of the partition name (for example, '2019') - then the query creates the backup for all the corresponding partitions. Read about setting the partition expression in a section [How to specify the partition expression](#alter-how-to-specify-part-expr).
!!! note
The entire backup process is performed without stopping the server.
The entire backup process is performed without stopping the server.
At the time of execution, for a data snapshot, the query creates hardlinks to a table data. Hardlinks are placed in the directory `/var/lib/clickhouse/shadow/N/...`, where:
@ -389,7 +389,7 @@ Possible values: `0` – do not wait; `1` – only wait for own execution (defau
Mutations are an ALTER query variant that allows changing or deleting rows in a table. In contrast to standard `UPDATE` and `DELETE` queries that are intended for point data changes, mutations are intended for heavy operations that change a lot of rows in a table.
The functionality is in beta stage and is available starting with the 1.1.54388 version. Currently `*MergeTree` table engines are supported (both replicated and unreplicated).
Currently `*MergeTree` table engines are supported (both replicated and unreplicated).
Existing tables are ready for mutations as-is (no conversion necessary), but after the first mutation is applied to a table, its metadata format becomes incompatible with previous server versions and falling back to a previous version becomes impossible.
@ -405,7 +405,7 @@ The `filter_expr` must be of type UInt8. The query deletes rows in the table for
ALTER TABLE [db.]table UPDATE column1 = expr1 [, ...] WHERE filter_expr
```
The command is available starting with the 18.12.14 version. The `filter_expr` must be of type UInt8. This query updates values of specified columns to the values of corresponding expressions in rows for which the `filter_expr` takes a non-zero value. Values are casted to the column type using the `CAST` operator. Updating columns that are used in the calculation of the primary or the partition key is not supported.
The `filter_expr` must be of type UInt8. This query updates values of specified columns to the values of corresponding expressions in rows for which the `filter_expr` takes a non-zero value. Values are casted to the column type using the `CAST` operator. Updating columns that are used in the calculation of the primary or the partition key is not supported.
```sql
ALTER TABLE [db.]table MATERIALIZE INDEX name IN PARTITION partition_name