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DOCAPI-5753: Description of use_minimalistic_part_header_in_zookeeper (#4651)

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BayoNet 2019-03-21 17:57:17 +03:00 committed by Ivan Blinkov
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docs/en/operations/server_settings/settings.md
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@ -707,4 +707,32 @@ For more information, see the section "[Replication](../../operations/table_engi
</zookeeper>
```
## use_minimalistic_part_header_in_zookeeper {#server-settings-use_minimalistic_part_header_in_zookeeper}
Storage method of the data parts headers in ZooKeeper.
This setting applies only to the `MergeTree`-family and it can be specified:
- Globally in the [merge_tree](#server_settings-merge_tree) section of the `config.xml` file.
ClickHouse uses the setting for all the tables on the server. You can change the setting at any time. Existing tables change their behavior with the setting change.
- For each individual table.
When creating a table, specify the corresponding [engine setting](../table_engines/mergetree.md#table_engine-mergetree-creating-a-table). After creating a table you can't change its behavior even with the global setting.
**Possible values**
- 0 — Functionality is turned off.
- 1 — Functionality is turned on.
If `use_minimalistic_part_header_in_zookeeper = 1`, then [replicated](../table_engines/replication.md) tables store the headers of the data parts compactly using single `znode`. If the table contains many columns, this way of storage significantly reduces the volume of the data stored in Zookeeper.
!!! attention
Ones applying the `use_minimalistic_part_header_in_zookeeper = 1` you can't degrade the ClickHouse server to the version that doesn't support this setting. Be careful when upgrading ClickHouse on servers of a cluster. Don't upgrade all the servers at ones. It is safer to test the new versions of ClickHouse in a test environment, or at least at some servers of a cluster.
The data parts headers already stored with this setting also can't be restored to previous (non-compact) representation.
**Default value:** 0.
[Original article](https://clickhouse.yandex/docs/en/operations/server_settings/settings/) <!--hide-->

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docs/en/operations/table_engines/mergetree.md
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@ -70,9 +70,9 @@ For a description of request parameters, see [request description](../../query_l
- `SETTINGS` — Additional parameters that control the behavior of the `MergeTree`:
- `index_granularity` — The granularity of an index. The number of data rows between the "marks" of an index. By default, 8192. The list of all available parameters you can see in [MergeTreeSettings.h](https://github.com/yandex/ClickHouse/blob/master/dbms/src/Storages/MergeTree/MergeTreeSettings.h).
- `use_minimalistic_part_header_in_zookeeper` — Storage method of the data parts headers in ZooKeeper. If `use_minimalistic_part_header_in_zookeeper=1`, then ZooKeeper stores less data. For more information refer the [setting description](../server_settings/settings.md#server-settings-use_minimalistic_part_header_in_zookeeper) in the "Server configuration parameters" chapter.
- `min_merge_bytes_to_use_direct_io` — The minimum data volume for merge operation required for using of the direct I/O access to the storage disk. During the merging of the data parts, ClickHouse calculates summary storage volume of all the data to be merged. If the volume exceeds `min_merge_bytes_to_use_direct_io` bytes, thеn ClickHouse reads and writes the data using direct I/O interface (`O_DIRECT` option) to the storage disk. If `min_merge_bytes_to_use_direct_io = 0`, then the direct I/O is disabled. Default value: `10 * 1024 * 1024 * 1024` bytes.
**Example of sections setting**
```