98 lines
3.6 KiB
Markdown
98 lines
3.6 KiB
Markdown
---
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{
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"title": "Time zone",
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"language": "en"
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}
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---
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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# Time zone
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Doris supports multiple time zone settings
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## Noun Interpretation
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* FE: Frontend, the front-end node of Doris. Responsible for metadata management and request access.
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* BE: Backend, Doris's back-end node. Responsible for query execution and data storage.
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## Basic concepts
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There are multiple time zone related parameters in Doris
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* `system_time_zone`:
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When the server starts, it will be set automatically according to the time zone set by the machine, which can not be modified after setting.
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* `time_zone`:
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Server current time zone, set it at session level or global level.
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## Specific operations
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1. `SHOW VARIABLES LIKE '% time_zone%'`
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View the current time zone related configuration
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2. `SET time_zone = 'Asia/Shanghai'`
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This command can set the session level time zone, which will fail after disconnection.
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3. `SET global time_zone = 'Asia/Shanghai'`
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This command can set time zone parameters at the global level. The FE will persist the parameters and will not fail when the connection is disconnected.
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### Impact of time zone
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Time zone setting affects the display and storage of time zone sensitive values.
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It includes the values displayed by time functions such as `NOW()` or `CURTIME()`, as well as the time values in `SHOW LOAD` and `SHOW BACKENDS` statements.
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However, it does not affect the `LESS THAN VALUE` of the time-type partition column in the `CREATE TABLE` statement, nor does it affect the display of values stored as `DATE/DATETIME` type.
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Functions affected by time zone:
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* `FROM_UNIXTIME`: Given a UTC timestamp, return the date and time of the specified time zone, such as `FROM_UNIXTIME(0)`, return the CST time zone: `1970-01-08:00`.
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* `UNIX_TIMESTAMP`: Given a specified time zone date and time, return UTC timestamp, such as CST time zone `UNIX_TIMESTAMP('1970-01 08:00:00')`, return `0`.
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* `CURTIME`: Returns the datetime of specified time zone.
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* `NOW`: Returns the specified date and time of specified time zone.
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* `CONVERT_TZ`: Converts a date and time from one specified time zone to another.
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## Restrictions
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Time zone values can be given in several formats, case-insensitive:
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* A string representing UTC offset, such as '+10:00' or '-6:00'.
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* Standard time zone formats, such as "Asia/Shanghai", "America/Los_Angeles"
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* Abbreviated time zone formats such as MET and CTT are not supported. Because the abbreviated time zone is ambiguous in different scenarios, it is not recommended to use it.
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* In order to be compatible with Doris and support CST abbreviated time zone, CST will be internally transferred to "Asia/Shanghai", which is Chinese standard time zone.
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## Time zone format list
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[List of TZ database time zones] (https://en.wikipedia.org/wiki/List_of_tz_database_time_zones)
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[Edit on GitHub](https://github.com/apache/incubator-doris/blob/master/docs/documentation/en/administrator-guide/time-zone_EN.md) |