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Added english documentation for extended TTL syntax (#8261)

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* Added english documentation for extended TTL syntax.

* Update docs/en/operations/table_engines/mergetree.md

Co-Authored-By: Ivan Blinkov <github@blinkov.ru>

* Added link to multiple volumes.

* Update docs/en/operations/table_engines/mergetree.md

Co-Authored-By: Ivan Blinkov <github@blinkov.ru>

* Update docs/en/operations/table_engines/mergetree.md

Co-Authored-By: Ivan Blinkov <github@blinkov.ru>

* Update docs/en/operations/table_engines/mergetree.md

Co-Authored-By: Ivan Blinkov <github@blinkov.ru>

* Changed deletion to removal.

* Removed redundant piece of text.
This commit is contained in:
Vladimir Chebotarev 2019-12-18 10:54:21 +03:00 committed by Ivan Blinkov
parent 6d58d85579
commit 292c38c514
1 changed files with 23 additions and 7 deletions
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docs/en/operations/table_engines/mergetree.md
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@ -41,7 +41,7 @@ CREATE TABLE [IF NOT EXISTS] [db.]table_name [ON CLUSTER cluster]
[ORDER BY expr]
[PRIMARY KEY expr]
[SAMPLE BY expr]
[TTL expr]
[TTL expr [DELETE|TO DISK 'xxx'|TO VOLUME 'xxx'], ...]
[SETTINGS name=value, ...]
```
@ -70,11 +70,13 @@ For a description of parameters, see the [CREATE query description](../../query_
If a sampling expression is used, the primary key must contain it. Example: `SAMPLE BY intHash32(UserID) ORDER BY (CounterID, EventDate, intHash32(UserID))`.
- `TTL` — An expression for setting storage time for rows.
- `TTL` — A list of rules specifying storage duration of rows and defining logic of automatic parts movement [between disks and volumes](#table_engine-mergetree-multiple-volumes).
It must have one `Date` or `DateTime` column as a result. Example:
Expression must have one `Date` or `DateTime` column as a result. Example:
`TTL date + INTERVAL 1 DAY`
Type of the rule `DELETE|TO DISK 'xxx'|TO VOLUME 'xxx'` specifies an action to be done with the part if the expression is satisfied (reaches current time): removal of expired rows, moving a part (if expression is satisfied for all rows in a part) to specified disk (`TO DISK 'xxx'`) or to volume (`TO VOLUME 'xxx'`). Default type of the rule is removal (`DELETE`). List of multiple rules can specified, but there should be no more than one `DELETE` rule.
For more details, see [TTL for columns and tables](#table_engine-mergetree-ttl)
- `SETTINGS` — Additional parameters that control the behavior of the `MergeTree`:
@ -371,9 +373,11 @@ Reading from a table is automatically parallelized.
Determines the lifetime of values.
The `TTL` clause can be set for the whole table and for each individual column. If both `TTL` are set, ClickHouse uses that `TTL` which expires earlier.
The `TTL` clause can be set for the whole table and for each individual column. Table-level TTL can also specify logic of automatic move of data between disks and volumes.
To define the lifetime of data, use expression evaluating to [Date](../../data_types/date.md) or [DateTime](../../data_types/datetime.md) data type, for example:
Expressions must evaluate to [Date](../../data_types/date.md) or [DateTime](../../data_types/datetime.md) data type.
Example:
```sql
TTL time_column
@ -428,7 +432,17 @@ ALTER TABLE example_table
**Table TTL**
When data in a table expires, ClickHouse deletes all corresponding rows.
Table can have an expression for removal of expired rows, and multiple expressions for automatic move of parts between [disks or volumes](#table_engine-mergetree-multiple-volumes). When rows in the table expire, ClickHouse deletes all corresponding rows. For parts moving feature, all rows of a part must satisfy the movement expression criteria.
```sql
TTL expr [DELETE|TO DISK 'aaa'|TO VOLUME 'bbb'], ...
```
Type of TTL rule may follow each TTL expression. It affects an action which is to be done once the expression is satisfied (reaches current time):
- `DELETE` - delete expired rows (default action);
- `TO DISK 'aaa'` - move part to the disk `aaa`;
- `TO VOLUME 'bbb'` - move part to the disk `bbb`.
Examples:
@ -443,7 +457,9 @@ CREATE TABLE example_table
ENGINE = MergeTree
PARTITION BY toYYYYMM(d)
ORDER BY d
TTL d + INTERVAL 1 MONTH;
TTL d + INTERVAL 1 MONTH [DELETE],
d + INTERVAL 1 WEEK TO VOLUME 'aaa',
d + INTERVAL 2 WEEK TO DISK 'bbb';
```
Altering TTL of the table