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slug | sidebar_position | sidebar_label |
---|---|---|
/en/sql-reference/statements/alter/ttl | 44 | TTL |
Manipulations with Table TTL
MODIFY TTL
You can change table TTL with a request of the following form:
ALTER TABLE [db.]table_name [ON CLUSTER cluster] MODIFY TTL ttl_expression;
REMOVE TTL
TTL-property can be removed from table with the following query:
ALTER TABLE [db.]table_name [ON CLUSTER cluster] REMOVE TTL
Example
Consider the table with table TTL
:
CREATE TABLE table_with_ttl
(
event_time DateTime,
UserID UInt64,
Comment String
)
ENGINE MergeTree()
ORDER BY tuple()
TTL event_time + INTERVAL 3 MONTH
SETTINGS min_bytes_for_wide_part = 0;
INSERT INTO table_with_ttl VALUES (now(), 1, 'username1');
INSERT INTO table_with_ttl VALUES (now() - INTERVAL 4 MONTH, 2, 'username2');
Run OPTIMIZE
to force TTL
cleanup:
OPTIMIZE TABLE table_with_ttl FINAL;
SELECT * FROM table_with_ttl FORMAT PrettyCompact;
Second row was deleted from table.
┌─────────event_time────┬──UserID─┬─────Comment──┐
│ 2020-12-11 12:44:57 │ 1 │ username1 │
└───────────────────────┴─────────┴──────────────┘
Now remove table TTL
with the following query:
ALTER TABLE table_with_ttl REMOVE TTL;
Re-insert the deleted row and force the TTL
cleanup again with OPTIMIZE
:
INSERT INTO table_with_ttl VALUES (now() - INTERVAL 4 MONTH, 2, 'username2');
OPTIMIZE TABLE table_with_ttl FINAL;
SELECT * FROM table_with_ttl FORMAT PrettyCompact;
The TTL
is no longer there, so the second row is not deleted:
┌─────────event_time────┬──UserID─┬─────Comment──┐
│ 2020-12-11 12:44:57 │ 1 │ username1 │
│ 2020-08-11 12:44:57 │ 2 │ username2 │
└───────────────────────┴─────────┴──────────────┘
See Also
- More about the TTL-expression.
- Modify column with TTL.