Expiring data with time-to-live
Use time-to-live (TTL) to expire data in a column or table.
Columns and tables support an optional expiration period called TTL (time-to-live); TTL is not supported on counter columns. Define the TTL value in seconds. Data expires after the data exceeds the TTL period and is then marked with a tombstone. Expired data continues to be available for read requests during the grace period, see gc_grace_seconds. Normal compaction and repair processes automatically remove the tombstone data.
- TTL precision is one second, which is calculated by the coordinator node. When specifying the TTL, ensure that all nodes in the cluster have synchronized clocks.
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A very short TTL is not useful.
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Expiring data uses additional 8 bytes of memory and disk space to record the TTL and grace period.
January 19 2038
03:14:07 UTC due to the Year 2038 problem. The TTL date overflow policy
determines whether requests with expiration timestamps later than the maximum
date are rejected or inserted. See -Dcassandra.expiration_date_overflow_policy.Setting a TTL for a specific column
Use CQL to set the TTL.
To change the TTL of a specific column, you must re-insert the data with a new TTL. The database upserts the column with the new TTL.
To remove the TTL from a column, set the TTL to zero. For details, see the UPDATE documentation.
Setting a TTL for a table
Use CREATE TABLE or ALTER TABLE to define the default_time_to_live property for all columns in a table. If any column exceeds the TTL, the entire row is deleted.
For details and examples, see Expiring data with TTL example.