add_compression_policy()
communityCommunity functions are available under Timescale Community Edition. Click to learn more.Allows you to set a policy by which the system compresses a chunk automatically in the background after it reaches a given age.
Compression policies can only be created on hypertables or continuous aggregates
that already have compression enabled. To set timescaledb.compress and other
configuration parameters for hypertables, use the
ALTER TABLE
command. To enable compression on continuous aggregates, use the
ALTER MATERIALIZED VIEW
command. To view the policies that you set or the policies that already exist,
see informational views.
| Name | Type | Description |
|---|---|---|
hypertable | REGCLASS | Name of the hypertable or continuous aggregate |
compress_after | INTERVAL or INTEGER | The age after which the policy job compresses chunks. compress_after is calculated relative to the current time, so chunks containing data older than now - {compress_after}::interval are compressed. This argument is mutually exclusive with compress_created_before. |
compress_created_before | INTERVAL | Chunks with creation time older than this cut-off point are compressed. The cut-off point is computed as now() - compress_created_before. Defaults to NULL. Not supported for continuous aggregates yet. This argument is mutually exclusive with compress_after. |
The compress_after parameter should be specified differently depending
on the type of the time column of the hypertable or continuous aggregate:
- For hypertables with TIMESTAMP, TIMESTAMPTZ, and DATE time columns: the time interval should be an INTERVAL type.
- For hypertables with integer-based timestamps: the time interval should be an integer type (this requires the integer_now_func to be set).
| Name | Type | Description |
|---|---|---|
schedule_interval | INTERVAL | The interval between the finish time of the last execution and the next start. Defaults to 12 hours for hyper tables with a chunk_time_interval >= 1 day and chunk_time_interval / 2 for all other hypertables. |
initial_start | TIMESTAMPTZ | Time the policy is first run. Defaults to NULL. If omitted, then the schedule interval is the interval from the finish time of the last execution to the next start. If provided, it serves as the origin with respect to which the next_start is calculated |
timezone | TEXT | A valid time zone. If initial_start is also specified, subsequent executions of the compression policy are aligned on its initial start. However, daylight savings time (DST) changes may shift this alignment. Set to a valid time zone if this is an issue you want to mitigate. If omitted, UTC bucketing is performed. Defaults to NULL. |
if_not_exists | BOOLEAN | Setting to true causes the command to fail with a warning instead of an error if a compression policy already exists on the hypertable. Defaults to false. |
Add a policy to compress chunks older than 60 days on the cpu hypertable.
SELECT add_compression_policy('cpu', compress_after => INTERVAL '60d');
Add a policy to compress chunks created 3 months before on the 'cpu' hypertable.
SELECT add_compression_policy('cpu', compress_created_before => INTERVAL '3 months');
Note above that when compress_after is used then the time data range
present in the partitioning time column is used to select the target
chunks. Whereas, when compress_created_before is used then the chunks
which were created 3 months ago are selected.
Add a compress chunks policy to a hypertable with an integer-based time column:
SELECT add_compression_policy('table_with_bigint_time', BIGINT '600000');
Add a policy to compress chunks of a continuous aggregate called cpu_weekly, that are
older than eight weeks:
SELECT add_compression_policy('cpu_weekly', INTERVAL '8 weeks');
Keywords
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