Advanced usage of compression allows users to compress chunks manually, instead of automatically as they age.
Compressed chunks have the following limitations:
ROW LEVEL SECURITYis not supported.
UNIQUE) are restricted to compression
PRIMARY KEY) are restricted to compression
SEGMENTBYcolumns when applicable. Otherwise they are unsupported.
In general, compressing a hypertable does impose some limitations on the types of data modifications that can occur on data inside a compressed chunk. The table below provides a brief outline of allowed modifications based on the version of TimescaleDB you are currently running.
|TimscaleDB Version||Supported data modifications on compressed chunks|
|1.5 - 2.0||Data and schema modifications are not supported.|
|2.1 - 2.2||Schema may be modified on compressed hypertables. Data modification not supported.|
|2.3||Schema modifications and basic insert of new data are allowed. Deleting, updating and some advanced insert statements are not supported.|
Starting with TimescaleDB 2.1, users have the ability to modify the schema of hypertables that have compressed chunks. Specifically, you can add columns to and rename existing columns of such compressed hypertables.
Starting with TimescaleDB 2.3, users have the ability to insert data into compressed chunks and to enable compression policies on distributed hypertables.
Altering data of compressed chunks still has some limitations:
DELETEstatements on compressed chunks.
INSERTis not fully supported on compressed chunks:
ON CONFLICTclause i.e. upserts are not supported.
AFTER INSERTrow-level triggers (
FOR EACH ROW).
UNIQUE) are not supported.
PRIMARY KEY) are not supported.
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