Codecs
| Codec Name | Recommended Data Types | Performance Notes |
|---|---|---|
| LZ4 | Any | Used by default. Extremely fast; good compression; balanced speed and efficiency |
| ZSTD(level) | Any | Good compression; pretty fast; best for high compression needs. Don’t use levels higher than 3. |
| LZ4HC(level) | Any | LZ4 High Compression algorithm with configurable level; slower but better compression than LZ4, but decompression is still fast. |
| Delta | Integer Types, Time Series Data, Timestamps | Preprocessor (should be followed by some compression codec). Stores difference between neighboring values; good for monotonically increasing data. |
| DoubleDelta | Integer Types, Time Series Data | Stores difference between neighboring delta values; suitable for time series data |
| Gorilla | Floating Point Types | Calculates XOR between current and previous value; suitable for slowly changing numbers |
| T64 | Integer, Time Series Data, Timestamps | Preprocessor (should be followed by some compression codec). Crops unused high bits; puts them into a 64x64 bit matrix; optimized for 64-bit data types |
| GCD | Integer Numbers | Preprocessor (should be followed by some compression codec). Greatest common divisor compression; divides values by a common divisor; effective for divisible integer sequences |
| FPC | Floating Point Numbers | Designed for Float64; Algorithm detailed in FPC paper, ClickHouse® PR #37553 |
| ZSTD_QAT | Any | Requires hardware support for QuickAssist Technology (QAT) hardware; provides accelerated compression tasks |
| DEFLATE_QPL | Any | Requires hardware support for Intel’s QuickAssist Technology for DEFLATE compression; enhanced performance for specific hardware |
| LowCardinality | String | It’s not a codec, but a datatype modifier. Reduces representation size; effective for columns with low cardinality |
| NONE | Non-compressable data with very high entropy, like some random string, or some AggregateFunction states | No compression at all. Can be used on the columns that can not be compressed anyway. |
See
How to test different compression codecs
https://altinity.com/blog/2019/7/new-encodings-to-improve-clickhouse
https://www.percona.com/sites/default/files/ple19-slides/day1-pm/clickhouse-for-timeseries.pdf