CODEC

CREATE TABLE codec_example
(
    dt Date CODEC(ZSTD),
    ts DateTime CODEC(LZ4HC),
    float_value Float32 CODEC(NONE),
    double_value Float64 CODEC(LZ4HC(9)),
    value Float32 CODEC(Delta, ZSTD)
)
ENGINE = <Engine>
...

ALTER TABLE codec_example MODIFY COLUMN float_value CODEC(Default);

CREATE TABLE codec_example
(
    timestamp DateTime CODEC(DoubleDelta),
    slow_values Float32 CODEC(Gorilla)
)
ENGINE = MergeTree()

SET enable_quantized_codec = 1;

CREATE TABLE vectors
(
    id UInt32,
    vec Array(BFloat16) CODEC(Quantized('rabitq', 1536))
)
ENGINE = MergeTree ORDER BY id;

CREATE TABLE mytable
(
    x String CODEC(AES_128_GCM_SIV)
)
ENGINE = MergeTree ORDER BY x;

CREATE TABLE mytable
(
    x String CODEC(Delta, LZ4, AES_128_GCM_SIV)
)
ENGINE = MergeTree ORDER BY x;

CREATE TABLE adaptive
(
    time DateTime,
    user_id UInt64
)
ENGINE = MergeTree
ORDER BY time
SETTINGS enable_adaptive_codec_selection = 1;

INSERT INTO adaptive SELECT toDateTime('2026-01-01') + number, cityHash64(number) FROM numbers(1000000);
OPTIMIZE TABLE adaptive FINAL;

SELECT column, codec_block_counts FROM mergeTreeCodecBlockCounts(currentDatabase(), 'adaptive');

   ┌─column──┬─codec_block_counts─┐
1. │ time    │ {'T64':62}         │
2. │ user_id │ {'NONE':123}       │
   └─────────┴────────────────────┘