Compression Encodings
Topics
A compression encoding specifies the type of compression that is applied to a column of data values as rows are added to a table.
If no compression is specified in a CREATE TABLE or ALTER TABLE statement, Amazon Redshift automatically assigns compression encoding as follows:
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Columns that are defined as sort keys are assigned RAW compression.
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Columns that are defined as BOOLEAN, REAL, or DOUBLE PRECISION data types are assigned RAW compression.
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All other columns are assigned LZO compression.
The following table identifies the supported compression encodings and the data types that support the encoding.
| Encoding type | Keyword in CREATE TABLE and ALTER TABLE | Data types |
|---|---|---|
| Raw (no compression) | RAW | All |
| Byte dictionary | BYTEDICT | All except BOOLEAN |
| Delta |
DELTA DELTA32K |
SMALLINT, INT, BIGINT, DATE, TIMESTAMP, DECIMAL INT, BIGINT, DATE, TIMESTAMP, DECIMAL |
| LZO | LZO | All except BOOLEAN, REAL, and DOUBLE PRECISION |
| Mostlyn |
MOSTLY8 MOSTLY16 MOSTLY32 |
SMALLINT, INT, BIGINT, DECIMAL INT, BIGINT, DECIMAL BIGINT, DECIMAL |
| Run-length | RUNLENGTH | All |
| Text |
TEXT255 TEXT32K |
VARCHAR only VARCHAR only |
| Zstandard | ZSTD | All |
