Compression encodings
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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Columns that are defined as SMALLINT, INTEGER, BIGINT, DECIMAL, DATE, TIMESTAMP, or TIMESTAMPTZ data types are assigned AZ64 compression.
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Columns that are defined as CHAR or VARCHAR data types are assigned LZO compression.
Topics
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 |
| AZ64 | AZ64 | SMALLINT, INTEGER, BIGINT, DECIMAL, DATE, TIMESTAMP, TIMESTAMPTZ |
| Byte dictionary | BYTEDICT | SMALLINT, INTEGER, BIGINT, DECIMAL, REAL, DOUBLE PRECISION, CHAR, VARCHAR, DATE, TIMESTAMP, TIMESTAMPTZ |
| Delta |
DELTA DELTA32K |
SMALLINT, INT, BIGINT, DATE, TIMESTAMP, DECIMAL INT, BIGINT, DATE, TIMESTAMP, DECIMAL |
| LZO | LZO | SMALLINT, INTEGER, BIGINT, DECIMAL, CHAR, VARCHAR, DATE, TIMESTAMP, TIMESTAMPTZ |
| Mostlyn |
MOSTLY8 MOSTLY16 MOSTLY32 |
SMALLINT, INT, BIGINT, DECIMAL INT, BIGINT, DECIMAL BIGINT, DECIMAL |
| Run-length | RUNLENGTH | SMALLINT, INTEGER, BIGINT, DECIMAL, REAL, DOUBLE PRECISION, BOOLEAN, CHAR, VARCHAR, DATE, TIMESTAMP, TIMESTAMPTZ |
| Text |
TEXT255 TEXT32K |
VARCHAR only VARCHAR only |
| Zstandard | ZSTD | SMALLINT, INTEGER, BIGINT, DECIMAL, REAL, DOUBLE PRECISION, BOOLEAN, CHAR, VARCHAR, DATE, TIMESTAMP, TIMESTAMPTZ |
