AWS Documentation » Amazon Redshift » Database Developer Guide » Designing Tables » Choosing a Column Compression Type » Compression Encodings

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Compression Encodings

Topics

• Raw Encoding
• Byte-Dictionary Encoding
• Delta Encoding
• LZO Encoding
• Mostly Encoding
• Runlength Encoding
• Text255 and Text32k Encodings
• Zstandard Encoding

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:

• Columns that are defined as sort keys are assigned RAW compression.

• Columns that are defined as BOOLEAN, REAL, or DOUBLE PRECISION data types are assigned RAW compression.

• 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