With standard multivalue compression, compressed data values can be accessed without decompression processing overhead. Vantage need not decompress blocks or other large chunks of data to be able to access a single row or value. This removes the significant CPU cost tradeoff common to most compression implementations.
The following rules apply to multivalue and algorithmic compression.
- For table columns, you can specify multivalue compression, algorithmic compression, or both.
- If you specify multivalue and algorithmic compression for a column, you can specify the options in any order: multivalue compression followed by algorithmic compression or algorithmic compression followed by multivalue compression.
- When you specify multivalue compression and algorithmic compression on the same column, Vantage applies algorithmic compression only to values that are not also specified for multivalue compression.
- Specifying algorithmic compression alone or in combination with multivalue compression for a column has the following data type size limitations:
Type of Column Compression Data Type Size Algorithmic only Has no limit. Algorithmic and multivalue Limited by the maximum valid size for multivalue compression. - You cannot specify multivalue compression or algorithmic compression on a column that is a component of the primary index or primary AMP index for a table.
- You can specify multivalue compression and algorithmic compression on a column that is a component of a secondary index for a table.
- You can specify multivalue compression, algorithmic compression, or both on a column that is a component of a referential integrity constraint.
- You can specify multivalue compression, algorithmic compression, or both on the columns of nonpartitioned data tables and global temporary tables.
- Algorithmic compression and multivalue compression are supported by default for the columns of spools. If a column is defined with multivalue compression, algorithmic compression, or both, the compression defined for the column is inherited for the spool column.
- You can copy the definition of a table to a different name using the COPY TABLE … AS option, and the target table retains the algorithmic or multivalue compression defined for the source table.