Byte-dictionary encoding - Amazon Redshift

In byte dictionary encoding, a separate dictionary of unique values is created for each block of column values on disk. (An Amazon Redshift disk block occupies 1 MB.) The dictionary contains up to 256 one-byte values that are stored as indexes to the original data values. If more than 256 values are stored in a single block, the extra values are written into the block in raw, uncompressed form. Th

[yass]

" This encoding is very effective when a column contains a limited number of unique values. This encoding is optimal when the data domain of a column is fewer than 256 unique values. Byte dictionary encoding is especially space-efficient if the column holds long character strings. "