Guidelines for Specifying Compression for Column-Partitioned Tables and Join Indexes - Teradata Database

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Guidelines for Specifying Compression for Column‑Partitioned Tables and Join Indexes

  • If autocompression is effective for a column, put that column into a single‑column partition even if it is not frequently accessed.
  • If autocompression on the individual columns or subsets of columns is not effective, you should group columns into a column partition when those columns are always or frequently accessed together by queries or are infrequently accessed.
  • If autocompression is not effective for a column partition, specify NO AUTO COMPRESS for the column partition (with COLUMN format) to avoid the overhead of checking for autocompression opportunities when there are none to exploit.
  • Autocompression is most effective for single‑column partitions with COLUMN format, less so for multicolumn partitions (especially as the number of columns increases) with COLUMN format, but not effective for column partitions with ROW format.

  • Specify multivalue compression, algorithmic compression, or both for known high‑occurrence values for columns where compression can be effective. For example, if you know that the data for a column is limited to a few values, you should specify multi‑value compression for those values.
  • Specify an appropriate algorithmic compression for Unicode columns that contain a substantial number of compressible characters. The ASCII script (U+0000 to U+007F) of Unicode is compressible with the UTF8 algorithm.