16.20 - SHOWCOMPRESS Enhancements - Teradata Vantage NewSQL Engine

Teradata Vantageā„¢ NewSQL Engine Release Summary

prodname
Teradata Database
Teradata Vantage NewSQL Engine
vrm_release
16.20
created_date
March 2019
category
Release Notes
featnum
B035-1098-162K
The Ferret SHOWCOMPRESS command has two new output display options that provide additional information about table data compression:
  • /S displays the table ID's, table name and subtable ID's of the compressed and uncompressed tables.
  • /L displays the compression state, compression algorithm, compression level, exact compression ratio, exact % of blocks, exact used GB, and exact % of data, in addition to the information provided by the /S option.

Benefits

  • The new /L display option allows you to determine exactly how much data in a table is compressed and uncompressed, and the exact compression ratio. (The related SHOWBLOCKS command provides only estimates based on a small sample of the table data.)
  • Because the /L option displays the algorithm used to compress the data, you can:
    • Validate that the correct algorithm has been used based on the data types of the table columns
    • Compare the space-saving benefits of different compression algorithms

Considerations

  • SHOWCOMPRESS /L can require a long time for large systems, because it must traverse each data block to obtain exact compression statistics.

Additional Information

For more information on block-level compression, see Teradata Vantageā„¢ - Database Design, B035-1094.