In Oracle Database 23ai, significant improvements have been made to Hybrid Columnar Compression (HCC), with the default compression method now utilizing Zstandard (Zstd) instead of the previous algorithms, zlib and bzip2. But what exactly is Zstandard, and how does it differ from zlib and bzip2?
Zstandard is a lossless data compression algorithm developed by Yann Collet at Facebook. Since its open-source release in 2016, it has gained popularity for its efficiency and performance. You can find the source code here.(https://github.com/facebook/zstd)
Zstandard typically outperforms both zlib and bzip2 in terms of speed and efficiency. One of its standout features is its rapid compression and decompression capabilities. For instance, Zstd can decompress data at speeds around 550 MB/s, significantly faster than alternatives like zlib.
This impressive performance is one of the reasons Oracle has adopted Zstandard as the default compression method in version 23ai.
To take advantage of this new feature, you need to set the database “compatible” parameter to “23.0.0.0” . For tables that were compressed using previous versions (with zlib or bzip2), the existing format will be retained. If you want to utilize Zstandard for these tables, you can use the “ALTER TABLE MOVE” command to trigger recompression.
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