Oracle Database 11g Release 2 is out, and as usual I wasn’t briefed — perhaps because Oracle is more scared than its competitors are of hard questions, perhaps for some other reason entirely.* Anyhow, Oracle Database 11 Release 2 contains an Exadata-only feature called hybrid columnar compression. The Oracle Database 11g Release 2 white paper says “data is grouped, ordered, and stored one column at a time.” But Kevin Closson clarifies:
The word hybrid is important.
Rows are still used. They are stored in an object called a Compression Unit. Compression Units can span multiple blocks. Like values are stored in the compression unit with metadata that maps back to the rows.
So, “hybrid” is the word. But, none of that matters as much as the effectiveness. This form of compression is extremely effective.
That sounds a whole lot like PAX. Specifically, in Oracle’s case I would guess “hybrid columnar compression” provides the compression benefits of column stores, but not column stores’ I/O benefits, and also not any kind of in-memory compression.
*Actually, Oracle has indicated to me multiple times that the reason is I won’t let Oracle review what I write before I publish it. My stance is that such “review” is an extremely time-wasting courtesy, in which one spends a lot of time diplomatically explaining to a vendor that, contrary to what it hopes, one really does know the difference between marketing puffery and sober fact. I rarely do white paper projects any more, notwithstanding that my fee for those now exceeds $2,000/page. I’m not about to go through the “review” hassle for something I write for free, about a vendor who isn’t otherwise a paying client.