For those who don't know, Goetz Graefe is sort of the patron saint of btrees. He recently won the Sigmod Codd innovations award for his contributions:<p><a href="https://sigmod.org/sigmod-awards/people/goetz-graefe-2017-sigmod-edgar-f-codd-innovations-award/" rel="nofollow">https://sigmod.org/sigmod-awards/people/goetz-graefe-2017-si...</a><p>He also has a lot to say about locking in B-trees:<p><a href="http://15721.courses.cs.cmu.edu/spring2016/papers/a16-graefe.pdf" rel="nofollow">http://15721.courses.cs.cmu.edu/spring2016/papers/a16-graefe...</a>
> Probably the strongest arguments for B-trees over hash indexes pertain to multi-field indexes and to nonuniform distributions of key values. A hash index on multiple fields requires search keys for all those fields such that a hash value can be calculated. A B-tree index, on the other hand, can efficiently support exact-match queries for a prefix of the index key, i.e., any number of leading index fields<p>Yes, well, if none of the columns/fields in the index are sufficiently selective, then the ability to search a B-tree by prefix may not do you much good. Don't get me wrong though: I fully agree with all of the given reasons for B-tree superiority to hash tables.<p>Although the newest storage technologies (particularly very fast byte-addressable NVMs) -- too new for TFA -- might well change things. When you have fast byte-addressable storage it will pay to not read pages, and hash tables may yet involve fewer accesses than B-trees in that case, though I suspect B-trees will successfully adapt anyways.
Well, it's an interesting survey. I'm surprised at how much space it devoted to illustrating B-trees in the context of RDBMSs as a lot of the concepts there really had no specific connection to B-trees.<p>So much space devoted to logging, locking and latches. All heavily used in the industry up till the last decade. All obsolete now. Not a single mention of immutable/persistent B-trees. Were there really no academic papers on the topic written in a time covered by this survey?
This is from 2011, in case you missed that. I was confused by sentences like:<p>>Flash memory, flash devices, and other solid state storage technology are about to change the memory hierarchy in computer systems in general and in data management in particular.<p>until I looked up at the publication date.