September 7, 2011
Vertica projections — an overview
Partially at my suggestion, Vertica has blogged a three-part series explaining the “projections” that are central to a Vertica database. This is important, because in Vertica projections play the roles that in many analytic DBMS might be filled by base tables, indexes, AND materialized views. Highlights include:
- A Vertica projection can contain:
- All the columns in a table.
- Some of the columns in a table.
- A prejoin among tables.
- Vertica projections are updated and maintained just as base tables are. (I.e., there’s no kind of batch lag.)
- You can import the same logical schema you use elsewhere. Vertica puts no constraints on your logical schema. Note: Vertica has been claiming good support for all logical schemas since Vertica 4.0 came out in early 2010.
- Vertica (the product) will automatically generate a physical schema for you — i.e. a set of projections — that Vertica (the company) thinks will do a great job for you. Note: That also dates back to Vertica 4.0.
- Vertica claims that queries are very fast even when you haven’t created projections explicitly for them. Note: While the extent to which this is true may be a matter of dispute, competitors clearly overreach when they make assertions like “every major Vertica query needs a projection prebuilt for it.”
- On the other hand, it is advisable to build projections (automatically or manually) that optimize performance of certain parts of your query load.
The blog posts contain a lot more than that, of course, both rah-rah and technical detail, including reminders of other Vertica advantages (compression, no logging, etc.). If you’re interested in analytic DBMS, they’re worth a look.
Categories: Columnar database management, Data warehousing, Vertica Systems
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Many of the companies I write about are clients, including Vertica.