Over at pgsql-general, Bráulio Bhavamitra asks:
I wonder if there is any plans to move postgresql entirely to a columnar store (or at least make it an option), maybe for version 10?
This is a pretty interesting question. Completely replacing the current row-based store wouldn’t be a good idea: it has served us extremely well and I’m pretty sure that replacing it entirely with a columnar store would be disastrous performance-wise for OLTP use cases.
Some columns. Picture courtesy of Yiming Sun on Flickr
That doesn’t mean columnar stores are a bad idea in general — because they aren’t. They just have a more limited use case than “the whole database”. For analytical queries on append-mostly data, a columnar store is a much more appropriate representation than the regular row-based store, but not all databases are analytical.
However, in order to attain interesting performance gains you need to do a lot more than just change the underlying storage: you need to ensure that the rest of the system can take advantage of the changed representation, so that it can execute queries optimally; for instance, you may want aggregates that operate in a SIMD mode rather than one-value-at-a-time as it is today. This, in itself, is a large undertaking, and there are other challenges too.
As it turns out, there’s a team at 2ndQuadrant working precisely on these matters. We posted a patch last year, but it wasn’t terribly interesting — it only made a single-digit percentage improvement in TPC-H scores; not enough to bother the development community with (it was a fairly invasive patch). We want more than that.
In our design, columnar or not is going to be an option: you’re going to be able to say Dear server, for this table kindly set up columnar storage for me, would you? Thank you very much. And then you’re going to get a table which may be slower for regular usage but which will rock for analytics. For most of your tables the current row-based store will still likely be the best option, because row-based storage is much better suited to the more general cases.
We don’t have a timescale yet. Stay tuned.