People here are comparing vanilla MySQL to vanilla Postgres. Both are row-oriented, general purpose relational databases. Citus is specifically optimised for analytics, and is not a drop-in replacement for either MySQL or Postgres. From their FAQ:

"it is a great fit for ad-hoc, real-time analytics on timeseries data, but not ideal as the transactional backbone of your credit card processing system"

I've no experience with Citus, but on the MySQL side I have a lot of experience with Infobright. It might be a better application to compare against Citus. It's single-server, massively faster than MySQL for analytics work, but also comes with a number of caveats that make it unsuitable to be a general purpose database. Great for analytics, though.

Couple of things.

1) CitusDB is not single server. It's multiple server. I have queries which destroy a single MySQL or single Postgres server.

2) Postgres 9.5 comes with using multiple cores. That's DEFAULT. Did you miss the link of Parallel Sequential Scan?

Postgres 9.5 Vanilla is going to out-do MySQL just on this alone.

I know some MySQL guys who wanted to go with Citus but couldnt because it was too expensive. Now looking at the Parallel Sequential Scan, it's showing some major successes. Trust me, once they get this right. 9.6/9.7 could be stuff like Postgres XL that is native. That's right, bye bye MySQL vanilla. It's was nice to know you.

For the record, I think Postgres is an all-round better database than MySQL. I've experience with both in large production deployments.

I still think that's not fair to compare MySQL to Citus DB. That's the point I was trying to make. Citus is a multi-server MPP database for analytics. MySQL doesn't have a player in that game. I would certainly be interested to see a (fair) comparison between Citus, Redshift, Vertica, Teradata, Greenplum, Snowflake etc... but that's a different thing.

Parallel Sequential Scan sounds great, but it's not here yet. When it is, we can see whether it makes Postgres a one-stop solution for both traditional, transactional work as well as analytics (which tends to do better on column-oriented stores)

I don't think it's fair to compare Citus DB to MySQL either.

I never did. I just stated my experience and you READ that as a comparison. Due to me mentioning MPP, I then lead with PSS. See how that works?

I mention MPP and PSS to inform people who are on MySQL and looking to change. I don't think MySQL will come with native MPP or PSS because of licensing issues (I may be wrong).

There is shard query with MySQL which is a percona effort. But there are too many moving parts for a production env.

Finally, I'm not too bothered about other offerings in the MPP space. I'm already paying a license fee and reaping the rewards. It's good enough for me and was able to hit the ground running very very quickly.

> I switched from MySQL to Postgres. Specifically, we are using CitusDB. The performance we are getting is nothing but staggering, due to MPP.

You are talking about switching between them and even concluded, "I don't know of any valid reasons why anyone would switch back."

It might not be what you meant, but to me, it also reads as if you're comparing MySQL to CitusDB.