Read-only performance for unknown kind of query with unknown size of dataset using memory-cache plugin.
Hmmm… I don't see any meaningful information. Should I be impressed? Am I missing something?
Hmmm… I don't see any meaningful information. Should I be impressed? Am I missing something?
Historically the overhead of SQL put a low ceiling on the potential performance of simple queries. Which is exactly why KV databases appeared in the first place, because a scalar value get in most RDBMS systems barely hit 1000 results per second, and that is being optimistic. That overhead was never optimized away because the classic use of the RDBMS was query conversations where each interaction was very expensive (e.g. large, complex queries), so optimizing it wasn't important.
But, thanks to competition, most database systems have gotten fantastically more performant. Even using the TDS interface, I can get close to Redis performance with SQL Server now, while it was beaten by one if not two orders of magnitude a few versions ago. And in this case MySQL added the ability to use a much simpler, lighter memcached API in from of MySQL, for obvious reason -- the underlying database system is fast enough that it is of value.
I should add that almost everyone who has commented thus far completely misunderstands what this is taking about. It is the Memcached API atop MySQL. Meaning you can talk to your database server through that API from any client programmed to talk to a memcached server. And that same data that you access via memcached (reading or writing) can be accessed in your normal SQL. Which is pretty cool.
I dug MySQL 5.7 manual several times, but I couldn't find any proof that this is just an memcache API atop MySQL.
But I found some proof that says there's a real memcache daemon atop MySQL.
> Running memcached in the same process space as the MySQL server avoids the network overhead of passing requests back and forth.
MySQL 5.7 manual clarifies that they're running memcache daemon inside the database engine in-process mode. So actually real memcache is serving the data atop the engine.
So, if dataset is read-only and small enough, it's likely to happen that whole the data is being served by memcache. In that case, it cannot be slower than memcache.
That's why I couldn't be impressed. The only thing MySQL doing is automatic handling of memcache daemon. That should be convenient, but not impressive.
Maybe I am wrong. If you think I am wrong, please show me some reference that explicitly mentions this is just API, and there's no running memcache instance.
Also, regardless of whatever is really happening under hood, this benchmark is still meaningless. Because database exists to store data and all the hard stuffs are only happening when storing data. Writing transactions usually degrade performance a lot. That's why writing transactions must be included in benchmark to show the real world performance.
https://dev.mysql.com/doc/refman/5.6/en/innodb-memcached-ben...
Yes, there is a memcached "daemon" in the sense that they run a memcached host within mysql, which they obviously have to do. That memcached "instance" reads and writes from InnoDB and the shared buffer pool also used by the SQL engine: It does not maintain a unique memory instance, and values read or written are atomically consistent with the mySQL instance.
The single and only reason this product exists is that the memcached API is much simpler and network/parsing efficient, allowing for much better round-trip-times when doing simple queries.
> You do not need to manually load data into memcached at startup. As particular keys are requested by an application, the values are retrieved from the database automatically, and cached in memory using the InnoDB buffer pool.
So memory-cache is provided the engine itself, not by external plugin.
I am not doubting but just honestly asking. I've been discussing a possible Redis solution for complementing our current SQL Server.
Our problem isn't that big, we need to serve 10k req/sec of a simple query, can SQL Server do that? Isn't the connection pool the bottleneck to handle loads of this scale?
Several years ago with SQL Server 2008 R2 I achieved 200,000+ simple queries per second (http://bit.ly/IlH2id -- this is not a regimented benchmark by any measure of the imagination, but is only saying "validate before assuming" because you might find your install performs far better than you anticipate) using the standard TDS query interface. This was on pretty beefy hardware, and is obviously enormously contingent on the data being in memory (which you can force with 2012), however it blew me away and completely undermined an initiative we had to implement AppFabric / Redis or other solutions.
What is the mechanism to do this in MSSQL 2012?
Is Hekaton the feature you are referring to?