Tab housekeeping but I also realise that people seem to have missed announcements, developments, etc. that have happened in the last couple of months (and boy have they been exciting). I think we definitely need something like the now-defunct MySQL Newsletter (and no, DB Weekly or NoSQL Weekly just don’t seem to cut it for me!).
MyRocks
During @scale (August 31), Yoshinori Matsunobu mentioned that MyRocks has been deployed in one region for 5% of its production workload at Facebook.
By October 4 at the Percona Live Amsterdam 2016 event, Percona CEO Peter Zaitsev said that MyRocks is coming to Percona Server (blog). On October 6, it was also announced that MyRocks is coming to MariaDB Server 10.2 (note I created MDEV-9658 back in February 2016, and that’s a great place to follow Sergei Petrunia’s progress!).
Rick Pizzi talks about MyRocks: migrating a large MySQL dataset from InnoDB to RocksDB to reduce footprint. His blog also has other thoughts on MyRocks and InnoDB.
Of course, checkout the new site for all things MyRocks! It has a getting started guide amongst other things.
Proxies: MariaDB MaxScale, ProxySQL
With MariaDB MaxScale 2.0 being relicensed under the Business Source License (from GPLv2), almost immediately there was a GPLScale fork; however I think the more interesting/sustainable fork comes in the form of AirBnB MaxScale (GPLv2 licensed). You can read more about it at their introductory post, Unlocking Horizontal Scalability in Our Web Serving Tier.
ProxySQL has a new webpage, a pretty active mailing list, and its the GPLv2 solution by DBAs for DBAs.
Vitess
Vitess 2.0 has been out for a bit, and a good guide is the talk at Percona Live Amsterdam 2016, Launching Vitess: How to run YouTube’s MySQL sharding engine. It is still insanely easy to get going (if you have a credit card), at their vitess.io site.
Posted on 8/4/2016, 6:07 pm, by Colin Charles, under
MariaDB,
MySQL.
While being on the committee for the FOSDEM MySQL & friends devroom, I didn’t speak at that devroom (instead I spoke at the distributions devroom). But when I had time to pop in, I did take some notes on sessions that were interesting to me, so here are the notes. I really did enjoy Yoshinori Matsunobu’s session (out of the devroom) on RocksDB and MyRocks and I highly recommend you to watch the video as the notes can’t be very complete without the great explanation available in the slide deck. Anyway there are videos from the MySQL and friends devroom.
MySQL & Friends Devroom
MySQL Group Replication or how good theory gets into better practice – Tiago Jorge
- Multi-master update everywhere with built-in automatic distributed recovery, conflict detection and group membership
- Group replication added 3
PERFORMANCE_SCHEMA tables
- If a server leaves the group, the others will be automatically informed (either via a crash or if you execute
STOP GROUP REPLICATION)
- Cloud friendly, and it is self-healing. Integrated with server core via a well-defined API. GTIDs, row-based replication,
PERFORMANCE_SCHEMA. Works with MySQL Router as well.
- Multi-master update everywhere. Conflicts will be detected and dealt with, via the first committer wins rule. Any 2 transactions on different servers can write to the same tuple.
- labs.mysql.com / mysqlhighavailability.com
- Q: When a node leaves a group, will it still accept writes? A: If you leave voluntarily, it can still accept writes as a regular MySQL server (this needs to be checked)
- Online DDL is not supported
- Checkout the video
ANALYZE for statements – Sergei Petrunia
- a lot like EXPLAIN ANALYZE (in PostgreSQL) or PLAN_STATISTICS (in Oracle)
- Looks like explain output with execution statistics
- slides and video
Preparse Query Rewrite Plugins – Sveta Smirnova / Martin Hansson
- martin.hansson@oracle.com
- Query rewwriting with a proxy might be too complex, so they thought of doing it inside the server. There is a pre-parse (string-to-string) and a post-parse (parse tree) API. Pre-parse: low overhead, but no structure. Post-parse: retains structure, but requires re-parsing (no destructive editing), need to traverse parse tree and will only work on select statements
- Query rewrite API builds on top of teh Audit API, and then you’ve got the pre-parse/post-parse APIs on the top that call out to the plugins
- video
Fedora by the Numbers – Remy DeCausemaker
MyRocks: RocksDB Storage Engine for MySQL (LSM Databases at Facebook) – Yoshinori Matsunobu
- SSD/Flash is getting affordable but MLC Flash is still expensive. HDD has large capacity but limited IOPS (reducing rw IOPS is very important and reducing write is harder). SSD/Flash has great read iops but limited space and write endurance (reducing space here is higher priority)
- Punch hole compression in 5.7, it is aligned to the sector size of your device. Flash device is basically 4KB. Not 512 bytes. So you’re basically wasting a lot of space and the compression is inefficient
- LSM tends to have a read penalty compared to B-Tree, like InnoDB. So a good way to reduce the read penalty is to use a Bloom Filter (check key may exist or not without reading data, and skipping read i/o if it definitely does not exist)
- Another penalty is for delete. It puts them into tombstones. So there is the workaround called SingleDelete.
- LSMs are ideal for write heavy applications
- Similar features as InnoDB, transactions: atomicity, MVCC/non-locking consistent read, read committed repeatable read (PostgreSQL-style), Crash safe slave and master. It also has online backup (logical backup by mysqldump and binary backup by myrocks_hotbackup).
- Much smaller space and write amplification compared to InnoDB
- Reverse order index (Reverse Column Family). SingleDelete. Prefix bloom filter. Mem-comparable keys when using case sensitive collations. Optimizer statistics for diving into pages.
- RocksDB is great for scanning forward but ORDER BY DESC queries are slow, hence they use reverse column families to make descending scan a lot faster
- watch the video
