could you explain why the tokudb engine is an advantage?
The main point of TokuDB is not writing everything to the disk thanks to the buffers, and with the very efficient compression, more data fits in the memory and saves the space for big-data applications. ( please someone correct me if I´m wrong)
In our tests TokuDB was vital for our startup. With it, we can use cheap dedicated servers and our performance is amazing. We tried PostgreSQL, MongoDB 3.0 and MySQL 5.7 and they can´t fit our data in a 2TB disk or were slow in our tests.
Not ideal, but simple and valid enough.
Where TokuDB gets its speed boost is by delaying the random reads associated with updating the indexing structure (the Fractal Tree). The buffers are written to disk on checkpoint, but because they're buffers, the potentially random writes are localized to a smaller number of nodes high in the tree, which minimizes the number of disk seeks required. Since sequential I/O is cheaper than random, the sequential writes to the write-ahead log are very fast, so even in very strict durability configurations, TokuDB can easily outperform databases which use random writes to update the indexing structures, such as the B-trees used by InnoDB and most other RDBMSes.
More details here: https://www.percona.com/blog/2011/09/22/write-optimization-m...
http://highscalability.com/blog/2014/8/6/tokutek-white-paper...
Quote:"The idea behind FT(fractal Trees) indexes is to maintain a B tree in which each internal node of the tree contains a buffer. When a data record is inserted into the tree, instead of traversing the entire tree the way a B tree would, we simply insert the Eventually the root buffer will fill up with new data records. At that point the FT index copies the inserted records down a level of the tree. Eventually the newly inserted records will reach the leaves, at which point they are simply stored in a leaf node as a B tree would store them. The data records descending through the buffers of the tree can be thought of as messages that say “insert this record”. FT indexes can use other kinds of messages, such as messages that delete a record, or messages that update a record."
some other links:
http://web.archive.org/web/20150414215556/http://www.tokutek...
http://assets.en.oreilly.com/1/event/36/How%20TokuDB%20Fract...
An interesting new development is http://getkudu.io/ which applies some ideas common with Fractal Trees and other write-optimized data structures (like LSM-trees) to column stores.
At Tokutek, we had some designs for how to implement column store-like data models on Fractal Trees (we called them "matrix stores" because they had some of the benefits of both row stores and column stores), but we didn't get around to implementing them.
I am pretty sure the only other engines that support online DDL is Sybase and DB2.
Online DDL generally means lock free DDL operations.
Not even Oracle, MSSQL, or Postgresql do online DDL. But at least they have transactional DDL, even if it isn't entirely lock-free all the time.
Compared to InnoDB/XtraDB; TokuDB lacks foreign key support, because this was worked into InnoDB years ago because the MySQL server layer doesn't support any kind of constraints. I am hoping for MariaDB to start implementing more modern SQL features which would this be available in supported storage engines.
(The hot path was a single well-optimised query that retrieved all content for the page. The query didn't need to change.)
As it stands now, this content is now being handled by a single (and quite unremarkable) MariaDB slave and assembled on-the-fly like any other web page.
For anyone dealing with gigabytes of text content, I highly recommend giving it a go. You don't even need to screw with your master, just change the table type on the slave.
Fractal tree indexes[1]... Dude!