maria-discuss team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Nicolas!

On Dec 19, Nicolas Payart wrote:
> Hi list,
> 
> I am using Spider Storage Engine for sharding data and remote access to 
> some innodb tables on 3 different MariaDB 10.0.14 instances.
> 
> It performs quite well in production except that sometimes, some queries 
> (a minority of them fortunately) do not respond and stay indefinitely in 
> "query end" state in processlist.
> 
> What can make a query stay indefinitely in "query end" state?
> Maybe a bug in Spider Storage Engine?
> 
> Any advice is welcome!

I've asked the author of the Spider engine - Kentoku Shiba - and he
thinks that these queries don't stay indefinitely, but are just very
slow. They would be slow because, let me quote

  ... this case needs BKA join for better performance. But current table
  partition feature of official MariaDB does not support MRR well. In
  the other hand, there is a patched version of MariaDB that supports
  MRR well with partition feature. I will contribute this patch to
  official MariaDB.

meanwhile you can try the patched version of MariaDB (as prepared by
Kentoku) with BKA and see if that helps:

  Latest patched version of MariaDB source code
  http://spiderformysql.com/downloads/spider-3.2/mariadb-10.0.13-spider-3.2-vp-1.1-mroonga-4.05h.tgz
  binary for Linux x86_64
  http://spiderformysql.com/downloads/spider-3.2/mariadb-10.0.13-spider-3.2-vp-1.1-mroonga-4.05-linux-x86_64-glibc25h.tgz

Hmm, judging from the name this includes Spider 3.2, Vertical Partitioning
engine 1.1 and Mroonga 4.05h

Regards,
Sergei