Tag - Bugs

Interesting MySQL and PostgreSQL Benchmarks

I had found pile of MySQL and PostgreSQL benchmarks on various platforms which I have not seen before. Very interesting reading.
It does not share too much information about how MySQL or PostgreSQL was configured or about queries. Furthermore MySQL and PostgreSQL has a bit different implementations (ie SubQueries avoided for MySQL) so do […]

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Test Drive of Solid

Not so long ago Solid released solidDB for MySQL Beta 3 so I decided now is time to take a bit closer look on new transactional engine for MySQL. While my far goal is the performance and scalability testing before I wanted to look at basic transactional properties such as deadlock detection, select for […]

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Returning to InnoDB scalability

I’m again returning to InnoDB scalability and related bug #15815 as it hurts many users and customers using multi-cpu servers.
Short intro into problem:
On 4-CPU box 1 thread executes full-table scan select query for 8 sec,
but with 4 threads – each thread executes query for 240 sec.
It is very strange as threads use only SELECT […]

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InnoDB thread concurrency

InnoDB has a mechanism to regulate count of threads working inside InnoDB.
innodb_thread_concurrency is variable which set this count, and there are two friendly variables
innodb_thread_sleep_delay and innodb_concurrency_tickets. I’ll try to explain how it works.
MySQL has pluginable architecture which divides work between mysql common code
(parser, optimizer) and storage engine. From storage engine’s point of view it […]

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Group commit and XA

Returning to post Group commit and real fsync I made several experiments:
I ran sysbench update_key benchmarks without —log-bin, with —log-bin, and with —log-bin and —innodb-support-xa=0 (default value is 1). Results (in transactions / sec)

threads
without —log-bin
—log-bin
—log-bin and
—innodb_support-xa=0

1
1218.68
614.94
1010.44

4
2686.36
667.77
1162.60

16
3993.59
666.14
1161.56

64
3630.55
665.18
1151.36

So we can see group commit is not only broken when XA is enabled but also if XA […]

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Innodb Fuzzy checkpointing woes

As you might know Innodb storage engines uses Fuzzy Checkpointing technique as part of it recovery strategy.  It is very nice approach which means database never needs to “stall” to perform total modified pages flush but instead flushing of dirty pages happens gradually in small chunks so database load is very even.
This works great […]

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