… features in the MEMORY storage engine (also known as HEAP) in MySQL has been one of the long-standing limitations caused by… the community to remove this limitation. In 2008 Igor Chernyshev of eBay implemented true-VARCHAR support for MEMORY tables for MySQL 5… course, if you have a performance-critical application depending on MEMORY tables, they are no replacement for application-specific tests. We…
Post: MySQL Server Memory Usage
May 17, 2006 By 21 Comments
… memory needed for OS, File Cache and other applications. For 32bit envinronment you also should keep 32bit limits into account and probably limit… of memory Prepared statements and Cursors. Single connection may have many prepared statements and cursors. Their number finally can be limited but each of them still can have very large memory consumption Innodb Table Cache. Innodb…
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 5 Comments
… are allocated (and how much memory they use). Memory Tables MEMORY tables can take memory. There are implicit MEMORY tables which are allocated for query…_heap_table_size variable which allows you to limit size of MEMORY tables (the limit applies both to implicit and explicit ones) but… global memory allocation and will result in increased memory allocation until server is restarted. I would suspect memory leak when you see memory usage…
Post: PHP Large result sets and summary tables.
July 6, 2007 By 8 Comments
… the process memory. Not good if there are over 50 millions of rows. Note this limit is not controlled by memory_limit PHP config variable because that only controls memory which passes via PHP memory management which does… all result set in memory but instead streams it from the server, fetching in blocks. There are some limits as you can…
Post: MySQL-Memcached or NOSQL Tokyo Tyrant - part 1
October 15, 2009 By 16 Comments
…, fast, and just works. When your dataset exceeds your memory limitations or the database can simply not keep up any more… simple, fast, and just works. When your dataset exceeds your memory limitations or the database can simply not keep up any more… won’t… and yet others require lots and lots of memory allocated to memcached to be successful. This application selects a…
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
… is example: mysql> explain select * from lt limit 10; +—-+————-+——-+——-+—————+———+———+——+——+————-+ | id | select_type | table | type | possible_keys |… example BLOB fields can’t work with in memory temporary table. The other thing – since MySQL…
Post: Predicting Performance improvements from memory increase
August 7, 2008 By 6 Comments
… working set of say 30GB with uniform data access raising memory from 16GB to 32GB can improve performance order of magnitude… to see limited gains – if your working set already fits in 16GB you may not see any significant gains upgrading memory to… typically do not expect to gain much by increasing the memory. This however have to be watched carefully. Performance does not…
Post: InnoDB Flushing: a lot of memory and slow disk
March 31, 2011 By 57 Comments
… nowadays, for example Cisco UCS C250), your database fits into memory, and your write rate is significant, then the slow disk…). This comes from the fact that MySQL performs changes in memory at a faster rate than it can write to disks… with changes in memory, we need to have a throttling mechanism that will limit the rate of changes in memory. Optimize the flushing…
Post: MySQL Limitations Part 4: One thread per connection
October 27, 2010 By 14 Comments
… this way; some have multiple processes that communicate through shared memory or other means. It’s cheap to create a connection… server. That increases the overhead from thread scheduling, and potentially memory usage as well. I feel like I’m forgetting some… and relies on the binary log, which are two major limitations. And it has subqueries, which are a core, fundamental part…
Post: Profiling MySQL Memory Usage With Valgrind Massif
January 9, 2013 By 3 Comments
… using too much memory overall. Or again, maybe you noticed mysqld’s memory profile slowly growing overtime, indicating a possible memory bug. Whatever… complaining quickly. If you self compile, and those Valgrind-internal limits are still too small, you can easily change them before… execute whatever steps you think are necessary to increase memory usage/trigger the memory problem. You could also just leave the server…
