… number of rows returned. What I would like to see (for example as another slow query log record) is the number of rows which MySQL used to generate result set. Comparing this number with number of rows query actually accessed we can… that easy to implement it in the general sense as you can’t always track the future of individual row. Queries with…
Post: Using Flexviews - part two, change data capture
March 25, 2011 By 11 Comments
… expensive. A change data capture tool can be used to implement an efficient way of refreshing them. What is Change Data…=row to process SBR changes from a MySQL master. I’ll talk more about that in another blog post. FlexCDC does not implement…. This is generally only useful if you have a small number of tables, and you want to track changes on all…
Post: Dynamic row format for MEMORY tables
September 6, 2011 By 3 Comments
… limitation. In 2008 Igor Chernyshev of eBay implemented true-VARCHAR support for MEMORY tables for MySQL 5.0. Although this patch did… for both row formats. (Speaking very strictly, the VM Peak value is not comparable due to slightly different number of rows inserted). In the second test we check if the dynamic row format delivers the memory…
Post: MySQL: Data Storage or Data Processing
November 18, 2007 By 9 Comments
…case however the cache (ie memcache) is often implemented to offload MySQL. When it comes to large scale data … query has to analyze 10.000.000 of rows you’re busted – it simply will take too … so serious data crunches – could be, however the number of such applications would likely grow in the future…
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 63 Comments
…MySQL Query Cache so it once again is appealing to improve performance for MySQL Applications ? Make it Lockless Can we re-implement MySQL…. Many applications in MySQL have very large number of queries doing updates …rows used from query syntax may be hard. Query Cache Storage Engines MySQL …
Post: Using UNION to implement loose index scan in MySQL
August 10, 2006 By 15 Comments
… NULL | 3 | Using where | +—-+————-+——–+——-+—————+——+———+——+——+————-+ 1 row in set (0.00 sec) Note number of rows has decreased from 90556 to… range which covers 5 rows is hundreds of times slower than single row ? If MySQL Optimizer would handle…
Post: MVCC: Transaction IDs, Log Sequence numbers and Snapshots
December 19, 2007 By 3 Comments
MySQL Storage Engines implementing Multi Version Concurrency Control have …transaction/query, however MVCC is usually implemented without having something like snapshot number. Indeed if you look at…running transactions (not committed) is memorized. For each row more than one version can be stored, …
Post: MySQL Users Conference - Innodb
May 9, 2007 By 6 Comments
… cases. Now In MySQL 5.1+ it is also possible to fix this problem for cases when number of rows in auto-increment…” while many of them come from MySQL limits at the time when Innodb was first implemented. Many other transactional Storage Engines do not have the problems because they target at least MySQL 5.1 with row level…
Post: The case for getting rid of duplicate “sets”
May 17, 2011 By 2 Comments
… database was first implemented, write-ahead-logging and other technologies did not exist. This made it difficult to implement the database in… say I have a table of numbers, and I want to sum them all up: mysql> show create table ex1; +——-+—————————————————————————————————–+ | Table | Create… | +—–+——————–+ 4 rows in set (39.82 sec) We can also check to see if any two numbers sum to zero: mysql> select a…
Post: Talking MySQL to Sphinx
April 19, 2009 By 4 Comments
… take over execution after parsing, Sphinx MySQL support has nothing to do with MySQL – it is implementation of the wire protocol from scratch… if you ask but rather only number of rows it needs to reach the LIMIT Sphinx mysql> select forum_id as f from… doe not have native Sphinx API implemented – everyone seems to be able to talk to MySQL these days. Now on performance – for…
