… select a Primary Component, we have then a split-brain condition. In our …in set (0.00 sec) percona2 mysql> insert into percona values (0,’percona2′,’daniel’); Query OK, 1 row affected (0.02 sec) percona2 mysql> select…Member 0 (percona1) synced with group. If the communication fails between node1 …
Post: Using any general purpose computer as a special purpose SIMD computer
May 16, 2011 By 5 Comments
… each input asynchronously, if you like. Right…query with BETWEEN 1 and 6 added to the where clause. This creates boundary conditions for our query…mysql> select min(id),max(id) from words; +———+———+ | min(id) | max(id) | +———+———+ | 1 | 3088896 | +———+———+ 1 row in…
Post: Using Flexviews - part two, change data capture
March 25, 2011 By 26 Comments
…triggers can not, under normal conditions, detect the commit order ….php setup starting setup completed If the setup detects any …stores it progress in a metadata table: $ mysql -e ‘select * from flexviews.binlog_consumer_status\G…in a second transaction: mysql> delete from test.demo where c1=1; Query…
Post: Computing 95 percentile in MySQL
November 28, 2008 By 5 Comments
… and get your logs in the table, so how to get the data if MySQL only provides you the avg: mysql> select count(*),avg(wtime… time we concerned about simply by running following order-by queries: mysql> select wtime from performance_log_081128 where page_type=’search’ order… bad in given conditions can be much worse problems. You do not want your best client to suffer for example, even if he…
Post: Tools and Techniques for Index Design Webinar Questions Followup
October 4, 2012 By 5 Comments
…of MySQL. Q: How do the upcoming changes in MySQL 5…condition pushdown. Q: Is it always the case that no second-star index exists for a query…in the predicate, add columns to avoid sorting per query, and add further columns to cover the select… quicker to search. If your query has predicates that allow…
Post: MySQL Backup tools used by Percona Remote DBA for MySQL
March 13, 2013 By 8 Comments
…’s strong points given the conditions. Percona XtraBackup for MySQL for binary backups. Strong…data in a future blog post. Tips/Tricks: run with –kill-long-queries … script use_https = True, especially if your data is not encrypted … WITH READ LOCK”. Namely when a select is blocking the flush from …
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
…query_cache_size=0 query_cache_type=0 optimizer_switch=’index_condition…in the IO bound workload. In this test Hash join is not ideal because you have a highly selective…in query time. The reduction in query time for IO bound workload is 1266x times when compared to MySQL… are enabled. If join_cache_…
Post: A workaround for the performance problems of TEMPTABLE views
May 19, 2010 By 7 Comments
…select c1, c2 from t2; Query OK, 0 rows affected (0.11 sec) If we then write a SQL query…an aggregation query: mysql> create algorithm=MERGE view v2 as select c1, count(*) from v1 group by c1; Query OK… view in a way which provides a different means of providing filter conditions to the query. Lets …
Post: Checking for a live database connection considered harmful
May 5, 2010 By 38 Comments
… Work This code doesn’t work because of a race condition. If the connection is alive when checked, there’s no guarantee… at the MySQL protocol level, which will increment Com_admin_commands in SHOW GLOBAL STATUS, or a trivial query such as ‘SELECT 1′ which is usually harder to diagnose. This has a very high cost in many applications…
Post: MySQL 6.0 vs 5.1 in TPC-H queries
March 25, 2008 By 17 Comments
…in next posts), but I want to write about is queries that execute slower in new MySQL 6.0 version. Query is pretty simple SELECT…Index condition‘, what I was able to find is Baron’s bug with no mention in MySQL 6….is that MySQL is wrong choosing index scan here. If we try to execute query with IGNORE …
