… and then subsequent queries against the temp table fail. Q: Why doesn’t the query optimizer take care the execution decisions? Since they… to the same execution plan. (I know it doesn’t though.) Why don’t you try writing a SQL query optimizer and… you have irregular distribution of matching rows that you’ll get skewed results. For instance, if there’s a gap of…
Post: The small improvements of MySQL 5.6: Duplicate Index Detection
May 31, 2013 By Leave a Comment
…-, but we will get a warning (note severity, to be exact): mysql> ALTER TABLE test ADD INDEX (col2); Query OK, 0 rows…? Let’s see an example. If we execute: mysql> ALTER TABLE test ADD INDEX (col2); Query OK, 0 rows affected (0.34… # Total Indexes 2 By the way, if you want to get more familiar with this and other particularities of the latest…
Post: Choosing a MySQL HA Solution - Post-Webinar Q&A
June 7, 2013 By Leave a Comment
… intact, and then the binary log filters are executed on the intermediate server, thus resulting in less … simply attempt to connect and run a simple query, but it’s always possible to build something …. Q: What kind of replication issues can you get with storage solutions like GlusterFS? A: I have …
Post: High-load problems? Investigate them with 'pt-query-digest'
April 23, 2013 By 2 Comments
… run time data available, but at least you get a nice ranking of queries sorted by the number of times they appear… that by pt-query-digest –type rawlog –report-format profile, to get just the ranking of queries. To my luck, one query stood out… that query (actually the customer removed it altogether, by merging it with another query that ended up having a much better execution plan…
Post: Slow Query Log analyzes tools
September 6, 2006 By 84 Comments
… ? Unfortunately general logs queries before queries are executed (and even parsed) so it can’t contain query execution information such as execution and lock times and… easy to get sample of all queries for some period of time and then get back to logging only very slow queries. Once you…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 20 Comments
…original query execution time. It may be possible, therefore, to refresh an MV based on a query that takes 45 minutes to execute …determine the contents of the view. mysql> select flexviews.get_sql( -> flexviews.get_id(‘demo’,'dashboard_customer_sales’)) -> as ‘SQL’ \G *************************** …
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
… 167 different queries. Following that there are summaries of various data points such as the total query execution time and the average query execution time… is “Get yourself Percona Server, turn on log_slow_verbosity and start using pt-query-digest”, your job of identifying queries producing most…
Post: The new cool MySQL patch has landed! Check your queries performance!
October 31, 2007 By 16 Comments
… is the same as for its predecessor – to get more information about query execution logged into slow log, however the new version is… –log-slow-slave-statements. THE DETAILED INFORMATION ABOUT QUERY EXECUTION Each query can be executed in various ways. For example it may use indexes… by a query as there is more chance for hash collisions. In case InnoDB is not used for the query execution that information…
Post: What time 18446744073709550.000 means
May 17, 2009 By 25 Comments
…-core AMD Opteron systems appeared and I noticed sysbench getting crazy showing query execution time 18446744073709550.000 or like this. Obviously this is…, &tp); … query_execution … end_time = clock_gettime(CLOCK_THREAD_CPUTIME_ID, &tp); total_time = end_time – start_time; How we can get query executed in…
Post: How to Identify Bad Queries in MySQL
January 10, 2011 By 16 Comments
… I’m referring to the timestamp when the query executed, not merely the duration the query executed for, which has been available in MySQL for years. This is necessary for determining whether a group of queries completed in a cluster. One-second granularity (what you get in standard MySQL) might be…
