…phone, n_name, c_address, c_comment order by revenue desc LIMIT 20; In-memory workload Now let’s …not in MySQL 5.6, is that because of a bug in MySQL 5.6 code? As MRR was used in both MySQL … correct query execution plan is not used, there is no difference in query times between MySQL 5.5 and MySQL 5….
Comment: Joining many tables in MySQL - optimizer_search_depth
April 23, 2012 By 5 Comments
… above comment was written long time ago, when I was just hired at MySQL. The assumptions about what are typical MySQL may have… MySQL‘s join optimizer is N!. The goal of this choice was to provide a conservative limit that guarantees that any query… with the change to plan pruning in MySQL 5.6. Ideally, the server should analyze the query and should determine the search depth…
Post: Introducing new type of benchmark
February 25, 2012 By 16 Comments
…the throughput (transactions per second in sysbench; NewOrder transactions Per Minute in tpcc-mysql). However, like Mark Callaghan mentioned in comments, response time is way…response time of queries that handle user load ? The same for mysqldump, how does it affect short user queries ? In fact I …
Post: Should we give a MySQL Query Cache a second chance ?
April 10, 2011 By 63 Comments
…same query typed in by different developers. Supporting different comments is especially important as many application put extra information in the comments … queries, for which tracking exact rows used from query syntax may be hard. Query Cache Storage Engines MySQL Query Cache now stores queries in…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
…being confused, thinking MySQL Query Cache is the same as Oracle Query Cache – meaning cache where execution plans are cached. MySQL Query Cache is …place dynamic comments in the query, have extra space or use different case – these would be different queries for query cache. Only SELECT queries are …
Post: How to Identify Bad Queries in MySQL
January 10, 2011 By 16 Comments
…. (Post comments if I’m wrong.) Here is my definition: Queries are bad either singly (an individual query is bad) or in aggregate (a… 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…
Post: MySQL Query Cache WhiteSpace and comments
March 20, 2008 By 9 Comments
Commenting on my previous post on MySQL Query Cache Gerry pokes me as I’m all wrong and both comments and whitespace are fixed in MySQL… So in the nutshell you should be more free now in regards of some SELECT queries not cached because of whitespace or comments in front of them. Though you still need to have queries exactly the same including comments to make them cached by query cache…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
…InnoDB DEFAULT CHARSET=latin1 COMMENT=’Contains all avaialble data from 1988 to 2010′; mysql> use ontime1; Database changed mysql> show table status like…run_query script will run one more more semicolon terminated SQL statements. The queries for the benchmark are in ~ec2-user/shard-query/queries.sql…
Post: A micro-benchmark of stored routines in MySQL
August 16, 2009 By 7 Comments
… execution plan. You should never use IN() subqueries the way I do, at least not in MySQL 5.1 and earlier. I loaded the World sample database and cooked up this query: select sql_no… subquery badly in the first query! (If you think of a better way to compare apples and uhm, apples… please comment). The poorly…
Post: mk-query-digest, query comments and the query cache
…time, mysql query times, etc, and automatically places this information into the Apache environment. It also includes support for “augmenting” SQL queries …executed 1000 times in each iteration of the loop. The queries differ only by comments. In the best case scenario where comments are stripped we…