… end up with non-deterministic ordering of transactions as a result. So this brings us back to Callaghan’s law for… SET last_joined=NOW(), last_user_id=100 WHERE id=1; COMMIT; How often might multiple users join the same group? Results In… is 1 retry). This means more waiting, and after the limit is exceeded you will still get the deadlock error. This…
Post: Keynotes, BOFs, and the Community Networking Reception at Percona Live MySQL Conference and Expo
April 15, 2013 By 1 Comment
… Community Networking Reception, I’m pleased to offer a limited number of $5 Expo Only passes. Use discount code…in terms of both functionality and support. As a result of that choice, we are seeing the increasing …of the cloud and big data. If you can join us in Santa Clara for the Percona Live …
Post: Enum Fields VS Varchar VS Int + Joined table: What is Faster?
January 24, 2008 By 30 Comments
…=’Minnesota’ limit 10000,5; Result time(mean): 0.085637 3) Results for INT + join: select SQL_NO_CACHE c.city from cities_join c JOIN states… pass (filesort) is required, which also makes MySQL to store Join result in temporary table to do the sort, all together makes….city, s.name from cities_join c JOIN states s ON (s.id = c.state_id) limit 10000,5; Result time(mean): 0.004170…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
… S and add the resulting join tuples to the output relation Now after the explanation of the hash join lets see how it…’ optimizer_switch=’join_cache_hashed=on’ optimizer_switch=’join_cache_bka=on’ join_cache_level=4 join_buffer_size=32M join_buffer_space_limit=32M Note that MariaDB includes a new variable ‘join…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 100 Comments
… very important to have ORDER BY with LIMIT executed without scanning and sorting full result set, so it is important for it… by column in leading table if you have JOIN with ORDER BY … LIMIT you should try hard to have sorting column(s… results are static it may make sense to precompute results so you can query them for positions. So instead of query with LIMIT…
Post: Using delayed JOIN to optimize count(*) and LIMIT queries
April 6, 2007 By 22 Comments
… to be joined to get query result. If you’re executing count(*) queries for such result sets MySQL will perform the join even if you use LEFT JOIN so… performance you can “Help” MySQL and remove JOIN for count(*) and do JOIN after limiting result set for retrieval queries. Lets look at following…
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
… you statement looks at portion of data with different distribution results can be off by 10-100 times and even more… is join_buffer which reduces number of passes MySQL had to perform and so number of row combinations really examined. LIMIT is… enough to perform sorting or use temporary table with partial result set (partial rows) and than compose full rows by reading…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 4 Comments
… the hash join algorithm here. Now let’s move on to the benchmarks, to see the difference in numbers. Benchmark results For… revenue desc, o_orderdate LIMIT 10; In-memory workload Now let’s see how effective are the join optimizations when the workload…. Note that as mentioned at the start of the benchmark results section, the InnoDB dataset size is ~5G. Now let’s…
Post: Innodb row size limitation
April 7, 2011 By 12 Comments
… compression will work). Something important to note is that the result of the COMPRESS function is always binary, so for example… for the added join complexity. However, if you have too much variable length columns and you can’t limit their size, this… the single BLOB field with COMPRESS/UNCOMPRESS can yield great results. Finally, let me mention that handling of overflow pages involves…
Post: Be careful when joining on CONCAT
October 16, 2007 By 16 Comments
… performance of a rather simple join. It was a join on tb1.vid = CONCAT(‘prefix-’,… the arguments include any binary strings, the result is a binary string. A numeric …tb2.gid = 1337 -> ) ORDER BY tb1.title ASC LIMIT 4\G *************************** 1. row *************************** id: 1 select_type:…
