… actually a form of Eventual Consistency where the client is forced to correct the problem before it can commit. It is NOT…); UPDATE groups SET last_joined=NOW(), last_user_id=100 WHERE id=1; COMMIT; How often might multiple users join the same group… count = $last_count where achievement = ‘killed_troll’”; } change your schema In Example 2, above, how above moving the ‘joined‘ column to the…
Post: Benchmarking Percona Server TokuDB vs InnoDB
May 7, 2013 By 32 Comments
…is better) and we start with empty tables. Now, before looking at the graph, please do not jump … I understand that my PRIMARY KEY (`hid`,`mid`,`id`) where `id` is sequential, and `hid`,`mid` is low … max_heap_table_size = 64M sort_buffer_size = 4M join_buffer_size = 4M thread_cache_size = 1000 query_…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
…, and the OS installed is Centos 6.2 Table Structure Before moving on, let’s take a look at the structure… can see where Hash Joins work best and where they don’t. First of all Hash joins only work for equijoins. Hash join work best when you are joining very big tables with no WHERE clause, or a WHERE clause…
Post: Enum Fields VS Varchar VS Int + Joined table: What is Faster?
January 24, 2008 By 30 Comments
… had available for tests) Two important notes about this table before we get to results – this is rather small table which… INT + join: select SQL_NO_CACHE c.city from cities_join c JOIN states s ON (s.id = c.state_id) WHERE s.name… no join: mysql> EXPLAIN select SQL_NO_CACHE c.city from cities_join c JOIN states s ON (s.id = c.state_id) WHERE…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 4 Comments
… told before MySQL has only supported one join algorithm and that is Nested Loop Join. MariaDB has introduced a new join algorithm Hash Join. This join…_shippriority from customer, orders, lineitem FORCE INDEX (i_l_orderkey) where c_mktsegment = ‘AUTOMOBILE’ and c_custkey = o_custkey and l…
Post: Using delayed JOIN to optimize count(*) and LIMIT queries
April 6, 2007 By 22 Comments
… way MySQL generates full rows while executing queries with limit before throwing them away which makes queries with high offset values… fact where i select count(*) from fact left join dim on val=id where i select i,pad from fact left join dim on val=id where i select i…
Post: JOIN Performance & Charsets
October 21, 2008 By 2 Comments
We have written before about the importance of using numeric types as keys, but …_id`) AS `COUNT(t1.char_id)` from `test`.`t1` join `test`.`t2` where (`test`.`t1`.`char_id` = convert(`test`.`t2`.`char_id…_id`) AS `COUNT(t1.char_id)` from `test`.`t1` join `test`.`t2` where (`test`.`t2`.`char_id` = `test`.`t1`.`char_id`) 1…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
… min 58.63 sec) mysql> select count(pad) from large where val between 1 and 100; +————+ | count(pad) | +————+ | 314008 | +————+ 1 row… reduce the gap but I doubt it will be closed. Joins Joins are used to compose the complex object which was previously… to avoid it. Joins to smaller tables is OK but you might want to preload them to memory before join so there is…
Post: Thank you for joining us at Percona Live, NYC 2012
October 7, 2012 By 1 Comment
…between MySQL and NoSQL have not seen before Ospero Ltd have been showcasing their solutions…allowing to dramatically increase performance of complicated join queries. MySQL users are always hungry …showing it is not only rotating media where Fractal Trees technology can show significant performance …
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… displayed. OS Wait is not exactly the same as “reservation” – before falling back to complex wait using sync_array Innodb tries… id 100627 localhost root Updating update iz set pad=’a’ where i=1 *** (2) HOLDS THE LOCK(S): RECORD LOCKS space… kernel status could be “waiting in InnoDB queue” or “sleeping before joining InnoDB queue”. Latest one is quite interesting – to avoid too…
