This blog post is part two in what is now a continuing series on the Star Schema Benchmark. In … I believe the adaptive hash index is improving performance of InnoDB significantly during the hot run, as hash indexes are faster than a… metadata_locks_hash_instances=32 table_open_cache_instances=8 sort_buffer_size=128k read_rnd_buffer_size=8M join_buffer_size…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
… a new join type “Hash Joins” which is an implementation of a Classic Block-based Hash Join Algorithm. In this post we will see what the Hash Join is, how… above that what is actually implemented is the Classic Hash Join. But its known as Block Nested Loop Hash (BNLH) Join in MariaDB. The Classic Hash Join Algorithm consists…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 4 Comments
… is Hash Joins. Hash Join As I have told before MySQL has only supported one join algorithm and that is Nested Loop Join. MariaDB has introduced a new join… what specific types of queries would benefit from Hash Join as compared to Nested Loop Join, but for now it looks like Nested Loop Join is…
Post: MySQL Indexing Best Practices: Webinar Questions Followup
August 16, 2012 By 4 Comments
…is string comparison in MySQL is case insensitive by default while hash comparison will be done case sensitive unless you lowercase string before hashing…is used to join the two tables? A: The question in this case is how MySQL will execute the join… described in presentation. Q: what is the impact on…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… transaction status is reported which is basically what transaction is doing it can …or “sleeping before joining InnoDB queue”. Latest one is quite interesting …hash index is hash index Innodb builds for some pages to speed up row lookup replacing btree search with hash search. This section shows hash…
Post: How well does your table fits in innodb buffer pool ?
December 9, 2010 By 12 Comments
…(hashed = 1) hashed FROM innodb_buffer_pool_pages_index GROUP BY index_id) bp JOIN innodb_sys_indexes ON id = index_id JOIN innodb… table (cnt), how many of them are dirty (dirty), and what is the percentage of index fits in memory (fit_pct) For… stats during warmup to see what is really getting warmed up first as well as how buffer pool is affected by batch jobs…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
… matches to particular index value or range. What is often forgotten about is – depending if workload is cached or not different selectivity might show… MySQL is lack of advanced join methods at this point (the work is on a way) – MySQL can’t do hash join or sort merge join… joins to large tables Joining of large data sets using nested loops is very expensive. Try to avoid it. Joins to smaller tables is OK…
Comment: Join Optimizations in MySQL 5.6 and MariaDB 5.5
June 18, 2012 By 4 Comments
… why there is no support of hash-join or sort-join in MySQL 5.5 . What is problem in using this join algorithm ? I think these is very fast in case of large tables or small main-memory . My Guess : 1) nested loop join can run faster in case of smaller tables. 2) hash join can not support theta join.
Post: High-Performance Click Analysis with MySQL
December 22, 2008 By 13 Comments
… denormalization is important is that nested-loop joins on large data sets are very expensive. If MySQL supported sort-merge or hash joins, you…, impressions int unsigned not null, …. primary key(day, ad, is_blue) ); What can we improve here? Especially assuming that there are indexes…
Post: Using CHAR keys for joins, how much is the overhead ?
June 18, 2007 By 18 Comments
… | 10239901336 | +———————————-+ 1 row in set (1.70 sec) Here is explain if someone curious, it did not… 2 rows in set (0.00 sec) So what about Innodb ? Innodb executed the same query… all numbers with their sha1() hashes which still made eq join to run the same ways…
