… (and I can investigate further), but I believe the adaptive hash index is improving performance of InnoDB significantly during the hot run, as hash indexes are faster than a b-tree index. Also accessing… 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
… 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… a nicely simplified version of the Classic Hash Join algorithm (http://en.wikipedia.org/wiki/Hash_join#Classic_hash_join) which I will quote below for… 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…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 4 Comments
… one join algorithm and that is Nested Loop Join. MariaDB has introduced a new join algorithm Hash Join. This join algorithm only works with equi-joins. Now let me briefly explain how hash join algorithm…
Comment: Join Optimizations in MySQL 5.6 and MariaDB 5.5
June 18, 2012 By 4 Comments
… join algorithm that works well in majority of the cases. However, I think it would be nice to have hash join and sort join algorithms available as well. MySQL 5.6, MariaDB 5.3 and MariaDB 5.5 support Hash Joins. You can check out my post on Hash Joins here: http://www.mysqlperformanceblog.com/2012/05/31/a-case-for-mariadbs-hash-joins/
Comment: Join Optimizations in MySQL 5.6 and MariaDB 5.5
June 18, 2012 By 4 Comments
… is no support of hash-join or sort-join in MySQL 5.5 . What is problem in using this join algorithm ? I think these… 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: Join performance of MyISAM and Innodb
May 29, 2006 By 6 Comments
… primary key joins are very fast as data is clustered together with index and generally highly optimized Innodb builds hash indexes which… up lookup by indexes by passing BTREE index and using hash, which is faster MyISAM does compression for character keys which… MyISAM still a bit better by primary key join than for secondary key join. I guess because it knows for sure there…
Comment: MySQL Limitations Part 3: Subqueries
February 27, 2013 By 21 Comments
I agree with Tobi that ‘hash join‘ / ‘hash aggregate’ / ‘hash join hints’ are one of the most-wanted features in MySQL.
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
… system. To get an even distribution, the test data was hashed over the values in the date_id column. There will…. This frees disk to use on-disk temporary storage for hash joins and other background operations. This will have a direct impact… innodb-use-sys-stats-table innodb-write-io-threads=4 join-buffer-size=16M key-buffer-size=64M local-infile=on…
Post: Using CHAR keys for joins, how much is the overhead ?
June 18, 2007 By 18 Comments
… so I replaced all numbers with their sha1() hashes which still made eq join to run the same ways but gave me… I read these results ? CHAR keys are indeed slower for joins compared to integer keys Performance degradation can range from few… Tables may suffer significantly if key compression is not disabled Joining on Shorter CHAR keys is significantly faster than Long keys…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
… reduce the gap but I doubt it will be closed. Joins Joins are used to compose the complex object which was previously… of advanced join methods at this point (the work is on a way) – MySQL can’t do hash join or sort merge join – it… less full table scan may be faster. Avoid joins to large tables Joining of large data sets using nested loops is very…
