The statement that “COUNT(*) with InnoDB is slow without a WHERE clause because InnoDB doesn’t cache the row count” only tells part of the story. No, it doesn’t cache the row count. Wish… to InnoDB as well as MyISAM. But there is more to the story. It is easy for MyISAM to maintain the count…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
…innodb_file_per_table=1 innodb_file_format=barracuda innodb_log_file_size=512M innodb_log_files_in_group=2 innodb…is as follows: SELECT s_nationkey, l_shipmode, count(*) FROM supplier INNER JOIN lineitem ON s_suppkey =…lineitem. Hence the reason why hash join is slow in this case, because we have to …
Post: MySQL Binaries Percona build10
December 11, 2008 By 12 Comments
…runtime. Next variables were added: | slow_query_log | ON | | slow_query_log_file | /var/lib/mysql/slow_query.log | for compatibility with …of InnoDB internal hash table memories in SHOW INNODB STATUS | 1.0 | Percona | GPL | | | innodb_io_pattern.patch | Information schema table of InnoDB IO counts…
Post: The new cool MySQL patch has landed! Check your queries performance!
October 31, 2007 By 16 Comments
… InnoDB is not used for the query execution that information is written into the log instead the above statistics. The full slow log entry for a query using InnoDB can look like this: # User@Host: macko… Disk_filesort: No Merge_passes: 0 # No InnoDB statistics available for this query SELECT COUNT(1) FROM t2; Important note: Although the…
Post: Are you designing IO bound or CPU bound application ?
December 20, 2006 By 10 Comments
… the most is there a lot of rows are analyzed – count queries, group by, order by without indexes, search queries etc… most loyal users with slow page load times. So for IO bound applications you will need to add counts for all messages… bound applications Clustering (data locality) also becomes very important – if Innodb tables are used having simply auto_increment id on messages…
Comment: Four ways to optimize paginated displays
October 3, 2008 By 27 Comments
… paging to my website. First attempt used SQL_COUNT_FOUND_ROWS everywhere. This, unfortunately, slowed things down considerably. My solution that works…, count, lastinsert): +——–+———+—————-+ | SERVICE| COUNTER | LASTINSERT | |——–|———|—————-| | forum | 10020202| 2008-10-03…. | | users | 10002| 2008-09-13…. | (I use InnoDB so getting count(*) is too slow…
Post: Figuring out what limits MySQL Replication
March 7, 2007 By Leave a Comment
…based on slow query log, happily the server was running MySQL with slow query…more hours because of the time Innodb takes to open tables first time …, 72740 unique Sorting by ‘c’ __ 001 _______________________________________________________________________ Count : 114329 (2%) UPDATE mlp_rating.rating…
Post: To pack or not to pack - MyISAM Key compression
May 13, 2006 By 4 Comments
… to integer keys. Integer keys still best but for Innodb for example difference is not so large. Let us … benchmarks. I’m testing 4 types of queries: select count(*) from t1, t1 t2 where t1.c=t2.c – … are fast and forward scans are. It is however slow to do reverse scan on the string index. It …
Comment: Innodb Performance Optimization Basics
March 28, 2012 By 75 Comments
Hi, I am facing major issues with slow query output. The tables are in InnoDB with MySQL 5 and RHEL 5. Its….cnf|grep innodb innodb_data_home_dir = innodb_data_file_path = ibdata1:10M:autoextend innodb_log_group_home_dir = /usr/local/mysql/data innodb_buffer… innodb_log_file_size = 65M innodb_log_buffer_size = 8M innodb_flush_log_at_trx_commit = 1 innodb_lock_wait_timeout = 50 A count command…
Post: How expensive is a WHERE clause in MySQL?
October 31, 2008 By 17 Comments
… TABLE `t` ( `a` date NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=latin1; insert into t(a)… I repeated the last statement until it got slow enough that I thought I could do…takes: mysql> select sql_no_cache count(*) from t; +———-+ | count(*) | +———-+ | 8388608 | +———-+ 1 row in set (5….
