… your hard drive sequential read rate or you would see MySQL becoming CPU bound if IO subsystem is too fast. In… reads are single page (16K reads). In case of non fragmented table you would see Innodb sequential read-ahead kick in which… fragmentation is also the issue. Interesting enough the “cure” for both fragmentation issues is the same – OPTIMIZE TABLE tbl – this command recreates the table…
Post: Working with many files and file system fragmentation
March 18, 2008 By 11 Comments
… to repeat the test with MySQL MyISAM tables and see how bad the difference would be for MySQL but I would expect something… – one could optionally preallocate MyISAM tables in some chunks (say 1MB) so its gets less fragmentation. Though it would be interesting to… approach would generally help. Until we have this feature – reduced fragmentation is one more benefit we get with batching. For example…
Post: Pretty-formatted index fragmentation with xtrabackup
March 15, 2011 By 4 Comments
… InnoDB tables and indexes. This can be useful to examine whether you’d benefit from “defragmenting” your MySQL database with OPTIMIZE TABLE, although… formats the stats output nicely to give an overview of fragmentation. It’s an initial draft, and if you find issues… top of the code listing. The output looks like this: TABLE INDEX TOT_PAGES FREE_PAGES PCT_FULL art.link_out104…
Post: MySQL 5.5 and MySQL 5.6 default variable values differences
February 21, 2013 By 8 Comments
… the values from MySQL 5.5.30 and MySQL 5.6.10 to the different tables and ran the query: mysql [localhost] {msandbox} (test…_THREAD_INSTANCES | 1000 | 224 | | SOCKET | /tmp/mysql_sandbox5530.sock | /tmp/mysql_sandbox5610.sock | | INNODB_FILE_PER_TABLE | OFF | ON | | SYNC_MASTER_INFO | 0… now 64MB instead of 8MB which should help to reduce fragmentation and make file growth more rare event. max_connect_errors…
Post: MySQL Indexing Best Practices: Webinar Questions Followup
August 16, 2012 By 4 Comments
… your inserts and make primary key significantly fragmented. I also would note there are some MySQL optimizer restrictions in how well it… of indexes you can have, which is 64 per table in recent MySQL versions. However it is often too many. Instead of…. Q: how mysql use index for group by? A: If you have Index on the column MySQL can avoid temporary table or filesort…
Post: INFORMATION_SCHEMA tables in the InnoDB pluggable storage engine
May 24, 2008 By Leave a Comment
…tables that show some status information about InnoDB. Here are the tables: mysql> SHOW TABLES FROM INFORMATION_SCHEMA LIKE ‘INNODB%’; +—————————————-+ | Tables…, decompression, memory management, fragmentation etc. Beware that selecting from the tables whose names contain …
Post: Long PRIMARY KEY for Innodb tables
October 3, 2006 By 8 Comments
… did I use this solution compared to others: Innodb Tables – This table is getting much more reads than writes so transactional overhead… dramatically. No recovery worries – checking/repairing large MyISAM tables in case of MySQL/System crash is painful and great to be avoided… happen. Full table scan for this table would also be slow as it is quite fragmented. Table however is not getting any table scans just…
Post: MySQL File System Fragmentation Benchmarks
March 21, 2008 By 28 Comments
…I found: The fragmentation we speak in this article is filesystem fragmentation or internal table fragmentation which affects performance of full table scan. Not … amount of tables and does specified number of inserts going to random tables. I used default MySQL settings for MyISAM (table_cache=…
Post: InnoDB: look after fragmentation
November 5, 2009 By 12 Comments
…problem at first. The table is CREATE TABLE `c` ( `tracker_id` int(…+—————————+ 1 row in set (2 min 8.92 sec) mysql> SHOW STATUS LIKE ‘Innodb_scan_pages%’; +——————————+——-+ | Variable_name…So notes to highlight: InnoDB fragmentation may hurt your query …
Post: MySQL Query Cache
July 27, 2006 By 70 Comments
… great feature called “Query Cache” which is quite helpful for MySQL Performance optimization tasks but there are number of things you… from this table are invalidated at once. Most of them quite likely would not have change their result set but MySQL has… cache on table modifications – if there are a lot of queries being cached this might reduce update speed a bit. Fragmentation over…
