… for a great performance report. Not sure I understand why InnoDB used 210 GB for 234M rows when loaded in PK… + 234M * (12 + 7) * 1.5 for fragmented secondary index + 234M * (12 + 20) * 1.5 for fragmented sbtest_r10 I assume: * 20 bytes… * fragmented pages are 2/3 full So my guess is: * 50G for PK index * 6G for secondary index on base table * 11G…
Post: Learning about MySQL Table Fragmentation
May 1, 2008 By 20 Comments
… SHOW INNODB STATUS output. It was around 20KB which means most reads are single page (16K reads). In case of non fragmented table you would see Innodb sequential read-ahead kick in which does reads in… if table is not logically fragmented and Innodb is reading data in large blocks – this can happen in case Innodb table file is itself fragmented. To…
Post: InnoDB: look after fragmentation
November 5, 2009 By 12 Comments
…_id`,`username`,`time_id`), KEY `block_id` (`block_id`) ) ENGINE=InnoDB Table has 11864696 rows and takes Data_length: 698,351,616…: InnoDB fragmentation may hurt your query significantly, especially when data is not in buffer_pool and execution goes to read from disk Fragmentation… To check if you query affected by fragmentation you can use Innodb_scan_pages_contiguous ; Innodb_scan_pages_jumpy statistics in 5.0…
Post: MySQL File System Fragmentation Benchmarks
March 21, 2008 By 28 Comments
… and Innodb tables on ext3 filesystem. Here is what I found: The fragmentation we speak in this article is filesystem fragmentation or internal table fragmentation which… – Concurrent growth of many tables causes data fragmentation and affects table scan performance nadly – MyISAM suffers worse than Innodb – Innodb extent allocation works (perhaps would…
Post: Quickly preloading Innodb tables in the buffer pool
May 1, 2008 By 9 Comments
… Innodb tables. Though I thought this topic would benefit from a bit more information. But lest first start with feature request for Innodb… native support. It would be great if Innodb would implement command to preload table to Innodb buffer pool, which would simply go through…=0 This works relatively well (though can be slow for fragmented tables) but it does not preload indexes in memory neither it…
Post: Long PRIMARY KEY for Innodb tables
October 3, 2006 By 8 Comments
…`,`thumb_width`,`thumb_height`) ) ENGINE=InnoDB; Why did I use this solution compared to others: Innodb Tables – This table is getting much more reads… 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: Improved InnoDB fast index creation
November 6, 2011 By 4 Comments
… thing that is worth mentioning is fragmentation. Fast index creation results in much less fragmented indexes because records are inserted… TABLE STATUS versus 265 MB index size with the optimization disabled. OPTIMIZE TABLE OPTIMIZE TABLE is mapped to ALTER TABLE … ENGINE=InnoDB for InnoDB tables …
Post: Heikki Tuuri answers to Innodb questions, Part II
November 4, 2007 By 13 Comments
… run to show any table / index fragmentation, without having to run the OPTIMIZE? HT: Since OPTIMIZE rebuilds the whole table, it may last… pages == 1 MB. Then a full table scan would be fast. Maybe the table has become fragmented? Or maybe you have not inserted… not showed up in “show innodb statusâ€. select * from table where id=5 show innodb status: Hash table size 10624987, used cells 1…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
…. The first 32 pages of a segment are allocated from ‘fragment extents’ where any individual page can be allocated to whatever… single extent. For big tables, a secondary index reserves different extents from the clustered index. Q4: Does Innodb ever merges sequential pages… workloads. Q7: Does Innodb has any protection from pages being overwritten in buffer pool by large full table scan HT: No PZ…
Post: Innodb Double Write
August 4, 2006 By 24 Comments
… very interesting techniques Innodb uses is technique called “doublewrite” It means Innodb will write data twice when it performs table space writes – writes… just between their execution. Reasons for splitting could be file fragmentation – most file systems use 4K block sizes by default so…
