…. The reason is that when using merge sort, InnoDB has to scan the clustered index only once, even though the actual sorting… default method, because it does not have to do random disk seeks to fetch secondary index pages to the buffer pool. A… PRIMARY KEY defined, because in this case InnoDB picks such an index as the clustered one. References: Peter’s post MySQL bug…
Post: How multiple disks can benefit for single client workload ?
April 26, 2008 By 4 Comments
… will need to fetch clustered index page at least to do it. These reads are issues by Innodb one by one – next… idle. The other seek time optimizations come from the striping – consider 100GB database which is stored on single disk. Assuming it is… from optimizing seeks. You can have shorter seeks but as soon as you have any seeks you will be far from sequential disk access…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
…, a secondary index reserves different extents from the clustered index. Q4: Does Innodb ever merges sequential pages together if they become almost… the full write speed of the disk for throughput. INNODB uses fuzzy checkpointing to commit data to disk. The problem that we’ve…% of the raw disk write speed. Since the commit isn’t perfectly serial it’s having to seek on disk which slows down…
Post: MySQL Blob Compression performance benefits
January 11, 2008 By 17 Comments
… and performance gains, especially for Innodb tables. With Innodb tables BLOB gets its own page (allocated outside of clustered index) if the whole… retrieval unless it is in cache will require an extra disk seek. Also remember each BLOB which does not fit in the… page or set of pages potentially requiring a lot of disk seeks for row retrieval and a lot of space wasted. So…
Comment: InnoDB: look after fragmentation
November 7, 2009 By 12 Comments
Miguel, Indeed Innodb clusters data by primary key. This clustering is however per page. For example in case we would use MyISAM we could get a “disk seek” and IO for each row in worse case scenario – in Innodb it does not happen. The…
