… same is true for MyISAM which over time will get fragmented rows. Freshly created Innodb table will most likely result in…. Though even in the most fragmented case there is a major difference in primary index scan vs other index scan. The data is… page in order. If you’re doing index scan changes are the same 16K index page will contain 500 pointers causing up…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
… can’t wait for ability to create physically sorted indexes with Innodb (with index built by sort) this is when this should…. The first 32 pages of a segment are allocated from ‘fragment extents’ where any individual page can be allocated to whatever…, and also it can release individual pages from its 32 ‘fragment extent’ pages. PZ: This is the reason why when you…
Post: Quickly preloading Innodb tables in the buffer pool
May 1, 2008 By 9 Comments
… WHERE non_index_col=0 This works relatively well (though can be slow for fragmented tables) but it does not preload indexes in… WHERE index_col like “%0%” for each index. Only one such query per index is enough even if it is multiple column index. To… few indexes – should you run multiple queries in parallel to get best preload speed ? It depends – depending on key/clustered key fragmentation…
Comment: Falcon Storage Engine Design Review
January 12, 2007 By 19 Comments
… the point of fluffing up the index with records? A denser index is a faster index. Clustered indexes are a vestige from the small… the serial log. Other Stuff Rows on disk can be fragmented if they’re too big to fit on a page… around the page cache manager, so the cost of a fragmented record probably isn’t worth worrying about. For real world…
Post: Feature preview: Compact backups in Percona XtraBackup
January 29, 2013 By 11 Comments
…-log –rebuild-indexes /data/backup As a bonus, secondary indexes are created by sorting, that in general gives much less fragmented indexes, so it may result in an additional space saving. In fact this –rebuild-indexes can be used on a full backup, and it will result in rebuilt de-fragmented indexes. I encourage you…
Comment: Working with many files and file system fragmentation
March 18, 2008 By 11 Comments
… are optimized periodically b.big tables that are affected by fragmentation can be arranged as 1 file per filesystem c. recently…) and disk for historical data (less used). Index files are the most prone to fragmentation – since 1 record inserted/updated can trigger updates on several indices. No filesystem is immune to fragmentation unfortunately, the only way to reduce it is to have…
Comment: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
… – is given index (range) currently in memory or will it need to read it from the disk ? How much index is fragmented ? How… not mentioned it in the article but there is IGNORE INDEX() hint to force full table scan. There is no rule… sorts indexes themselves and removers row fragmentation (all for MYISAM tables). It however can’t make row retrieval which is done by index…
Comment: Falcon Storage Engine Design Review
January 12, 2007 By 19 Comments
… row lookup speed. Innodb uses alternative approach with adaptive hash indexes. Two sizes: Right if you say max-size*0.9… not changed by update statement. Thanks for clarification about row fragmentation – so row is not moved to new page if it… not fit to the old one any more but gets fragmented now right ? Regarding real world applications – very significant part of…
Post: Using MyISAM in production
June 17, 2006 By 36 Comments
… may cause total block if there are long selects running. Fragmentation. This is common problem for pretty much all storage engines. It is however also different. MyISAM has in-row fragmentation which means single row may be stored in many pieces… improve performance dramatically in certain cases by avoiding flushing dirty index blocks from key_buffer to disk, but it also comes…
Comment: Using MyISAM in production
June 18, 2006 By 36 Comments
Right. 10 fragments per row are seen in rather rare cases. Mainly if … keyfile length: 4398046510079 Recordlength: 796 table description: Key Start Len Index Type Rec/key Root Blocksize 1 777 4 multip. long… for this table. Some rows however can be fragmented more than others. If you have major fragmentation running OPTIMIZE table will help.
