… + 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 for sbtest_r10 * much less for other rollup tables
Post: Learning about MySQL Table Fragmentation
May 1, 2008 By 20 Comments
… table is not logically fragmented and Innodb is reading data in large blocks – this can happen in case Innodb table file is itself fragmented… 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: MySQL File System Fragmentation Benchmarks
March 21, 2008 By 28 Comments
… 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 affects performance of full table scan. Not all…
Post: InnoDB: look after fragmentation
November 5, 2009 By 12 Comments
… on. So let me introduce problem at first. The table is CREATE TABLE `c` ( `tracker_id` int(10) unsigned NOT NULL, `username… dump in primary key order. So notes to highlight: InnoDB fragmentation may hurt your query significantly, especially when data is not… by secondary key To check if you query affected by fragmentation you can use Innodb_scan_pages_contiguous ; Innodb_scan_pages…
Post: Working with many files and file system fragmentation
March 18, 2008 By 11 Comments
… like it does not do very good job preventing file fragmentation for large amount of growing files. It would be interesting… – 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: Quickly preloading Innodb tables in the buffer pool
May 1, 2008 By 9 Comments
…=0 This works relatively well (though can be slow for fragmented tables) but it does not preload indexes in memory neither it… scan Clustered key Anyway. Now, say you have bunch of tables having few indexes – should you run multiple queries in parallel… best preload speed ? It depends – depending on key/clustered key fragmentation it may be faster to run queries one by one…
Post: Pretty-formatted index fragmentation with xtrabackup
March 15, 2011 By 4 Comments
… Perl script) has support for printing out stats on InnoDB tables and indexes. This can be useful to examine whether you’d benefit from “defragmenting” your MySQL database with OPTIMIZE TABLE, although I have not determined firm guidelines for when that… formats the stats output nicely to give an overview of fragmentation. It’s an initial draft, and if you find issues…
Post: INFORMATION_SCHEMA tables in the InnoDB pluggable storage engine
May 24, 2008 By Leave a Comment
… | +—————————————-+ The _CMP tables show statistics about compression; they contain a lot of useful information about compression, decompression, memory management, fragmentation etc. Beware that selecting from the tables whose names contain RESET has a side…
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…, saving IO dramatically. No recovery worries – checking/repairing large MyISAM tables in case of MySQL/System crash is painful and great… 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…
Comment: 5.0.83-build17 Percona binaries
August 6, 2009 By 19 Comments
… with filepertable. Especially if you find your tables fragment a lot. innodb_file_per_table=1 I’m sure other people can chime… set constituting 161,000,000 data rows (details of the table mix was stated above) Obiously this is just my own…
