… need to scan the full tables and in turn, load that data into and pollute the buffer pool. Note that this can be somewhat mitigated using innodb…mysql/orig_old Make sure that the files are owned by mysql: chown mysql:mysql /var/lib/mysql/orig_old/* For each table, run: ALTER TABLE…
Post: Full table scan vs full index scan performance
November 23, 2012 By 15 Comments
… 2nd worst possible execution plan after a full table scan. If it is obvious that a full table scan is not good for performance, how much… database, and slightly modify the employees tables: mysql> ALTER TABLE employees ADD INDEX idx_first (first_name),ENGINE=InnoDB; And then let’s consider…
Post: Is there room for more MySQL IO Optimization?
January 3, 2013 By 11 Comments
…Innodb_data_reads | 54561 | | Innodb_data_reads | 38277 | | Innodb_data_reads | 25895 | | Innodb_data_reads | 31363 | | Innodb_data_reads | 170816 | | Innodb_data_reads | 207432 | | Innodb…more information MySQL has about data which will be accessed next – in case of full table scan, index scans etc …
Post: The new cool MySQL patch has landed! Check your queries performance!
October 31, 2007 By 16 Comments
…. For example it may use indexes or do a full table scan, or a temporary table may be needed. These are the things that… sorting was done through temporary files. INNODB USAGE The final part are the InnoDB usage statistics. MySQL currently allows you to see many… Full_scan: No Full_join: No Tmp_table: Yes Disk_tmp_table: No # Filesort: Yes Disk_filesort: No Merge_passes: 0 # InnoDB_IO_r_ops: 19 InnoDB…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
… to make full table scans and index scans more efficient. I can’t wait for ability to create physically sorted indexes with Innodb (with index… little known new features in MySQL 5.1 Q15: How frequently does Innodb fuzzy checkpointing is activated HT: InnoDB flushes about 128 dirty…
Post: MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark
March 11, 2013 By 7 Comments
… defaults between MySQL 5.5 and MySQL 5.6 and innodb_old_blocks_time immediately came to mind. The InnoDB plugin introduced innodb_old_blocks… original InnoDB, the LRU was implemented as a classic LRU which is subject to “pollution” by full table scans. In the classic LRU, a full table scan…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
… table has 10000 distinct value, so range 1..100 selects about 1% of the table. The times for full table scan vs range scan by index: mysql… require radom IO if index ranges are scanned. There are also clustered keys in Innodb which combine index access with data access… with in temporary table etc. Prefer full table scans to index accesses – For large data sets full table scans are often faster than range scans and other types…
Post: MySQL File System Fragmentation Benchmarks
March 21, 2008 By 28 Comments
… tables. I used default MySQL settings for MyISAM (table_cache=64) and set innodb_buffer_pool_size=8G innodb_flush_logs_at_trx_commit=2 innodb… innodb_flush_method=O_DIRECT for Innodb. The tables were sized so they are considerably larger than amount of memory in box so full table scan…
Post: Heikki Tuuri answers to Innodb questions, Part II
November 4, 2007 By 13 Comments
… a hi amount of concurrent writes to about 6 tables, what version of Innodb/MySQL would you recommend? I’ve been staying at… brands. Q37: We have a fairly large Innodb table (150GB) that is showing poor performance for full table scans. using O_DIRECT, we are seeing… InnoDB should have placed the rows in contiguous blocks of 64 pages == 1 MB. Then a full table scan would be fast. Maybe the table…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… id 1150142816 fetching rows, thread declared inside InnoDB 166 mysql tables in use 1, locked 0 MySQL thread id 8078, query id 728898 localhost… id 1147980128 fetching rows, thread declared inside InnoDB 114 mysql tables in use 1, locked 0 MySQL thread id 8077, query id 728897 localhost… random IO these should be 16K – page size, for full table scan or index scan read-ahead may be performed which can increase average…
