… ? The reason is its plan benefits from Innodb specific feature – index entries being sorted by primary key for each complete key value. So…` (`a`,`b`) ) ENGINE=InnoDB AUTO_INCREMENT=6029313 DEFAULT CHARSET=latin1 mysql> select * from idxitest where a=100 order by id desc limit… indexes. If you have query plans depending on Innodb ordering of data by primary key inside indexes they can become significantly affected…
Post: Extending Index for Innodb tables can hurt performance in a surprising way
May 22, 2010 By 10 Comments
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
… it more sequential, by having a buffer in between where secondary key tuples are buffered and then sorted by the primary key values… InnoDB contain primary key columns) Buffer each pk_column value fetched from step 1, and when the buffer is full sort them by….89G 1.53G Innodb_data_reads 120552 123872 100551 103011 77213 Innodb_pages_read 120548 123868 100551 123592 100566 Innodb_rows_read 799239…
Post: MySQL Users Conference - Innodb
May 9, 2007 By 6 Comments
… – Innodb. Innodb Storage Engine was covered in a lot of talks, many of them done by Innodb users. I found these items forth interest Innodb… out ALTERing Innodb tables may take a lot of time. Fast Index creation will allow Innodb to build indexes by sorting rather by row by row… or static record format ? (static record format for sort used by MyISAM may cause sort files to be much larger than table itself…
Post: MySQL Indexing Best Practices: Webinar Questions Followup
August 16, 2012 By 4 Comments
… need to sort by some 3rd column, say C index (A,B,C) would not work as range will prevent sorting from using… filesort for group by by this column. This works because by scanning data in index order MySQL gets data in already sorted order and… you can use and index for “order by desc” indicates a double linked list. Innodb has double linked list – each leaf page…
Post: What exactly is read_rnd_buffer_size
July 24, 2007 By 4 Comments
… only by MyISAM. It is used for some sorts to optimally read rows after the sort. Here is how it works: As sort is… key values for Innodb or storing full data which is being retrieved (good for small data lengths). In case sort with row… read_rnd_buffer to optimize data retrieval – As data is sorted by the key value it needs to be accessed in pretty…
Post: Building Indexes by Sorting In Innodb (AKA Fast Index Creation)
June 19, 2012 By 2 Comments
Innodb can indexes built by sort since Innodb Plugin for MySQL 5.1 which is a lot faster … fixed this in their tree back in early 2011 adding innodb_merge_sort_block_size variable and I was thinking this small… building index by sort with small buffer – this comes from building index on long character field with very short length, Innodb would use…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 4 Comments
… Key-ordered scan, the secondary key on col1 would be sorted by col1 i.e. in index order and then the lookup… 144798 144881 Innodb_rows_read 4127318 6718351 6611675 6707882 5479445 5527245 Select_scan 1 1 1 1 1 1 Sort_scan 1 1 1 1 1 1 The first obvious improvement is shown by the high numbers of Innodb_buffer…
Post: Enum Fields VS Varchar VS Int + Joined table: What is Faster?
January 24, 2008 By 30 Comments
… be larger. It is also interesting to note performance of Innodb tables in this case: for VARCHAR it takes about 0… sorting by name we have to perform the join for each row to retrieve it. This also means sort can’t be done by… course arrange state ids in the alphabetical order and do sort by state_id, though join cost still could be significant. And…
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 19 Comments
… create physically sorted indexes with Innodb (with index built by sort) this is when this should be helpful the most. Q3: Does Innodb secondary Indexes…? HT: Yes. However, work has been done on it by Inaam. Q19: INNODB uses it’s own internal buffer pool but itâ… threads waiting for semaphores in SHOW INNODB STATUS), you can try to disable thread throttling completely by setting the value 0. But…
Post: ALTER TABLE: Creating Index by Sort and Buffer Pool Size
June 27, 2012 By 4 Comments
… status like “sbtest” \G *************************** 1. row *************************** Name: sbtest Engine: InnoDB Version: 10 Row_format: Compact Rows: 10000060 Avg_row_… fit to memory any more. Creating Index by sort is great Creating index by sort can provide over 20x performance improvement to …
