…PRIMARY KEY (`transactionid`), KEY `marketsegment` (`price`,`customerid`), KEY `registersegment` (`cashregisterid`,`price`,`customerid`), KEY `pdc` (`price`,`dateandtime`,`customerid`) ) ENGINE=InnoDB…index and only a primary index, and against the table purchases_index which has 3 secondary indexes….
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
… secondary index definition (and hence covering index optimization is not used), then primary key lookups have to be performed for each secondary key …: SELECT key_column, pk_column FROM tbl WHERE key_column=x ORDER BY key_column (Note that secondary keys in InnoDB contain primary key columns) …
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
… is, and what is it aimed at. Index Condition Pushdown Traditional B-Tree index lookups have some limitations in cases such as range scans, where index parts after the part on which range condition is applied… for filtering records. For example, suppose you have a key defined as: KEY `i_l_partkey` (`l_partkey`,`l_quantity`,`l_shipmode…
Comment: What does Using filesort mean in MySQL?
March 15, 2012 By 27 Comments
… could not find a reason why MySQL does not use index in the following scenario: CREATE TABLE table1 ( id bigint(20…) DEFAULT NULL, PRIMARY KEY (id), KEY (a), KEY (b) ) ENGINE=InnoDB Table 1 has 512000 randomly generated rows. This query uses index (type: index, key: a, key_len: 103…
Post: InnoDB: look after fragmentation
November 5, 2009 By 12 Comments
…` int(10) unsigned default NULL, PRIMARY KEY (`tracker_id`,`username`,`time_id`), KEY `block_id` (`block_id`) ) ENGINE=InnoDB Table has 11864696 rows and… likely than by primary key, and you cannot really control it (tough it is possible in XtraDB / InnoDB-plugin with FAST INDEX creation) so…
Post: MySQL Optimizer and Innodb Primary Key
October 3, 2006 By 9 Comments
… primary key order: mysql> explain select * from innodb order by id \G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: pktest type: index possible_keys: NULL key: PRIMARY key_len: 4…
Post: Long PRIMARY KEY for Innodb tables
October 3, 2006 By 8 Comments
… PRIMARY KEYs with Innodb tables due to the fact all other key will refer to the rows by primary key. I also recommended to use sequential primary keys… if extra indexes are defined. The primary key itself does not get much larger whatever columns you place into it, as primary key BTREE contains…
Post: Recovering Innodb table Corruption
July 4, 2008 By 19 Comments
…stored already) 6353 InnoDB: Page may be an index page where index id is 0 25556 InnoDB: (index “PRIMARY” of table “test”.”test”) InnoDB: Database page corruption… DEFAULT NULL, -> `id` int(10) unsigned NOT NULL AUTO_INCREMENT, -> PRIMARY KEY (`id`) -> ) ENGINE=MYISAM; Query OK, 0 rows affected (0.03…
Post: How to recover deleted rows from an InnoDB Tablespace
February 20, 2012 By 3 Comments
…_INDEX/ 0-26 0-27 In this case, there are two indexes with the IDs 0-26 and 0-27. InnoDB has Clustered Primary Key, that is, the data is organized along with the primary key… Primary Key There are different methods to find the correct index and here I’m going to explain three of them: A) INNODB_SYS_INDEXES…
Post: Extending Index for Innodb tables can hurt performance in a surprising way
May 22, 2010 By 9 Comments
… from Innodb specific feature – index entries being sorted by primary key for each complete key value. So when you have index (a) and id is a primary key…-duplicate-key-checker key checker when it comes to redundant indexes. If you have query plans depending on Innodb ordering of data by primary key inside indexes…
