…InnoDB/XtraDB. Tests show that PBXT’s performance is similar to InnoDB but, …rows that do not exist. This, in turn, means that PBXT transactions are not SERIALIZABLE. A result of this is that…rows are selected in this manner. I should also mention that the consequence of this is that SELECT …
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
… Range Read With traditional secondary index lookups, if the columns that are being fetched do not belong to the secondary index definition… depend on the number of rows that match the condition ‘key_column=x’. You can see that there are a lot of random primary… of the optimizer’s job to select the best query execution plan. I had noted a similar thing when benchmarking ICP, the…
Post: High-Performance Click Analysis with MySQL
December 22, 2008 By 13 Comments
… now contain only half as many rows. That will make the indexes less than… it on the master with INSERT..SELECT queries, it will propagate to …with tables that contain name-value pairs or something similar. The thought is that you can…that it’s not 100% optimal for. But if the costs of doing that are…
Post: Fishing with dynamite, brought to you by the randgen and dbqp
November 16, 2011 By Leave a Comment
… test case module that we can execute. All of the randgen test cases are structured similarly, so all … of tables: $tables = { rows => [1..50], partitions => [ undef ] }; The value in the ‘rows‘ section tells the … this as a possible WHERE clause for SELECT queries: WHERE X . char_field_name != ‘If …
Post: A micro-benchmark of stored routines in MySQL
August 16, 2009 By 7 Comments
…be shortcomings that are …rows: 4079 Extra: Using where *************************** 2. row *************************** id: 2 select_type: DEPENDENT SUBQUERY *************************** 3. row *************************** id: 2 select…similar to the first table shown above, but the further two rows are…
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
… enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a look at and benchmarking optimizer enhancements one by…
Post: Replaying database load with Percona Playback
October 25, 2012 By 9 Comments
… we are logging all queries that are …that a particular query returns different number or rows. For example: Connection 43 Rows Sent: 210 != expected 211 for query: SELECT…rows, got 371851 (a difference of 611) Number of queries where number of rows differed: 324. Not too many changes, is very similar…
Post: Should MySQL Extend GROUP BY Syntax ?
August 17, 2007 By 11 Comments
… see if you want to get one row from the group which is sorted some … that because you’re soring by population you would see MAX(Population) in the population column: SELECT…similar case. SQL Standard might be good for enterprise applications but huge amount of Web applications do not care – they are…
Post: Read/Write Splitting with PHP Webinar Questions Followup
January 23, 2013 By 4 Comments
… Q: Are there similar …that SELECTs will block until all previously queued changes are executed. Therefore you can have assurance that…that‘s true, Row-Based Replication (RBR) can be faster than Statement-Based Replication (SBR). But there are…that are ephemeral and easily recreated. Anything that…
Post: Percona XtraDB Cluster reference architecture with HaProxy
June 20, 2012 By 63 Comments
…the operating system, the instructions are similar for any Linux distribution. … requested state transfer from ‘*any*’. Selected 1 (ip-10-112-39-… identified by ‘clustercheckpassword!’; Query OK, 0 rows affected (0.00 sec) mysql> …because MySQL will think that the connections are always coming from the…
