…mysql> select sum(data_length+index_length) from information_schema.tables where engine=’memory’; +——————————-+ | sum(data_length+index_length) | +——————————-+ | 126984 | +——————————-+ 1 row in set…
Post: InnoDB's gap locks
March 27, 2012 By 15 Comments
…is normal and expected that query results can change during a transaction, so there is no need to create locks to prevent that from…is a good source of information: http://dev.mysql.com/doc/refman/5.1/en/innodb-locks-set.html. Conclusion MySQL…
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
…result set is treated as a materialized view over a union of all the already joined and aggregated data from…MySQL storage nodes are supported. Amdahl’s law applies to the distributed processing. The results from…result set merge optimization enabled: ON DUPLICATE KEY UPDATE…
Post: PHP Large result sets and summary tables.
July 6, 2007 By 8 Comments
…mysql_use_result API call which does not store all result set in memory but instead streams it from…no more works If you use buffered query you can use same connection to run other queries, ie INSERTs and UPDATEs while you traverse with data. Not with unbuffered query because connection is …
Post: Upgrading MySQL
January 5, 2010 By 23 Comments
…is change of TIMESTAMP output format in MySQL 4.1 or changing JOIN evaluation in 5.0 (which could both cause different result set…MySQL functionality which is unlikely to be affected. If you’re something like SELECT name FROM…data is the same. It is possible some update…
Post: Troubleshooting MySQL Upgrade Performance Regressions
February 15, 2012 By Leave a Comment
…RESULT/SMALL_RESULT. Check whatever stats are the same (run SHOW INDEXES FROM…from optimizer standpoint and updating stats may cause old MySQL…is possible for stats to be different for the same data because it uses random sampling to update…
Post: Preprocessing Data
August 8, 2011 By 3 Comments
… results from …set…is a form of batch processing. Examples could be reporting, updating caches (preventing cache stampedes) and counter tables. Prefetching If there is…result. Examples could be pagination. On Request If there is no good way to preprocess the data then you just have to send the result…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
… data sets. For example I’m using Query Cache on server which runs this blog. Updates are rather rare so per-table granularity is… derived from this table are invalidated at once. Most of them quite likely would not have change their result set but MySQL has no way to identify which one of them would so it gets rid of all of them. This is…
Post: MySQL-Memcached or NOSQL Tokyo Tyrant - part 1
October 15, 2009 By 16 Comments
… into using a database like MySQL with no thought into whether if …Is the database even the best place for this data? I decided to walk through setting…Update data from that row and replace the stored contents on disk C.) Use the data from… up the result via that key. It then uses data from that random…
Post: Using Flexviews - part one, introduction to materialized views
March 23, 2011 By 2 Comments
…is lower because incremental refresh is faster than recomputing the contents from scratch. The contents of the result set are updated…no outer join), no non-deterministic functions, etc. There is overhead for change-data capture. Some extra storage is…
