…/multiple joins vs. multiple queries (e.g. temp tables)? …selection only work when the IDs for movies are distributed uniformly over the range 1..MAX… to look up values against multiple columns in …MySQL Conference and Expo in Santa Clara, California starting March 31, 2014. Watch more webinars from…
Post: Recovering Innodb table Corruption
July 4, 2008 By 22 Comments
… So what can you do to recover such a table ? There are multiple things which can get corrupted and I will …try some higher values mysql> select max(id) from test2; +———+ | max(id) | +———+ | 220 | +———+ 1 row in set (0.00 sec) mysql> insert ignore into test2 select * from test where…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 20 Comments
…tables used by the above view, as stored in the data dictionary: mysql> select * from flexviews.mview_table…value, then it refreshes the view up to the latest changes which have been collected. You can use this to refresh multiple…
Post: Using any general purpose computer as a special purpose SIMD computer
May 16, 2011 By 5 Comments
…FROM words2 AS `words2` GROUP BY 1,2,3 ORDER BY NULL ) The other important optimization combines results from multiple…VALUES(`word`), `md5(word)`=VALUES(`md5(word)`), `count(*)`=`count(*)` + VALUES…mysql> select min(id),max(id) from words; +———+———+ | min(id) | max…
Post: Efficient Boolean value storage for Innodb Tables
April 23, 2008 By 6 Comments
…task of storing multiple of boolean values (yes/now or something similar) in the table and … Avg_row_length: 11 Data_length: 23068672 Max_data_length: 3096224743817215 Index_length: 1024 Data…of flag values means you can’t use normal “=” comparison operator with them: mysql> select count(*) from …
Post: Edge-case behavior of INSERT...ODKU
October 27, 2012 By 6 Comments
…MySQL checks our INSERT, sees that the next auto-inc value… what’s in our table: (root@localhost) [test]> select * from update_test; +————+———-+———+———————+ | id | … the auto-increment max value, which is the one…… ODKU on a table with multiple unique indexes such …
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
…multiple…VALUES(`sum(DepDelay >= 0) flight_delayed`) — SQL TO SEND TO SHARDS Array ( [0] => SELECT…FROM `aggregation_tmp_74082863` GROUP BY 1 –POST EXEC: DROP TABLE IF EXISTS `aggregation_tmp#74082863` ; Edit *MIN/MAX…
Post: A case for MariaDB's Hash Joins
May 31, 2012 By Leave a Comment
…multiple hash tables would be created. For example if the left operand has “n” rows, and its size is three times the value…returned by MySQL 5.5 is as follows: SELECT s_nationkey, l_shipmode, count(*) FROM supplier INNER…the sense that it always uses the max values join algorithm. If join_cache_level=…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
…splitting and/or loading among multiple nodes as well. Note… from 1988 to 2010′; mysql> use ontime1; Database changed mysql> show table status like… the third parse time). $ echo “select count(*) from ontime_fact;” | ./run_query Array ( [… max-allowed-packet=1M net-buffer-length=16K #we value …
Post: MySQL Server Variables - SQL layer or Storage Engine specific.
June 8, 2006 By 14 Comments
…tables only to optimize bulk inserts (multiple value inserts). Really helps if you have really bulk inserts 100-1000+ values…tables. max_write_lock_count Variable which may save you from read starvation if there are constant writes to the table. Works with table…
