… random selection only work when the IDs for movies are distributed uniformly over the range 1..MAX(id)? Yes, there’s a risk if you have irregular distribution of matching rows that you’ll get skewed results… the keywords were returned in a different order from what you specify in the query? The tuple comparison you’re referring to…
Comment: Percona XtraBackup 2.1.3 for MySQL available for download
May 30, 2013 By 3 Comments
…=52428800 read_buffer_size=131072 max_used_connections=13 max_threads=2002 thread_count=6 …get some variables. Some pointers may be invalid and cause the dump to abort. Query (0): is an invalid pointer Connection ID (thread ID…130528 09:53:56 mysqld_safe mysqld from pid file /var/lib/mysql/srv-d2…
Post: Virident vCache vs. FlashCache: Part 2
May 17, 2013 By 3 Comments
… include the numbers from the vCache…appears to get *better* over …max_heap_table_size = 64M sort_buffer_size = 4M join_buffer_size = 4M thread_cache_size = 1000 query_cache_size = 0 query_cache_type = 0 ft_min_word_len = 4 thread_stack = 192K tmp_table_size = 64M serverÂid…
Post: Flexviews - part 3 - improving query performance using materialized views
April 4, 2011 By 20 Comments
…( -> flexviews.get_id(‘demo’,'dashboard_customer_sales’)); Query OK, 0 rows affected (41 min 52.04 sec) *If you use MIN/MAX/COUNT_DISTINCT… delete some line items from orders: mysql> delete -> from order_lines -> where order_id -> between 1 and 100 -> limit 500; Query OK, 484 rows…, the last parameter is a transaction id number, which is usually obtained with flexviews.get_uow_id_from_datetime() function. If you pass a…
Post: Recovering Innodb table Corruption
July 4, 2008 By 22 Comments
…* from test limit 300; ERROR 2013 (HY000): Lost connection to MySQL server during query As you can see I can get rows from … select max(id) from test2; +———+ | max(id) | +———+ | 220 | +———+ 1 row in set (0.00 sec) mysql> insert ignore into test2 select * from test where id>250; …
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
… total min max avg 95% stddev median # ============ ======= ======= ======= ======= ======= …id FROM wp_terms AS t INNER JOIN wp_term_taxonomy AS tt ON tt.term_id = t.term_id…Get yourself Percona Server, turn on log_slow_verbosity and start using pt-query-digest”, your job of identifying queries…
Post: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 23 Comments
…max(FlightDate) from dim_dateG *************************** 1. row *************************** count(*): 8401 min(FlightDate): 1988-01-01 max…get Shard-Query (currently in development release form as a checkout from SVN) here: Shard-Query…
Post: Wrong GROUP BY makes your queries fragile
September 6, 2006 By 7 Comments
…query something like SELECT A,B,MAX(C) FROM TBL GROUP BY A – what would you expect from such query…get ? In fact this is where results becomes non-deterministic and fragile – any B from…
Comment: MySQL Partitioning - can save you or kill you
July 31, 2012 By 45 Comments
… this query: SELECT * FROM `tag` ORDER BY RAND() LIMIT 0,30 The server dies for about 2-3 seconds SELECT * FROM `tags` WHERE id >= FLOOR(RAND()*( SELECT MAX(id) FROM tags)) LIMIT 0,30 This works preatty fast but its not really random, i get 50% duplicates on each query Any…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
…from the ./run_query command, called pivot_results cd shard-query/ $ ./run_query < queries…max-allowed-packet=1M net-buffer-length=16K #we value throughput over response time, get…
