… had time for during the session, but here are all the … variety of queries. The query optimizer analyzes queries for common patterns the MySQL designers know … uniformly over the range 1..MAX(id)? Yes, there’s a…per production year for each kind_id. It was more efficient in this case to force MySQL…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…session_cache_missesblogpercona.commanual Ssl_session_cache_modeblogpercona.commanual Ssl_session_cache_overflowsblogpercona.commanual Ssl_session_cache_sizeblogpercona.commanual Ssl_session_cache_timeoutsblogpercona.commanual Ssl_sessions…
Post: Troubleshooting MySQL Memory Usage
March 21, 2012 By 5 Comments
…sessions have created which temporary tables (both in memory and not): mysql> select * from information_schema.global_temporary_tables \G *************************** 1. row *************************** SESSION…
Post: Review of MySQL 5.6 Defaults Changes
October 8, 2012 By 10 Comments
… of defaults changes in MySQL 5.6 compared to MySQL 5.5 In general… go over them: back_log = 50 + ( max_connections / 5 ) capped at 900 – The…just default at 2000 ? innodb_file_per_table =1 Great! We found it… variable to higher values for sessions executing complicated queries. I think this piece of…
Post: 10+ Ways to Crash or Overload MySQL
November 13, 2007 By 20 Comments
… parse tree inside MySQL which of course depends on query size which is controlled by max_allowed_packet. However some MySQL optimizations such as…. Session variables There is no restriction on how large you can set per connection variables for unprivileged user which allows to run queries…
Post: Investigating MySQL Replication Latency in Percona XtraDB Cluster
March 3, 2013 By 13 Comments
…synchronous replication behavior: mysql> set global wsrep_causal_reads=1; Query OK, 0 rows… thing is wsrep_causal_reads is session variables so you can mix different…mysql-user=root –mysql-password=”" –oltp-table-size=1000000 –num-threads=1 –init-rng=on –max-requests=0 –max-time=300 run …. per…
Post: How much memory Innodb locks really take ?
July 13, 2006 By 11 Comments
… Avg_row_length: 61 Data_length: 100253696 Max_data_length: 0 Index_length: 128974848 … 6092 LIST OF TRANSACTIONS FOR EACH SESSION: —TRANSACTION 0 42306982, ACTIVE 89 sec, process…per locked row; Now lets see how much exclusinve locks take: mysql> begin; Query OK, 0 rows affected (0.00 sec) mysql…
Post: Optimizing slow web pages with mk-query-digest
April 7, 2011 By 14 Comments
…queries that are consuming most MySQL time and that’s how mk-query-digest groups and orders data by default. Fixing top 10 queries…queries, I asked it to list me top slowest sessions: mk-query-digest –group-by=Thread_id –order-by=Query…
Post: Are PHP persistent connections evil ?
November 12, 2006 By 32 Comments
…MySQL server connections. Some people simply do not realize you can increase max_connections variable and get over 100 concurrent connections with MySQL… just few queries concurrently. If you have these queries doing …to mention about possibly changed per session variables. Many applications are fine …
Post: How is join_buffer_size allocated?
July 5, 2010 By 9 Comments
…MySQL configuration, …allocated per-thread (i.e. per-connection), this one is allocated per-join-per-… there’s no index. If the query joins several tables this way…=0; /* End sequentel */ 14271 size=max(thd->variables.join_buff_size, …server out of memory: set session join_buffer_size = 1 << 30; # 1GB…
