…even though it already tried pretty hard to keep working despite recoverable errors and such. Whereas pt-osc … 5.5) for metadata locks. Now –set-vars is used to set both of these (or any) system … and tcpdump), so you shouldn’t have a problem finding queries to run and compare. pt-query-digest …
Post: Understanding the maximum number of columns in a MySQL table
April 8, 2013 By 5 Comments
…4096. This, however, is not the true limit. To find out what the actual limit is, we must …number of columns you can create. If you try setting the storage engine to InnoDB however, you will …columns error with only 192 columns (i.e. 191 worked): sub cname ($$) { my $c=shift; my $name=”"; while($c >…
Post: Galera Flow Control in Percona XtraDB Cluster for MySQL
May 2, 2013 By 5 Comments
… is existence of a replication feedback mechanism, unlike anything you find in standard async MySQL replication. It is my belief that… the wsrep_provider_options global variable. gcs.fc_limit This setting controls when flow control engages. Simply speaking, if the wsrep…: mysql> set global wsrep_provider_options=”gcs.fc_limit=500; gcs.fc_master_slave=YES; gcs.fc_factor=1.0″; Working with…
Post: Open Source, the MySQL market (and TokuDB in particular)
May 10, 2013 By 13 Comments
… it is quite hidden among all buzz, but you can find some grains of truth in the article “Dead database…Source product, you also need a business model that works. And be sure: the Open Source game is a…under proprietary license (not an Open Source one) you set the bar to success high and you will have…
Post: Quickly finding unused indexes (and estimating their size)
December 5, 2012 By 2 Comments
… dump and load a copy of that table into your working index_analysis schema. Merging stats from several servers In the…: last_name 1 row in set (0.03 sec) Now I need a way to find the set of indexes in all_indexes… | staff | idx_fk_store_id | 0.02 | +————–+—————+—————————–+—————+ 22 rows in set (0.02 sec) Recovering filesystem space Now astute innodb experts…
Post: How does MySQL Replication really work?
January 9, 2013 By 9 Comments
… MySQL replication really works on the high level. Or it’s been so long ago I can’t even find it. So… for SQL thread to get a good picture. If you find that replication is CPU bound, this maybe very helpful. If…-bound replication is to increase the amount of memory so working set fits in memory. Another – get IO device that can do…
Post: Heikki Tuuri answers to Innodb questions, Part II
November 4, 2007 By 13 Comments
… performance of Innodb on Solaris? HT: Yes, if your ‘write working set‘ fits in 16 GB. I mean, if the database buffer… working set is, say, 100 GB, then increasing the buffer pool size does not help. PZ: I should note for most application working set… helped us greatly to spot scalability problems and find fixes for them. The work continues. I believe improving scalability is a continuous…
Post: How to find MySQL queries worth optimizing ?
September 11, 2012 By 6 Comments
One question I often get is how one can find out queries which should be optimized. By looking at pt-query-digest report it is easy to find slow queries or queries which cause the large portion of… row set which is expected as we have 2 (logical) tables used in the query. This rule also does not work if…
Post: MySQL 5.6 vs MySQL 5.5 and the Star Schema Benchmark
March 11, 2013 By 7 Comments
… detailed my findings here. Just a few notes: I tested two scenarios: a buffer pool much smaller than the data set (default… smaller than the working set) having innodb_old_blocks_time=1000 appears to cause a major performance regression. The new setting changes which… performance? Each “flight” of queries represents a set of drill-down queries to find an anomaly. I am going to focus on…
Post: MySQL performance on EC2/EBS versus RDS
August 4, 2011 By 11 Comments
…-heavy, you generally need the actively accessed set of data (what we call the working set) to fit in the InnoDB buffer pool… write-heavy databases, you are generally bound by either the working set size versus the buffer pool size, or the sheer volume… you could find that you generate more I/O than you can push to EBS, even if the working set size is not…
