… 255] (inclusive). Quorum is computed using weighted sum over group members. Percona XtraDB Cluster …. Bug fixed #1130888 (Seppo Jaakola). If MySQL replication threads were started before running wsrep…rsync SST filter, this caused the SST failure due to insufficient privileges. Fixed by excluding …
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
… you didn’t take it apart. Projection, GROUP BY, SUM, COUNT, MIN*, and MAX* are distributable. With a…set, all in parallel. All joins, aggregation and filtering is done at the storage node level. This…resource which speaks SQL, but right now only MySQL storage nodes are supported. Amdahl’s law applies…
Post: Researching your MySQL table sizes
March 17, 2008 By 28 Comments
…MySQL Instance SELECT count(*) tables, concat(round(sum(table_rows)/1000000,2),’M') rows, concat(round(sum… using some filter I often use similar queries to find space used by particular table…(sum(index_length)/sum(data_length),2) idxfrac FROM information_schema.TABLES GROUP BY engine ORDER BY sum…
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
… enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a look at and benchmarking optimizer enhancements one by one… optimizer enhancement Index Condition Pushdown (ICP). Its available in both MySQL 5.6 and MariaDB 5.5 Now let’s take… on which range condition is applied cannot be used for filtering records. For example, suppose you have a key defined as…
Post: How fast can MySQL Process Data
April 9, 2008 By 3 Comments
…filtering speed stays about the same: mysql> select count(*) from m3; +———-+ | count(*) | +———-+ | 10476840 | +———-+ 1 row in set (0.00 sec) mysql…mysql> select sum(i) from m3; +———+ | sum(i) | +———+ | 3492290 | +———+ 1 row in set (1.86 sec) mysql…
Post: Hidden columns of query_review_history table
August 28, 2012 By Leave a Comment
… pt-query-digest to process a MySQL slow query log and store historical values for … an underscore followed by any of these MAGIC_history_cols values: pct|avt|cnt|sum|min|max|pct…,t=query_review_history,p=pass,u=percona \ –filter=” \$event->{Bytes} = length(\$event->{arg}) and \$event->{hostname}=\”$…
Post: Multi Range Read (MRR) in MySQL 5.6 and MariaDB 5.5
March 21, 2012 By 10 Comments
…the buffer size. In MySQL 5.6 the buffer size used by MRR can be controlled by the variable read_…The query used is: select c_custkey, c_name, sum(l_extendedprice * (1 – l_discount)) as revenue, c_acctbal… type possible_keys key key_len ref rows filtered Extra 1 SIMPLE nation ALL PRIMARY NULL NULL …
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
… the top queries with largest impact – longest sum of run time which typically (not always) …by MySQL. The end result might be that you end up limiting the number of results returned by the query, by using a LIMIT clause or by filtering based on the …
Post: A rule of thumb for choosing column order in indexes
June 5, 2009 By 15 Comments
… come first in an index. This is not specific to MySQL, it’s generally applicable to any database server with b…
Post: Intro to OLAP
July 12, 2010 By 10 Comments
… (or online analytical processing) tools using MySQL and other free open source software…. it would usually be aggregated with SUM. The other information about the sale,…by product, by category, and by region. The information is presented in such a fashion that it can be “drilled into” and “filtered…
