… when the buffer is full sort them by pk_column, and do a range primary key lookup as follows: SELECT non_key_column… Plan id select_type table type possible_keys key key_len ref rows filtered Extra 1 SIMPLE orders range PRIMARY,i_o… lookups as well. But this works only with joins and specifically with Block Access Join Algorithms. So I am not going to…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…idblogpercona.commanual interactive_timeoutblogpercona.commanual join_buffer_sizeblogpercona.commanual keep_…commanual Select_full_joinblogpercona.commanual Select_full_range_joinblogpercona.commanual Select_rangeblogpercona.commanual Select_range_checkblogpercona.commanual Select_scanblogpercona…
Comment: MySQL Server Memory Usage
September 1, 2006 By 18 Comments
…_revoke_all’, ’0′ ‘Com_rollback’, ’4666272′ ‘Com_savepoint’, ’0′ ‘Com_select‘, ’378247551′ ‘Com_set_option’, ’285487367′ ‘Com_show_binlog_events’, ’0…_blocks’, ’498′ ‘Questions’, ’1462755007′ ‘Rpl_status’, ‘NULL’ ‘Select_full_join‘, ’0′ ‘Select_full_range_join‘, ’0′ ‘Select_range‘, ’5683551′ ‘Select_range_check’, ’0′ ‘Select_scan’, ’1104831′ ‘Slave_open_temp_tables’, ’0′ ‘Slave…
Post: How adding another table to JOIN can improve performance ?
August 1, 2008 By 12 Comments
…full key while only first key part is used. Let us now replace the range…JOIN to get list of days matching range from some pre-generated table and use the join…*************************** 1. row *************************** id: 1 select_type: SIMPLE table: dl type: range possible_keys: PRIMARY key: …
Post: Joining on range? Wrong!
May 17, 2010 By 10 Comments
… sold yesterday. SELECT COUNT(1) FROM tags t JOIN products p ON p.prd_id = t.tag_prd_id JOIN items_ordered i… 3rd row key_len is only 4 bytes, while the full key length is 4 bytes for `itm_prd_id` plus… affects joins only. When you use a range condition on the first (or the only) table, it works as expected: EXPLAIN SELECT COUNT…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 139 Comments
… or not depends on index selectivity – how large proportion of rows matches to particular index value or range. What is often forgotten…, so range 1..100 selects about 1% of the table. The times for full table scan vs range scan by index: mysql> select count(pad… reduce the gap but I doubt it will be closed. Joins Joins are used to compose the complex object which was previously…
Post: Identifying the load with the help of pt-query-digest and Percona Server
December 29, 2011 By 3 Comments
…0 # InnoDB_trx_id: F00 # QC_Hit: No Full_scan: Yes Full_join: No Tmp_table: No Tmp_table_on_disk… see majority of the time lies in the range >= 10ms and < 100ms. The "Tables" section lists the... EXPLAIN /*!50100 PARTITIONS*/ SELECT t.*, tt.*, tr.object_id FROM wp_terms AS t INNER JOIN wp_term_taxonomy …
Post: MySQL EXPLAIN limits and errors.
July 24, 2006 By 6 Comments
…join the problem on looking at too many table join combinations in joins…full number. Here is example: mysql> explain select * from lt limit 10; +—-+————-+——-+——-+—————+———+———+——+——+————-+ | id | select… values (or even range) may be perfoming …
Post: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 22 Comments
… GROUP BY Carrier) t JOIN (SELECT Carrier, count(*) AS c2 from ontime_fact join dim_date using(date_id) join dim_flight using(flight… the size of the date range: — Q8.0 SELECT dest.CityName, COUNT( DISTINCT origin.CityName) from ontime_fact JOIN dim_airport dest on… a checkout from SVN) here: Shard-Query Google code project Full disclosure Justin Swanhart, the author of this article is also…
Post: ORDER BY ... LIMIT Performance Optimization
September 1, 2006 By 93 Comments
…full result set, so it is important for it to use index – in this case index range…it is effectively removed from join execution (replaced with…select * from test order by k limit 5; +—-+————-+——-+——-+—————+——+———+——+———+——-+ | id | select_type | …
