The query is slow because first, this query has an OR condition which cannot be optimized with a single index (while conditions with only AND can) and second, because besides the emails, it has to check the isActive=1 condition. So it prefers to do a table scan. The other possible pat...
Still this query runs very slow. I've run explain, this is the output: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE A index \N PRIMARY 767 \N 23269 Using index 1 SIMPLE B ALL \N \N \N \N 70041 Using where; Not exists UPDATE: SHOW CREATE TABL...
Re: Slow query. Why is it slow? Phillip Ward May 20, 2013 09:00AM Re: Slow query. Why is it slow? Rick James May 20, 2013 11:20PM Re: Slow query. Why is it slow? ben jaz May 23, 2013 06:21PM Re: Slow query. Why is it slow?
It is a feature-rich open-source MySQL proxy solution, that allows query routing for the most common MySQL architectures (PXC/Galera, Replication, Group Replication, etc.). It allows sharding by configuring a set of backend servers (shards) and a set of query rules, to route the applicatio...
0 MySQL LIMIT and OFFSET messing up my results order 4 Limit with offset ("LIMIT 500000, 10") is slow even after index? 2 How to optimize MySQL ORDER BY + huge LIMIT Offsets 1 Very slow query when using ORDER BY and LIMIT? 1 Why the MySQL query slows down while using LIMIT wit...
On the other hand, a join of a few large tables, which is completely disk-bound, can be very slow. One of the reasons elevating this problem in MySQL is a lack of advanced join methods at this point (the work is on a way) – MySQL can’t do hash join or sort-merge join – ...
(with exeption of MySQL Cluster) and MySQL issues IO requests one by one for query execution, which means if single query execution time is your concern many hard drives and large number of CPUs will not help. Sometimes it is good idea to manually split query into several, run in parallel...
You have a constant lookup when tm.owner_id is present, which leads MySQL optimizer to decide it win over a range scan. In the book High Performance MySQL, there is one chapter discussing the query optimization. There is one technique called: join decomposition, i.e., to separate one big...
I've tried moving the "Options" bit *AFTER* Type/isValidated, but it still seems too slow. Removing the "Options" part of the query drops it down to 0.0045 seconds.. which is more like what I would expect! I've got an index setup for the query... but maybe there is more I can...
> worry that the Query Cache is involved. Please > turn off the QC (or use SQL_NO_CACHE) when doing > timings. > > How close to the end of the table is id=5809978 > (the fast Query#7)? How far from the end is > 5490881 (the slow Query#9)? The diff value is the ...