Re: Monitoring large resultsets

[Aftab Khan]

>> So global eXclusive lock is used while invalidation take place
That means that any other SELECTs -- regardless of what table(s) they are touching -- are stalled waiting for the invalidation to finish.

That's how query_cache works, for writes queries, invalidation process is costly when cache is fragmented and/or large (when it's configured to use large memory).


>Vertical partitioning is useful IF it cuts down on disk hits. My mantra for big systems "Count the disk hits".
>> | 1 | SIMPLE | jos_content | range | idx_section,idx_state,idx_catid | idx_state | 1 | NULL | 38791 | Using where |
>If the average row is 14K, then 38791 * 14K = 500MB is a lot of stuff to shovel through. (That's even before getting to the other two tables!) That _may_ involve creating a temp table of 500MB.


In this case, its not creating temp table, so its a WASTE of effort/time to consider vertical partitioning.



Edited 1 time(s). Last edit at 07/14/2012 02:43AM by Aftab Khan.