memcache vs.query_cache

Hi

(1) If memcache is available  - in an apache-php-mysql environment, does enabling or disabling of query_cache_type in mysql configuration, matter in improving performance? 

(2) If memcache is enabled and also query_cache_type is enabled, will both cache mechanism work or does one take precedence over the other, in serving requests.


(2) I just wanted to understand how these variables query_cache_type, tmp_table_size, max_heap_table_size, memory temporary tables influence each other?

In a replicated environment where query_cache_type is enabled and the tmp_table_size (64MB) and max_heap_table_size ( 1GB) the number of memory temporary tables created over a period of half-an-hour is around 2000.

Whereas if query_cache_type is disabled and the tmp_table_size(64 MB) and max_heap_table_size 91 GB) the number of temporary tables created over a period of half-an-hour is around 6000.

Can anyone please let me know what would be the explanation for the above? 
Should I bring down values of tmp_table_size and max_heap_table_size?

Thanks
Revathi R
 


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