Either the key cache is inefficient or I misunderstand it. Can anyone
explain this?
Before query:
| Key_blocks_used | 530300 |
| Key_read_requests | 56072940 |
| Key_reads | 527026 |
Query executed, takes 30+ seconds
After Query
| Key_blocks_used | 530300 |
| Key_read_requests | 56092143 |
| Key_reads | 527026 |
No increase in key_reads, so lookup came from cache
Same Query run again takes 0.11 seconds (272 times faster)
How can a query that uses only cached indexes and read only from RAM cache
both times run faster the second time, when NOTHING WAS READ FROM disk?
If I wait long enough, it will again take 30+ seconds as if it were removed
from the cache, even though key_buffer_size=560M. It should have 30M to
spare according to Key_blocks_used. But it's not removing it from the cache
or Key_reads would increase when it reloaded.
Am I misunderstanding something or is the key cache really this inefficient?
Thanks in advance
