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Re: HTON_FAST_KEY_READ

 

Hi,

Here's what the original MySQL comments say:

/*
Reading keys in random order is as fast as reading keys in sort order
(Used in records.cc to decide if we should use a record cache and by
filesort to decide if we should sort key + data or key + pointer-to-row
*/
#define HA_FAST_KEY_READ (1 << 5)

I think it's formally not true for PBXT, if by "reading in sort order" they mean index scan.And here's the comment in PBXT :

/* Since PBXT caches read records itself, I believe
* this to be the case.
*/
HA_FAST_KEY_READ |

I guess this flag was initially intended for the case when the engine maintains a linear list of index leafs, so index scan is O(n). This is formally true for InnoDB but I think this flag might make sense for PBXT as well because the of the generally more effective index caching as mentioned in the comment.

14.05.2010 10:26, Paul McCullagh пишет:
Hi Brian,

Good question, I am not sure why that flag is set. Maybe Vlad has an idea...

What does the flag mean?

On May 13, 2010, at 11:16 PM, Brian Aker wrote:

Hi!

I was noticing that PBXT supports HTON_FAST_KEY_READ, is this really the case?

Thanks,
-Brian
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Paul McCullagh
PrimeBase Technologies
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