Marc Cousin wrote:
Le Thursday 16 July 2009 22:07:25, Kevin Grittner a écrit :
Marc Cousin <cousinmarc@xxxxxxxxx> wrote:
the hot parts of these 2 tables are extremely likely to be in the
database or linux cache (buffer hit rate was 97% in the example
provided). Moreover, the first two queries of the insert procedure
fill the cache for us...
Ok, so to sum it up, should I keep these values (I hate doing this :) ) ?
Would there be a way to approximately evaluate them regarding to the expected
buffer hit ratio of the query ?
cached_buffer_cost = 0.01
effective_page_cost =
((1 - expected_cache_hit_ratio) * standard_page_cost)
+ (expected_cache_hit_ratio * cached_buffer_cost)
If your assumption is only about these queries in particular, rather
than applicable across the board, you should set the page_costs just for
this query and reset them or close the connection after.
--
-Devin
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