From: | PG Doc comments form <noreply(at)postgresql(dot)org> |
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To: | pgsql-docs(at)lists(dot)postgresql(dot)org |
Cc: | splarv(at)ya(dot)ru |
Subject: | explanation for random_page_cost is outdated |
Date: | 2020-02-27 14:48:44 |
Message-ID: | 158281492445.30439.15446208692175239579@wrigleys.postgresql.org |
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Lists: | pgsql-docs |
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/12/runtime-config-query.html
Description:
Explanation for random_page_cost is rather outdated, because it did only for
case of mechanical hdd. But all modern database servers, which I know, made
upon SSD. Do or not do default value for random_page_cost equal to 1 is the
question, but, IMHO, at list in the documentation about random_page_cost
need to add in a speculation about SSD.
It's important because a business programming now is mostly web programming.
Most database is poorly designed by web programmer, tables looked like a
primary key and a huge json (containing all) with large gin index upon it.
Now I am seeing a table with a GIN index 50% of the table size. The database
is on SSD, of cause. With default random_page_cost=4 GIN index don't used
by planner, but with random_page_cost=1 the result may be not excellent, but
acceptable for web programmers.
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