Heikki Linnakangas a écrit :
Arnaud Lesauvage wrote:
This query was taken from my "adminsitrative areas" model (continents,
countries, etc...). Whenever I query this model, I have to join many
tables.
I don't really know what the overhead of reading the heap-tuples is, but
would it be a good idea to add data-redundancy in my tables to avoid
joins ? (adding country_id, continent_id, etc... in the "cities" table)
It depends. I would advise not to denormalize unless you really really
have to. It's hard to say without more knowledge of the application.
Is the query you showed a typical one? It ran in about 160 ms, is that
good enough? It's doesn't sound too bad, considering that it returned
almost 40000 rows.
It is quite typical, yes. It is the base query of a view. In
fact, most views have a lot more joins (they join with all
the upper-level tables).
But 150ms is OK, indeed.
