Tomas Vondra <tv@fuzzy.cz> wrote:
> On 5.4.2012 15:44, superman0920 wrote:
>> Today I install PG and MySQL at a Server. I insert 850000 rows
>> record to each db.
>> I execute "select count(*) from poi_all_new" at two db.
>> MySQL takes 0.9s
>> PG takes 364s
> Are you sure the comparison was fair, i.e. both machines
> containing the same amount of data (not number of rows, amount of
> data), configured properly etc.?
Don't forget the "hint bits" issue -- if the count(*) was run
immediately after the load (without a chance for autovacuum to get
in there), all the data was re-written in place to save hint
information. I remember how confusing that was for me the first
time I saw it. It's very easy to get a false impression of overall
PostgreSQL performance from that type of test, and it's the sort of
test a lot of people will do on an ad hoc basis.
-Kevin
