Re: That EXPLAIN ANALYZE patch still needs work

Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
>> So the timing is clearly responsible for the additional time I'm
>> personally experiencing and very likely to be that for others also.
>
> Well, that's certainly unsurprising, but the question is why it's such
> a large overhead for you when it's not on other apparently-similar
> kit.
>
> If anyone else is still following this discussion, could you try the
> test case Simon gave a bit earlier (select count(*) from 100000-row
> table, check \timing with and without explain analyze)? If we could
> get a clearer picture of which platforms show the problem and which
> don't, maybe we could make some progress.
>
> (BTW, I just tried it on my Apple Powerbook G4, and got results in
> line with what I get elsewhere. So I've now tried it on three very
> different CPU types and OSes, and not duplicated Simon's problem on
> any of them.)
>

$ psql
Welcome to psql 8.1.4, the PostgreSQL interactive terminal.

Type: \copyright for distribution terms
\h for help with SQL commands
\? for help with psql commands
\g or terminate with semicolon to execute query
\q to quit

ler=# create table test1(id int);
CREATE TABLE
ler=# insert into test1 select * from generate_series(1,100000);
INSERT 0 100000
ler=# \timing
Timing is on.
ler=# select count(*) from test1;
count
--------
100000
(1 row)

Time: 39.191 ms
ler=# explain analyze select count(*) from test1;
QUERY PLAN

----------------------------------------------------------------------------
----------------------------------------
Aggregate (cost=1988.18..1988.19 rows=1 width=0) (actual
time=282.899..282.901 rows=1 loops=1)
-> Seq Scan on test1 (cost=0.00..1698.74 rows=115774 width=0) (actual
time=0.007..147.845 rows=100000 loops=1)
Total runtime: 282.987 ms
(3 rows)

Time: 283.764 ms
ler=# \q
$ uname -a
FreeBSD thebighonker.lerctr.org 6.1-STABLE FreeBSD 6.1-STABLE #59: Thu Jun
1 09:40:47 CDT 2006
root(at)thebighonker(dot)lerctr(dot)org:/usr/obj/usr/src/sys/THEBIGHONKER amd64
$ sysctl hw
hw.machine: amd64
hw.model: Intel(R) Xeon(TM) CPU 3.00GHz
hw.ncpu: 4
hw.byteorder: 1234
hw.physmem: 4286132224
hw.usermem: 4003151872
hw.pagesize: 4096
hw.floatingpoint: 1
hw.machine_arch: amd64
hw.realmem: 5368709120

[snip]

the database is 8.1.4
--
Larry Rosenman http://www.lerctr.org/~ler
Phone: +1 512-248-2683 E-Mail: ler(at)lerctr(dot)org
US Mail: 430 Valona Loop, Round Rock, TX 78681-3893