On 11/22/11 10:53 AM, Andres Freund wrote:
20M rows inserted inside one transaction doesn't cause*that* many writes.
indeed, I just ran a test on a fairly beefy server, a 2U HP DL180G6 with
dual Sandy Bridge E5660 CPUs (12 cores, 24 threads), 48GB, and 20 x 15k
SAS RAID10 on a 1GB SAS2 raid card for the database... its capable of
fairly high IOPS.
=> create table x (id serial primary key, key integer, val text);
NOTICE: CREATE TABLE will create implicit sequence "x_id_seq" for
serial column "x.id"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "x_pkey"
for table "x"
CREATE TABLE
=> \timing
Timing is on.
=> insert into x (key,val) values (generate_series(1,20000000),
to_char(trunc(random()*1000000),'999999'));
INSERT 0 20000000
Time: 160205.678 ms
=> select * from x limit 10;
id | key | val
----+-----+---------
1 | 1 | 211882
2 | 2 | 161866
3 | 3 | 785931
4 | 4 | 673363
5 | 5 | 342551
6 | 6 | 753181
7 | 7 | 474393
8 | 8 | 309599
9 | 9 | 958952
10 | 10 | 382413
(10 rows)
Time: 0.123 ms
=> select count(*) from x;
count
----------
20000000
(1 row)
Time: 2014.837 ms
=> select count(*) from x;
count
----------
20000000
(1 row)
Time: 1590.407 ms
=> create index on x (key);
CREATE INDEX
Time: 25392.231 ms
and just for the heck of it some more inserts with and without the 2nd
index...
=> insert into x (key,val) values (generate_series(1,20000000),
to_char(trunc(random()*1000000),'999999'));
INSERT 0 20000000
Time: 227619.123 ms
=> drop index x_key_idx;
DROP INDEX
Time: 1217.443 ms
=> insert into x (key,val) values (generate_series(1,20000000),
to_char(trunc(random()*1000000),'999999'));
INSERT 0 20000000
Time: 165521.898 ms
=> insert into x (key,val) values (generate_series(1,20000000),
to_char(trunc(random()*1000000),'999999'));
INSERT 0 20000000
Time: 164767.536 ms
=> select count(*) from x;
count
----------
80000000
(1 row)
Time: 9048.421 ms
=> create index on x (key);
CREATE INDEX
Time: 116479.548 ms
=> insert into x (key,val) values (generate_series(1,20000000),
to_char(trunc(random()*1000000),'999999'));
INSERT 0 20000000
Time: 254630.371 ms
so, with one index (primary key), 20M inserts of a couple small fields
is taking 160 seconds. with two indexes, 225-250 seconds... creating
that 2nd index is taking 115 seconds now. after this last step, the
table is 9800MB, of which about 2GB is the PK and 3.4GB is the 2nd index.
--
john r pierce N 37, W 122
santa cruz ca mid-left coast
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