Stephen Frost wrote on 22.04.2009 23:51:
>>> What about 40000 individual prepared inserts? Just curious about it.
>> 40000 inserts, one prepared statement each (constructing the prepared
>> statement only once), in a single transaction: 1.68s
>>
>> I'm surprised that there's any win here at all.
>
> For a single column table, I wouldn't expect much either. With more
> columns I think it would be a larger improvement.
Out of curiosity I did some tests through JDBC.
Using a single-column (integer) table, re-using a prepared statement took about
7 seconds to insert 100000 rows with JDBC's batch interface and a batch size of 1000
Using a prepared statement that had a 1000 (?) after the insert (insert into foo
values (?), (?), ...) the insert took about 0.8 seconds. Quite an improvement
I'd say.
Then I switched to a three column table (int, varchar(500), varchar(500)).
Insert using a preparedstatement with batch (first scenario) now was ~8.5
seconds, whereas the multi-value insert now took ~3 seconds. So the difference
got smaller, but still was quite substantial. This was inserting relatively
small strings (~20 characters) into the table
When increasing the size of the inserted strings, things began to change. When I
bumped the length of the strings to 70 and 200 characters, the multi-value
insert slowed down considerably. Both solutions now took around 9 seconds.
The multi-value solution ranged between 7 and 9 seconds, whereas the "regular"
insert syntax was pretty constant at roughly 9 seconds (I ran it about 15 times).
So it seems, that as the size of the row increases the multi-value insert loses
its head-start compared to the "regular" insert.
I also played around with batch size. Going beyond 200 didn't make a big
difference.
For the JDBC batch, the batch size was the number of rows after which I called
executeBatch() for the multi-value insert, this was the number of tuples I sent
in a single INSERT statement.
The multi-value statement seems to perform better with lower "batch" sizes
(~10-50) whereas the JDBC batching seems to be fastest with about 200 statements
per batch.
Thomas
