[Phoenix-pm] PERL DBI
Loo, Peter # PHX
Peter.Loo at source.wolterskluwer.com
Mon Mar 13 14:01:01 PST 2006
I was wondering if auto commit is turned on by default. Perhaps my
process is committing for each row.
Wolters Kluwer Health
From: phoenix-pm-bounces+peter.loo=source.wolterskluwer.com at pm.org
[mailto:phoenix-pm-bounces+peter.loo=source.wolterskluwer.com at pm.org] On
Behalf Of Bill Nash
Sent: Monday, March 13, 2006 2:47 PM
To: Scott Walters
Cc: phoenix-pm at pm.org
Subject: Re: [Phoenix-pm] PERL DBI
You're very likely pressing up against DB execution overhead.
For starters, you're doing one insert per row. The database side
mechanics of this are:
1. Accept insert.
2. Update indexes.
3. Log query where applicable.
4. Platform specific spooky buffer action and related flushing.
Platform independent, if you're going to chuck a couple million rows
like this, disable your indexing first.
I don't know how you'd optimize this with Oracle, but mysql supports
bulk insert syntax, ala:
insert into foo (a, b, c, d, beer) values (1, 2, 3, 4, 'bar'), (3, 4, 5,
6, 'heineken'), ...;
Even with indexing enabled, this is far more efficient, as indexes are
updated en masse after the insert is accepted.
In psuedocode, something like:
while iterating results,
push result set onto array.
if counter hits 5000,
bulk insert entries stored in array.
I've gotten DBI on good hardware to iterate upwards of 20k rows a
Realistic insert rates are a different animal, because of the i/o (your
mileage may vary depending on media speeds), but 6-8k a second is not
unrealistic. Other factors include the engine type, the data i/o bus of
the machine, etc.
On Mon, 13 Mar 2006, Scott Walters wrote:
> On 0, "David A. Sinck" <phx-pm-list at grueslayer.com> wrote:
>> HAHAHAHAHA. Guess again. There's an instance, at least with MySQL
> Okay, I don't use MySQL heavy (for reasons of it better garbage), so I
> over generalized. I conceede your point that rare bugs will make this
> generalization not always true.
>> \_ and you don't suffer
>> \_ from SQL command length limitations,
>> I bet I could could craft something that hits a buffer still using
>> placeholders if I wanted. :-)
> I didn't say he didn't suffer from *buffer* length considerations --
> that would be foolish indeed. I only said that he doesn't suffer from
> this particular one. I've seen databases cap the command buffer at
> Generally speaking (true in most cases, perhaps false in some) the
> length-counted buffers for placeholder data will be significantly
> larger than the command buffer.
>> \_ and the database doesn't have to parse potentially \_ megs of data
>> just to parse the SQL command,
>> Depends on the driver. MySQL dbd, last I checked, actually sub'd the
>> values in before it got passed to the engine. YMMV.
> That must have been a long time ago indeed. But you caught me -- I
> made another false generalization. I should have said "Generally, "
> in front of it.
> By the way, people who argue small points while ignoring the point of
> what was said annoy me. Did you really think someone on the list
> would be damaged thinking that placeholders always send data out of
> band, even when using Informix?
> I wrote a hasty reply out of desire to be helpful to someone who was
> having trouble with something, not to debate minutia, and have been
> punished for it.
>> Phoenix-pm mailing list
>> Phoenix-pm at pm.org
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