[whatwg] Comments on updated SQL API
beidson at apple.com
Wed Oct 17 11:24:26 PDT 2007
On Oct 17, 2007, at 11:04 AM, Scott Hess wrote:
> On 10/17/07, Brady Eidson <beidson at apple.com> wrote:
>> Assuming using sqlite for the back end, I just wrote a quick little
>> driver that creates a table with 10 columns, then inserts the exact
>> same value into the table 20,000 times.
>> I then ran the exact same test that does the exact same thing, but
>> wraps each individual insert in a transaction.
>> The transaction case is 5% slower.
> But in this case, if you inserted the values 1,000 per transaction, it
> would probably be 10x faster. Maybe 100x faster if you're dealing
> with a network filesystem.
I agree completely. The debate is not whether transactions speed up
batch queries. It's whether they slow down individual queries - which
I have evidence saying they do.
My point is that if we can all end up agreeing it is a performance
hit, then it is an agreed upon mark against the *implicit* transaction.
> The performance case for not using implicit transactions for server
> databases is that it can allow for more concurrency. If the client
> sends a statement to the server without an enclosing transaction, the
> server can minimize the amount of time the transaction has the
> database/table/row locked. If the client has to open the transaction,
> that means a minimum of two additional round trips back to the client
> are introduced (and much worse, if either the client or server are
> very busy).
I'm also concerned about this - the same will be true with SQLite
(minimizing the amount of time a write lock is maintained on the
> For an embedded database like SQLite, things are different. In that
> case, no matter what, you're going to pay a big cost for fsync.
> Making the transaction explicit will have an impact, but I'm really
> surprised that you're seeing 5%. I would bet that you're doing BEGIN
> rather than BEGIN IMMEDIATE, which means that your 5% is probably down
> to upgrading your database locks. If so, that can be worked around by
> implementing the spec using BEGIN IMMEDIATE rather than BEGIN
I will run more detailed numbers on this later, but a quick 1-off on
changing it to BEING IMMEDIATE still indicates a measurable slowdown,
between 1% and 2%
> For the current spec, concurrency isn't a huge issue, because
> everything will be serialized at some level anyhow.
Nothing in the current spec forces 2 different browsing contexts from
operating concurrently, resulting in the possibility of their own
transactions stomping each other.
> [Sorry, don't mean to sound like I'm flip-flopping. My concerns about
> implicit transactions aren't really performance related. :-).]
My concerns about them are more than just performance related ones. A
forced performance penalty just drives me mad ;)
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