[Activity log] Make database writes in counting policy more robust

[Activity log] Make database writes in counting policy more robust

Rework the way that new actions are logged in the counting policy so
that it properly handles the case where there are duplicate records that
weren't properly coalesced.  (Duplicate records could arise from
clearing URL history, for example.)

This comes at the cost of additional queries--an update always takes 2
queries, instead 1 or 2 as before.  However, benchmarking shows the cost
to be not much different (worst case was ~5% slower, other cases were
indistinguishable or even a bit faster).

BUG=279465
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=221860

[mvrable, 2013-09-06 18:34:49]

Adrienne, would you have a chance to review this change?  This makes sure that
counts are updated accurately when duplicate rows are present, which can come up
now that https://codereview.chromium.org/23785002/ has been committed.

--Michael Vrable

[felt, 2013-09-06 20:53:57]

lgtm, with one request: Can you add some explanation of this as a method comment
in counting_policy.h?

https://codereview.chromium.org/23907004/diff/3001/chrome/browser/extensions/...
File chrome/browser/extensions/activity_log/counting_policy.cc (right):

https://codereview.chromium.org/23907004/diff/3001/chrome/browser/extensions/...
chrome/browser/extensions/activity_log/counting_policy.cc:228: " WHERE time >= ?
AND time < ?";
by the way, I recently discovered the existence of the BETWEEN clause. I didn't
know about it originally. I don't think it makes any difference, just mentioning
it.

[mvrable, 2013-09-06 21:48:33]

This version should improve the comments.

https://codereview.chromium.org/23907004/diff/3001/chrome/browser/extensions/...
File chrome/browser/extensions/activity_log/counting_policy.cc (right):

https://codereview.chromium.org/23907004/diff/3001/chrome/browser/extensions/...
chrome/browser/extensions/activity_log/counting_policy.cc:228: " WHERE time >= ?
AND time < ?";
On 2013/09/06 20:53:57, felt wrote:
> by the way, I recently discovered the existence of the BETWEEN clause. I
didn't
> know about it originally. I don't think it makes any difference, just
mentioning
> it.

I hadn't thought of using BETWEEN (I usually don't).  I think I'll leave this as
is, however, because between allows equality at both endpoints and here I don't.
 I could write it as "time BETWEEN ? and ?-1", but I think it's clearer as is.

[commit-bot: I haz the power, 2013-09-06 21:50:52]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mvrable@chromium.org/23907004/13001

[commit-bot: I haz the power, 2013-09-07 02:18:54]

Change committed as 221860