code review 159910045: dashboard: faster perf data fetching

dashboard: faster perf data fetching
Use single query to fetch commit runs and metric runs (instead of individual selects).
Hopefully this enables some kind of prefetching.
But more importantly it allows to work around "gaps" in commit nums,
as we only fetch data that is actually in the database
and don't try to query all commit runs in the "gap".

[dvyukov, 2014-10-16 17:53:50]

Hello adg@golang.org (cc: golang-codereviews@googlegroups.com, rsc@golang.org),

I'd like you to review this change to
https://code.google.com/p/go.tools

[adg, 2014-10-17 07:27:53]

LGTM

[dvyukov, 2014-10-17 07:38:16]

*** Submitted as
https://code.google.com/p/go/source/detail?r=ce0e0a1d6a53&repo=tools ***

dashboard: faster perf data fetching
Use single query to fetch commit runs and metric runs (instead of individual
selects).
Hopefully this enables some kind of prefetching.
But more importantly it allows to work around "gaps" in commit nums,
as we only fetch data that is actually in the database
and don't try to query all commit runs in the "gap".

LGTM=adg
R=adg
CC=golang-codereviews, rsc
https://codereview.appspot.com/159910045