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Brad Fitzpatrick 277047f52a database/sql: fix driver Conn refcounting with prepared statements
The refcounting of driver Conns was completedly busted and
would leak (be held open forever) with any reasonable
load. This was a significant regression from Go 1.0.

The core of this patch is removing one line:

     s.db.addDep(dc, s)

A database conn (dc) is a resource that be re-created any time
(but cached for speed) should not be held open forever with a
dependency refcount just because the Stmt (s) is alive (which
typically last for long periods of time, like forever).

The meat of the patch is new tests. In fixing the real issue,
a lot of tests then failed due to the fakedb_test.go's paranoia
about closing a fakeConn while it has open fakeStmts on it. I
could've ignored that, but that's been a problem in the past for
other bugs.

Instead, I now track per-Conn open statements and close them
when the the conn closes.  The proper way to do this would've
been making *driverStmt a finalCloser and using the dep mechanism,
but it was much more invasive. Added a TODO instead.

I'd like to give a way for drivers to opt-out of caring about
driver.Stmt closes before a driver.Conn close, but that's a TODO
for the future, and that TODO is added in this CL.

I know this is very late for Go 1.1, but database/sql is
currently nearly useless without this.

I'd like to believe all these database/sql bugs in the past
release cycle are the result of increased usage, number of
drivers, and good feedback from increasingly-capable Go
developers, and not the result of me sucking.  It's also hard
with all the real drivers being out-of-tree, so I'm having to
add more and more hooks to fakedb_test.go to simulate things
which real drivers end up doing.

Fixes #5323

R=golang-dev, snaury, gwenn.kahz, google, r
CC=golang-dev
https://golang.org/cl/8836045
2013-04-25 14:45:56 -07:00
api api: update next.txt; add io.ErrNoProgress 2013-04-20 17:20:58 -07:00
doc all: fix typos 2013-04-24 04:46:14 +08:00
include include/plan9/libc.h: fix Plan 9 build 2013-03-30 19:05:00 +08:00
lib lib/time: update to IANA 2013c 2013-04-22 16:28:42 -07:00
misc misc/cgo/testso: enable test on windows 2013-04-23 04:42:04 +08:00
src database/sql: fix driver Conn refcounting with prepared statements 2013-04-25 14:45:56 -07:00
test cmd/gc: initialize t->width in dgcsym() if required 2013-04-25 18:47:12 +02:00
.hgignore build: update Makefile to track source code dependencies better 2012-03-13 03:31:11 +08:00
.hgtags untag go1.1beta1 2013-04-04 13:51:20 +11:00
AUTHORS A+C: Nicholas Presta (individual CLA) 2013-04-09 13:12:31 +10:00
CONTRIBUTORS A+C: Nicholas Presta (individual CLA) 2013-04-09 13:12:31 +10:00
favicon.ico godoc: update favicon 2012-10-11 17:02:36 +11:00
LICENSE doc: update licensing text one more time 2012-03-27 15:09:13 +11:00
PATENTS LICENSE: separate, change PATENTS text 2010-12-06 16:31:59 -05:00
README build: update, streamline documentation for new $GOBIN 2010-08-24 20:00:50 -04:00
robots.txt godoc: serve robots.txt raw 2011-02-19 05:46:20 +11:00

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