Re: [HACKERS] Re: BUG #9210: PostgreSQL string store bug? not enforce check with correct characterSET/encoding

On Fri, Feb 21, 2014 at 05:20:06PM -0500, Tom Lane wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
> > On Wed, Feb 19, 2014 at 08:22:13PM -0500, Tom Lane wrote:
> >> How much of this is back-patch material, do you think?
>
> > None of it. While many of the failures to validate against a character
> > encoding are clear bugs, applications hum along in spite of such bugs and
> > break when we tighten the checks. I don't see a concern to override that
> > here. Folks who want the tighter checking have some workarounds available.
>
> That's certainly a reasonable position to take concerning the changes for
> outside-a-transaction behavior. However, I think there's a case to be
> made for adding the additional pg_verify_mbstr() calls in the back
> branches. We've been promising since around 8.3 that invalidly encoded
> data can't get into a database, and it's disturbing to find that there
> are leaks in that.

I had a dark corner of an app break from the 8.4-vintage change to make
E'abc\000def'::text raise an error rather than truncate the string. The old
behavior was clearly wrong, but I was still glad the change arrived in a major
release; the truncation happened to be harmless for that app. Adding
pg_verify_mbstr() calls creates a similar situation.

Anything broken by the outside-a-transaction behavior change will be in C
code. I'll expect between zero and one reports of breakage from that, so
whether to back-patch that is more academic.

--
Noah Misch
EnterpriseDB http://www.enterprisedb.com