In general, datatype I/O functions are supposed to be immutable or at
worst stable. Some contrib I/O functions were, through oversight, not
marked with any volatility property at all, which made them VOLATILE.
Since (most of) these functions actually behave immutably, the erroneous
marking isn't terribly harmful; but it can be user-visible in certain
circumstances, as per a recent bug report from Joe Van Dyk in which a
cast to text was disallowed in an expression index definition.
To fix, just adjust the declarations in the extension SQL scripts. If we
were being very fussy about this, we'd bump the extension version numbers,
but that seems like more trouble (for both developers and users) than the
problem is worth.
A fly in the ointment is that chkpass_in actually is volatile, because
of its use of random() to generate a fresh salt when presented with a
not-yet-encrypted password. This is bad because of the general assumption
that I/O functions aren't volatile: the consequence is that records or
arrays containing chkpass elements may have input behavior a bit different
from a bare chkpass column. But there seems no way to fix this without
breaking existing usage patterns for chkpass, and the consequences of the
inconsistency don't seem bad enough to justify that. So for the moment,
just document it in a comment.
Since we're not bumping version numbers, there seems no harm in
back-patching these fixes; at least future installations will get the
functions marked correctly.
We have seen one too many reports of people trying to use 9.1 extension
files in the old-fashioned way of sourcing them in psql. Not only does
that usually not work (due to failure to substitute for MODULE_PATHNAME
and/or @extschema@), but if it did work they'd get a collection of loose
objects not an extension. To prevent this, insert an \echo ... \quit
line that prints a suitable error message into each extension script file,
and teach commands/extension.c to ignore lines starting with \echo.
That should not only prevent any adverse consequences of loading a script
file the wrong way, but make it crystal clear to users that they need to
do it differently now.
Tom Lane, following an idea of Andrew Dunstan's. Back-patch into 9.1
... there is not going to be much value in this if we wait till 9.2.
It was never terribly consistent to use OR REPLACE (because of the lack of
comparable functionality for data types, operators, etc), and
experimentation shows that it's now positively pernicious in the extension
world. We really want a failure to occur if there are any conflicts, else
it's unclear what the extension-ownership state of the conflicted object
ought to be. Most of the time, CREATE EXTENSION will fail anyway because
of conflicts on other object types, but an extension defining only
functions can succeed, with bad results.
This isn't fully tested as yet, in particular I'm not sure that the
"foo--unpackaged--1.0.sql" scripts are OK. But it's time to get some
buildfarm cycles on it.
sepgsql is not converted to an extension, mainly because it seems to
require a very nonstandard installation process.
Dimitri Fontaine and Tom Lane
