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.
This wasn't addressed in the original patch, but it doesn't take very
much additional code to cover the case, so let's get it done.
Since pg_trgm 1.1 hasn't been released yet, I just changed the definition
of what's in it, rather than inventing a 1.2.
This works by extracting trigrams from the given regular expression,
in generally the same spirit as the previously-existing support for
LIKE searches, though of course the details are far more complicated.
Currently, only GIN indexes are supported. We might be able to make
it work with GiST indexes later.
The implementation includes adding API functions to backend/regex/
to provide a view of the search NFA created from a regular expression.
These functions are meant to be generic enough to be supportable in
a standalone version of the regex library, should that ever happen.
Alexander Korotkov, reviewed by Heikki Linnakangas and Tom Lane
Tom Lane