Re: BUG #5126: convert_to preventing index scan

>>>>> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:

 Tom> The conversion itself is dependent on changeable catalog
 Tom> entries, ie, pg_conversion.  So "stable" seems the appropriate
 Tom> marking to me.

 >> That sounds like a bit of a stretch to me... we treat lots of
 >> stuff as immutable which is actually easier to change than
 >> pg_conversion entries (OS locale definitions for example).

 Tom> Um ... locale *is* fixed within a given database, or at least
 Tom> LC_COLLATE and LC_CTYPE are.  If you see cases where we have
 Tom> this wrong, they may need to be revisited.

The value of LC_CTYPE etc. is fixed, but the meaning that the OS
assigns to that value can be changed (arguably more easily than
changing pg_conversion, now that we don't allow builtin conversion
funcs to be used for conversions other than the one they are coded
for).

Of course, changing the definition of a locale will break everything
until you reindex, etc., but we put up with that because the
alternatives are clearly silly.

--
Andrew.