core dump? OID/database corruption?

An obscure series of events seems to cause a core dump and OID
corruption:

-- tolower function for varchar
create function varchar_lower(varchar) returns varchar
as '/usr/local/lib/pgcontains.so', 'pglower'
language 'c';

create index ztables_title_ndx on ztitles ( varchar_lower (title) ) ;

vacuum analyze ;

{ leave }

at some point come back

drop function varchar_lower (varchar) ;

create function varchar_lower(varchar) returns varchar
as '/usr/local/lib/pgcontains.so', 'pglower'
language 'c';

and strange things start to happen.

I realize that (and only belatedly) once I drop the function the index
is corrupt, but it seems there are invalid oids when I try to dump the
database, and dumping some tables caused a core dump.

I didn't save the data, I was in live service panic mode.

I have a shared library of functions I use in Postgres and I do a drop /
create for an install script. I realize this is a little indiscriminate,
and at least unwise, but I think postgres should be able to handle this.

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