Re: text search changes vs. binary upgrade

Noah Misch <noah@leadboat.com> writes:
> Commit bb14050 said:
>     - change order for tsquery, so, users, who has a btree index over tsquery,
>       should reindex it

We undid that in 1ec4c7c05, no?  (Even if we didn't, the usefulness
of a btree index on tsquery seems negligibly small.)

> Commit 61d66c4 may or may not warrant pg_upgrade treatment:
>     Fix support of digits in email/hostnames.

The general theory about changes in text search parser and dictionary
behavior has always been that a reindex is not required, because that does
not invalidate the derived data in the same sort of way that changing,
say, btree sort order of a datatype would.  At worst, searches for the
specifically affected words might fail to find relevant entries because
to_tsvector now produces a different list of lexemes than before (and
those new lexemes are not in the index, the old ones are).  If the
affected set of words is sufficiently large and relevant to her use-case,
a user might judge that rebuilding derived tsvector data is worth her
trouble.  But I am dubious that pg_upgrade should issue guidance
unconditionally telling people to do it.  Most people probably aren't
going to have any noticeable amount of data that's affected by this change.

If we did worry about this for 61d66c4, then for example the unaccent
changes would also be problematic, and probably the ispell changes too.
I'm inclined to just group all those things in the release notes and
provide text counseling users to think about how much those changes affect
their full-text data and whether rebuilding derived tsvectors would be
worth it.
        regards, tom lane