[rt-users] PostgreSQL full-text index default type: GiST or GIN

[ktm at rice.edu]

Hi,

I am working on an upgrade from 3.8.x to 4.4.x and I noticed the
following comment in the UPGRADING-4.2 file:

The full-text indexing defaults for PostgreSQL have changed; GiST is now
the suggested index, as well as storing data in a separate
AttachmentsIndex table.  Both changes improve lookup speed.  For
improved search performance, you may wish to drop existing C<tsvector>
and C<GIN> indexes on C<Attachments>, and re-generate the index using
C<rt-setup-fulltext-index>.

I am curious about the benchmarks you used to make this determination?
In particular, the GIN fastscan option can dramatically improve search
performance in versions 9.4 and above. Here is a nice discussion:

http://blog.pgaddict.com/posts/performance-since-postgresql-7-4-to-9-4-fulltext

In addition, GIN indexes are much smaller in PostgreSQL 9.4 and above.
So I am curious about the data that motivated the change to GiST.

Regards,
Ken