In GiST indexes, storing nodes larger than an index page is apparently
not allowed. This prohibits, for example, storing 600 entry float8
arrays in the index. For SP-GiST in PostgreSQL 9.2, it was decided
that this should be documented:
"Individual leaf tuples and inner tuples must fit on a single index
page (8KB by default)."[1]
... but for GiST indexes, this is never mentioned explicitly. The
result was that I wasted many hours developing a GiST index before
noticing it could not be used with my data.
1. http://www.postgresql.org/docs/9.2/static/spgist-implementation.html#SPGIST-LIMITS