pgsql: Add _bt_binsrch() scantid assertion to nbtree.

Add _bt_binsrch() scantid assertion to nbtree.

Assert that _bt_binsrch() binary searches with scantid set in insertion
scankey cannot be performed on leaf pages. Leaf-level binary searches
where scantid is set must use _bt_binsrch_insert() instead.

_bt_binsrch_insert() is likely to have additional responsibilities in
the future, such as searching within GIN-style posting lists using
scantid. It seems like a good idea to tighten things up now.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/55d015bde05311cbaaf16424e3aa05c37946cd8a

Modified Files
--------------
src/backend/access/nbtree/nbtsearch.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)