doc: add examples of creative use of unique expression indexes
authorBruce Momjian <bruce@momjian.us>
Fri, 27 Dec 2019 19:49:08 +0000 (14:49 -0500)
committerBruce Momjian <bruce@momjian.us>
Fri, 27 Dec 2019 19:49:08 +0000 (14:49 -0500)
commita9760d0f3cb523336b5fdd9d6c5985e39a8588a1
tree65a338789f24bb5104da2b4c7ecfdcfc5e2334b1
parent650692a18d29c44c8019545c02ba42c3efd2c964
doc:  add examples of creative use of unique expression indexes

Unique expression indexes can constrain data in creative ways, so show
two examples.

Reported-by: Tuomas Leikola
Discussion: https://postgr.es/m/156760275564.1127.12321702656456074572@wrigleys.postgresql.org

Backpatch-through: 9.4
doc/src/sgml/indices.sgml