Prepared statements prevent the use of connection multiplexing software
such as PGBouncer. Even when PGBouncer is configured for [session mode][1]
there's a possibility that a connection to PostgreSQL can be re-used by
different clients. This leads to errors when clients use session based
features (like prepared statements).
This change removes prepared statements from the PostgreSQL physical
backend. This will allow vault to successfully work in infrastructures
that employ the use of PGBouncer or other connection multiplexing
software.
[1]: https://pgbouncer.github.io/config.html#poolmode
From the PostgreSQL docs
(http://www.postgresql.org/docs/9.4/static/datatype-character.html):
> Tip: There is no performance difference among these three types,
> apart from increased storage space when using the blank-padded type,
> and a few extra CPU cycles to check the length when storing into a
> length-constrained column. While character(n) has performance
> advantages in some other database systems, there is no such advantage
> in PostgreSQL; in fact character(n) is usually the slowest of the
> three because of its additional storage costs. In most situations
> text or character varying should be used instead.
Devin Christensen