Database Support for PostgreSQL 10
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The Evergreen database can now be built with PostgreSQL version 10.

This update has implications for developers who write PgTap tests.  In
versions of PostgreSQL prior to 10, one could write `\set ECHO` to
disable the echoing of commands as they were run.  In PostgreSQL
version 10, using `\set` without a value is an error.  One should now
write `\set ECHO none` in order to disable the echoing of commands.
This latter form works in all versions of PostgreSQL currently
supported by Evergreen.

Database Upgrade
++++++++++++++++
If you upgrade your database from a PostgreSQL version of 9.5, or
lower, to PostgreSQL versions 9.6 or 10, you will need to recreate 3
indexes in additon to the normal database upgrade steps.  The index
recreation is necessary because of changes to the PostgreSQL
`unaccent` extension module.

The following snippet of SQL code will do the necessary steps:

[source,sql]
------------------------------------------------------------------------
DROP INDEX actor_usr_first_given_name_unaccent_idx;
DROP INDEX actor_usr_second_given_name_unaccent_idx;
DROP INDEX actor_usr_family_name_unaccent_idx;
CREATE INDEX actor_usr_first_given_name_unaccent_idx ON actor.usr
      (evergreen.unaccent_and_squash(first_given_name));
CREATE INDEX actor_usr_second_given_name_unaccent_idx ON actor.usr
      (evergreen.unaccent_and_squash(second_given_name));
CREATE INDEX actor_usr_family_name_unaccent_idx ON actor.usr
      (evergreen.unaccent_and_squash(family_name));
------------------------------------------------------------------------