How does one drop a template database from PostgreSQL?

Question

postgres=# DROP DATABASE template_postgis;
ERROR:  cannot drop a template database

http://www.postgresql.org/docs/9.1/static/manage-ag-templatedbs.html

Answer 1

You can use the alter database command. Much simpler and safer than upsetting metadata.

postgres=# create database tempDB is_template true;
CREATE DATABASE
postgres=# drop database tempDB;
ERROR:  cannot drop a template database
postgres=# alter database tempDB is_template false;
ALTER DATABASE
postgres=# drop database tempDB;
DROP DATABASE
postgres=# 

Documentation

Answer 2

postgres=# UPDATE pg_database SET datistemplate='false' WHERE datname='template_postgis';
UPDATE 1
postgres=# DROP DATABASE template_postgis;
DROP DATABASE
postgres=# 

Answer 3

update pg_database set datistemplate=false where datname='template0';
update pg_database set datistemplate=false where datname='template1';

....

Creating script to analyze new cluster                      ok
Creating script to delete old cluster                       ok
Checking for hash indexes                                   ok

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