Add details for installing postgres extensions

[Alex Krupp]

Currently for installing the Postgres HStoreExtension, the documentation is as follows:

Setup the hstore extension in PostgreSQL before the first CreateModel or AddField operation by adding a migration with the HStoreExtension operation.

However there is no explanation of how to do this. It also seems like the migrations would need to be run as superuser, so doing this in a secure way should be incorporated into the instructions.

[Tim Graham]

The migration operations would look like this:

operations = [
    HStoreExtension(),
]

I thought one could infer that from the instructions, but I guess not. Does that code example make sense?

If the database user doesn't have superuser privileges, then I think the simplest solution is to recommend creating the extension manually, outside of Django migrations.

[Troy Grosfield]

I too thought this step was quite confusing. @timgraham, your code example should be included in Django's doc for clarity. However, why isn't the HStoreExtension migration operation added when you first run python manage.py makemigrations?

[Tim Graham]

How does this ​pull request look?

[Tim Graham <timograham@…>]

In 9ef2615:

Fixed #24811 -- Added details on installing PostgreSQL extensions.

[Tim Graham <timograham@…>]

In 9def46c:

[1.8.x] Fixed #24811 -- Added details on installing PostgreSQL extensions.

Backport of 9ef2615d4968ed52dbd88a19f03746a2f16c7511 from master

[Madeleine Price Ball]

I get a syntax error (using Postgres 9.3.7) due to the single quotes when running CREATE EXTENSION IF NOT EXISTS 'hstore';

mydb=# CREATE EXTENSION IF NOT EXISTS 'hstore';
ERROR:  syntax error at or near "'hstore'"
LINE 1: CREATE EXTENSION IF NOT EXISTS 'hstore';
                                       ^

It works fine with double quotes:

mydb=# CREATE EXTENSION IF NOT EXISTS "hstore";
CREATE EXTENSION

I think the documentation needs to be changed to use double quotes. Thanks!

[Tim Graham]

Thanks for the report. I think we can use the syntax from the PostgreSQL docs which omits any quotes.

[Tim Graham <timograham@…>]

In c954931:

Refs #24811 -- Fixed syntax error in CREATE EXTENSION example query.

[Tim Graham <timograham@…>]

In b8dce1af:

[1.8.x] Refs #24811 -- Fixed syntax error in CREATE EXTENSION example query.

Backport of c954931abd17f8efaa6b7662ac2916dbf47d2978 from master