Refs #17448, #28632 -- Fixes related to usage of raw SQL with GIS.

[sir-sigurd]

https://code.djangoproject.com/ticket/17448
https://code.djangoproject.com/ticket/28632

@claudep, I'm not sure if I should restore possibility to select geometry fields without select formatting on Postgres, because it's slower than selecting as bytea by 10%.

[claudep]

I'm fine with that approach. However, if there is a small backwards incompatibility, I would still mention it in the release notes.

[timgraham]

I edited the docs a bit based on my understanding of the issue. Please check that it's accurate.

[sir-sigurd]

@timgraham, I'm not sure if there is sense to mention connection.ops.select here since it wasn’t doc'd anyhow so I don't think someone used it. Perhaps we should say without any condition: "your raw SQL queries need to be updated".

[timgraham]

Good point, I've amended it.

[sir-sigurd]

@timgraham, it was changed on MySQL and SpatiaLite too, but again, I don't think we need this "if" since I'd like to encourage people to use connection.ops.select so things will be more robust to changes in Django.

[timgraham]

Okay, I've amended it again.

[sir-sigurd]

Thanks! Looks good now.