Improve documentation of supported lookups on HStore & JSON fields

[Stephen Burrows]

​The documentation of supported lookups on HStore & JSON fields is lacking. For example, HStoreField supports iexact lookups, but the documentation has a scary warning implying that this is not the case:

Since any string could be a key in a hstore value, any lookup other than those listed below will be interpreted as a key lookup.

iexact is not listed below – but neither is contains, which is used directly above the scary warning as an example of how "You can chain other lookups after key lookups". (Actually, contains is listed below, but it's a different contains that applies only to the field level and not to a specific key.)

I suspect that the intended meaning is that all lookups are supported after a key lookup, and that the first lookup on the hstore field must be a key or one of the special lookups listed below.

JSONField does not mention being able to chain lookups after key lookups at all - but I can see people using gt and in ​in blog posts like this. BUT iexact lookups don't currently work on JSONField.

[Mariusz Felisiak]

JSONField-part of this ticket is fixed as a part of ​PR.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 6789ded0:

Fixed #12990, Refs #27694 -- Added JSONField model field.

Thanks to Adam Johnson, Carlton Gibson, Mariusz Felisiak, and Raphael
Michel for mentoring this Google Summer of Code 2019 project and
everyone else who helped with the patch.

Special thanks to Mads Jensen, Nick Pope, and Simon Charette for
extensive reviews.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@…>

[Jacob Walls]

​PR

[Mariusz Felisiak]

Jacob, this patch has nothing to do with the HStore docs.

[cammil]

Yeh. Not sure what that PR has to do with this ticket. Seems completely unrelated to me.

[Jacob Walls]

Thanks, I've asked the author of the unrelated patch to update the ticket number he referenced. Sorry for the noise (and for not reading the patch before linking here).

[Sarah Abderemane]

I'd be happy to help on this issue but HStore is new for me, iexact on HStoreField lookup, it's based on which SQL operator ?
Same as contains @> but it's with case-insensitive or another one ?

[Mariusz Felisiak]

Replying to Sarah Abderemane:

I'd be happy to help on this issue but HStore is new for me, iexact on HStoreField lookup, it's based on which SQL operator ?
Same as contains @> but it's with case-insensitive or another one ?

iexact and other text-lookups should work on ​key transforms on HStoreField because it returns TextField. Maybe it's enough to add a similar note to the one about JSONField, e.g.:

.. note::

    Key transforms can also be chained with: :lookup:`contains`,
    :lookup:`icontains`, :lookup:`endswith`, :lookup:`iendswith`,
    :lookup:`iexact`, :lookup:`regex`, :lookup:`iregex`, :lookup:`startswith`,
    and :lookup:`istartswith`.

This is untested so some tests will also be required.

[Sarah Abderemane]

Thanks Mariusz, I'll try to see for that

[Jacob Walls]

​PR

[Mariusz Felisiak <felisiak.mariusz@…>]

In 533f345:

Refs #27694 -- Added more tests for chaining lookups with HStoreField key transforms.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 1953dd0:

Refs #27694 -- Doc'd lookups that can be chained with HStoreField key transforms.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 7fa946c7:

[4.0.x] Refs #27694 -- Doc'd lookups that can be chained with HStoreField key transforms.

Backport of 1953dd02b6719ee89fddbc3098d86968d79f3cd7 from main

[Mariusz Felisiak <felisiak.mariusz@…>]

In 51e4dbfe:

[3.2.x] Refs #27694 -- Doc'd lookups that can be chained with HStoreField key transforms.

Backport of 1953dd02b6719ee89fddbc3098d86968d79f3cd7 from main