Add support for filter operators

[AbegaM]

Purpose of the Issue

I would like to add support for filtering operators in Soul. Currently, Soul filters table fields with the _filters field, which works fine, but I am unable to filter items using the operators <, >, <=, >=, and !=. For example, I can fetch an invoice from Soul using the following URL, which works fine:

   localhost:8000/api/tables/invoices/rows?_filters=Total:1.98

However, I might want to fetch invoices where the total value is less than 2 or greater than 2, and I cannot achieve this with Soul's current functionality.

Proposed Solution

There could be several options to add this feature, but I propose passing double underscores after the column name. Here are some examples:

Greater than (>):

localhost:8000/api/tables/invoices/rows?_filters=Total__gt:3

Less than (<):

localhost:8000/api/tables/invoices/rows?_filters=Total__lt:3

Greater than or equal to (>=):

localhost:8000/api/tables/invoices/rows?_filters=Total__gte:3

Less than or equal to (<=):

localhost:8000/api/tables/invoices/rows?_filters=Total__lte:3

Not equal to (!=):

localhost:8000/api/tables/invoices/rows?_filters=Total__neq:3

This proposal would allow users to filter table rows using the operators listed above, making Soul's functionality more flexible and powerful.

[AbegaM]

Hello @thevahidal

Could you please review my feature request issue and let me know what you think? I'm planning to start working on a pull request soon. Thank you!"

[IanMayo]

Note: this strategy for providing filter operators appears to match the one used in react-admin:
https://marmelab.com/react-admin/FilteringTutorial.html#filter-operators

[thevahidal]

Thanks for the feature request @AbegaM. This is for sure a must have feature for Soul and I think the way your proposal works is really great!
Please start your PR and let me know if there's anything I can help with it.

[AbegaM]

Thank you @thevahidal, i will start working on the PR 👍

[IanMayo]

BTW - @thevahidal - you can use the repo settings to delete branches once the PR is merged. It's a house-keeping chore that helps out just a little.

[thevahidal]

Hey @IanMayo, I'll do it for sure.

[IanMayo]

Hello @thevahidal - any chance of a new release? I have a PR in another project that is blocked, waiting on this feature.

[IanMayo]

It appears that the existing filters to not match for null. When we provide _filters=batch:null, I suspect Soul is doing a string comparison.

So, I believe we need a filter attribute for the SQLite value of null. Maybe a new __null operator?

[thevahidal]

Hey @IanMayo sorry I wasn't available for the past couple of days, I'm ok to do the release, but do you think we should fix the null thing and then proceed with the release?

[IanMayo]

Good plan, let's defer release until we can filter for null.

[thevahidal]

It seems that @AbegaM started a new PR for the matter https://github.com/thevahidal/soul/pull/117/files, let's release these two together.

[IanMayo]

Closed in #117