Implements the EXISTS filter #2484
Description
After the following discussion and a meeting with @gmourier and @loiclec; https://github.com/meilisearch/product/issues/22
The first version of the filter should be implemented with the following syntax;
The keyword is postfixed
vvvvv
price EXISTS
^ ^
A NOT can be prefixed or infixed
vvv vvv
NOT price NOT EXISTS
With the following set of documents;
{ "id": 1, "product": "T-shirt", "price": 20, "color": "yellow" }
{ "id": 2, "product": "T-shirt", "color": "red" }
- The filter
price EXISTSwill select the first document. - The filter
price NOT EXISTSorNOT price EXISTSwill select only the second document.
If a field contains an empty array or a null value, it's considered as existing:
{ "id": 1, "product": "T-shirt", "price": 20, "color": "yellow" }
{ "id": 2, "product": "T-shirt", "price": [], "color": "red" }
{ "id": 3, "product": "T-shirt", "price": null, "color": "red" }
{ "id": 4, "product": "T-shirt", "color": "red" }
Here price EXISTS matches documents 1, 2 and 3.
This will ease the handling of incomplete documents. For example, if you want to return all T-shirt that cost less than 20€ or that doesn't have a price specified, you will be able to write product = "T-shirt" AND (price < 20 OR price NOT EXISTS).
That was not possible previously.