Watermelondb: Support like and notLike operator

[ieschalier]

What do you think about add like and notLike operator to query ?

It could be a good optimization for applications with search feature in large amount of data.

Proposal

commentCollection.query(
  Q.where('label', Q.like('a%')),
)

[radex]

this should be possible, not super difficult, but not trivial either. If someone wants to implement this, I can give guidance as for where to start

[ieschalier]

I'm ok to implement it. Can you give me some advice ?

[radex]

Sure, you need these parts:

• QueryDescription/index.js is where operators are defined
• adapters/sqlite/encodeQuery is where the query is converted to SQL (react native)
• adapters/lokijs/encodeQuery is the same but for LokiJS (web)
• observation/encodeMatcher is where the query is encoded into a matcher function, which can tell whether a Model object matches a query or not. This is necessary for observing queries. More details here: https://github.com/Nozbe/WatermelonDB/issues/15#issuecomment-419713849
• Tests! The first three items have low-level unit tests to see if the right output is generated from the query language
• … and then there's the integration test in __tests__/databaseTests that checks every single operator on every supported database to see if it actually works

[ieschalier]

@radex My first PR to WatermelonDB has been sent 🙂. I'm waiting for your feedback

[sonikro]

Hello, great work guys.

While this is not approved yet, is there any alternative way of doing a LIKE query ? I really need this feature to implement a filter by Customer Name in my App.

Thanks.

[radex]

@sonikro if it needs to be a fuzzy search… no good solution comes to mind, sorry. I suggest you temporarily use the Watermelon fork @ieschalier has. His PR is almost ready, should work fine — but might take a week or two until it's realeased

[sonikro]

Thanks @radex , that's exactly what Im doing right now.
EDIT: Also, thanks @ieschalier for developing it :+1:

[radex]

merged and shipped. cc @sonikro