Rest API select filter syntax

I can successfully use the select endpoint to retrieve rows from my tables. Now I want to filter the results. I’m pretty sure I need to use the search_columns and search_column_fns parameters, but I cannot figure out the syntax and I can’t find any documentation. Everything I try just results in all rows being returned. That table has 700k rows, so that’s not really an option!

Specifically, I’m querying a table called wp_give_donationmeta. I need to find all rows where meta_key=”_give_payment_form_id” and meta_value=342749.

The SQL query would be:
select donation_id from wp_give_donationmeta where meta_key=”_give_payment_form_id” and meta_value=342749;

What I’ve tried:
search_columns: {“meta_key”: “_give_payment_form_id”, “meta_value”: 342749}
search_column_fns: {“meta_key”:” = “, “meta_value”: ” = “}

Also tried: ” = “, “like”, ” like “, “equal”, “equals”, and finally tried just leaving that parameter out entirely.

More generally, where do I find documentation about how to construct complex filters, which might have several ANDs and ORs?

The page I need help with: [log in to see the link]