Reconsider design of filters

[simonw]

Follow on from #12. Got some great tips from Bret on Twitter: https://twitter.com/binarybret/status/1291191732579827714

Did you consider making filters part of the schema instead of strings?

A couple of examples of what I’m talking about:

https://grandstack.io/docs/graphql-filtering/

https://pypi.org/project/graphene-sqlalchemy-filter/

https://realtime-location-tracking.demo.hasura.app/console

As a reminder, filters currently look like this:

{
  repos(filters: ["license=apache-2.0", "stargazers_count__gt=10"]) {
  ...

[simonw]

I quite like the design proposed here: graphql-python/graphene-sqlalchemy#164

query {
    pets(filter: {name: {eq: "Lassie"}}) {
    ...

I want to support a list rather than a dictionary, but I do like the idea that each filter looks like this:

{column_name: {operator: "value"}}

[simonw]

So repos(filters: ["license=apache-2.0", "stargazers_count__gt=10"]) would instead be:

{
  repos(filters: [{license: {eq: "apache-2.0"}}, {stargazers_count: {gt: 0}}]) {
  ...

[simonw]

If this means I get autocomplete against column names and operators - plus compatibility with GraphQL variables for the values - this could be a worthwhile change.

[simonw]

I can't figure out how to represent a type in Graphene which looks like this:

filters: is a list of {enum_of_column_names: {enum_of_operators: string-value}}

[simonw]

Full list of operators I would want to support: https://datasette.readthedocs.io/en/stable/json_api.html#column-filter-arguments

[simonw]

I think I know how to do this: filters is a list of usersComparison objects, where usersComparison is a type that has a field for each column name that has a value of type Operation.

The Operation type has a field for each of the allowed operations each matching to a value that's a string. Or maybe even a value that's dependent on the type of the column - so there would be StringOperation and IntegerOperation and FloatOperation types.

[simonw]

Got this working in dev:

{
  repos(filters: [{name: {contains: "datasette"}, stargazers_count: {gt: "10"}}]) {
    nodes {
      full_name
      stargazers_count
    }
  }
}

[simonw]

Got this working too:

{
  repos(filters: [{name: {in: ["datasette", "sqlite-utils"]}, stargazers_count: {gt: "10"}}]) {
    nodes {
      full_name
      stargazers_count
    }
  }
}

[simonw]

Managed to fix the types - so integer columns like stargazers_count can take integer values:

{
  repos(filters: [{name: {in: ["datasette", "sqlite-utils"]}, stargazers_count: {gt: 10}}]) {
    nodes {
      full_name
      stargazers_count
    }
  }
}

[bretwalker]

This is great. I was hacking on this a little last night, but didn't quite get there. Excited to see this progress!

[simonw]

Here's the example in the test:

datasette-graphql/examples/filters.md

Lines 1 to 12 in 87eba0c

	# Table filters
	```graphql
	{
	users(filters:[{score: {gt: 50}}]) {
	nodes {
	name
	score
	}
	}
	}
	```