IssueTracker

Using JSON_EXTRACT and JSON_EXTRACT_SCALAR I see no way to turn a `string` representing a json array into an `array<string>` representing each json value in the json array. Right now, we use a js udf to achieve this, which makes our queries slow (we're starting to see query timeouts on our bigger tables) and limits our query concurrency by a factor of 10x (6 concurrent udf queries instead of the usual 50):

65 / ~350

```
create temp function json_extract_array(s string, key string) returns array<string> language js as """
    try {
        var xs = JSON.parse(s)[key];
        return xs == null ? null : xs.filter((x,i) => x != null).map((x,i) => x.toString());
    } catch (e) {
        throw e + ', on input string s: ' + s;
    }
"""
```

In particular, we're starting to see persistent query timeouts on a table with:
- ~5M rows
- ~350 columns
- ~65 are strings representing json arrays, which we're parsing all of using our `json_extract_array` udf

Questions:
1. Is there a better way to achieve this than using a udf?
2. Is this already on the team's internal roadmap?