System function RegexMatch is not recognized in v4 preview3

Executing the following query results in the error “‘RegexMatch’ is not a recognized built-in function name.” "SELECT * FROM c WHERE RegexMatch(c.attachment, 's...')"

To Reproduce Execute a query that uses the system function RegexMatch.

Expected behavior The query should execute with no errors and return a set of records.

Actual behavior Provide a description of the actual behavior observed.

Environment summary SDK Version: 4.0.0-preview3

Additional context sample code that reproduces the error:

using Azure.Cosmos;
using Azure.Cosmos.Fluent;
using System;

var connectionString = "AccountEndpoint=https://localhost:8081/;AccountKey=C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw==";

var cosmosClient = new CosmosClientBuilder(connectionString).WithConnectionModeGateway().Build();
var db = await cosmosClient.CreateDatabaseIfNotExistsAsync("Authorization");
var container = await db.Database.DefineContainer("Attachments", "/attachment").CreateIfNotExistsAsync();
var query = new QueryDefinition("SELECT * FROM c WHERE RegexMatch(c.attachment, 's...')");

await foreach(var it in container.Container.GetItemQueryIterator<Attachment>(query))
{
}

public class Attachment
{
    public Guid? id { get; set; }
    public string description { get; set; }
    public string attachment { get; set; }
}

[Mortana89]

The inactivity is indeed painful. Last known date was GTM in May, 2020 that is. Because of the underlying work for the Azure.Core stuff. It looks like it will take a while longer, well, we’re all in IT, we know deadlines 😂 Our biggest reason to chose for V4 was the STJ support indeed, using our custom converters as well. We did this change when we went from 2.2 to 3.1. We’re looking forward to getting some of the new things on V4! (Batch, transactions, new SQL functions 💪💪)!

[ealsur]

Not dead, just not prioritized currently, focus currently is to stabilize V3