Add `Metadata.GetReplicas` APIs With Table Name (Tablet-Compatible)

[sylwiaszunejko]

Background

The current replica resolution APIs exposed by Metadata:

public ICollection<HostShard> GetReplicas(string keyspaceName, byte[] partitionKey)
public ICollection<HostShard> GetReplicas(byte[] partitionKey)

were inherited from the original DataStax driver API. These methods determine replicas without requiring a table name.

This design predates tablet-based replication used in modern ScyllaDB clusters.

Problem

Replica resolution in ScyllaDB can depend on tablet metadata, which is defined per table. Without the table name, the driver cannot correctly resolve replicas when tablets are used.

Because the current C# APIs do not accept a table name, the tablet-based path cannot be used. This effectively forces replica resolution to assume vnode-based replication, which is incorrect for tablet-enabled clusters.

Proposed Solution

Deprecate existing APIs

public ICollection<HostShard> GetReplicas(string keyspaceName, byte[] partitionKey)
public ICollection<HostShard> GetReplicas(byte[] partitionKey)

These APIs cannot correctly support tablet-aware replica resolution.

Introduce new APIs requiring a table name

Example proposal:

public ICollection<HostShard> GetReplicas(string keyspaceName, string tableName, byte[] partitionKey)

This allows the driver to:

• Look up (keyspace, table) in tablet metadata

• Correctly resolve replicas for tablet-based replication

• Fall back to replication strategies when tablets are not present

[Lorak-mmk]

were inherited from the original DataStax driver API.

Does the original Datastax driver have a notion of "shards" in their API? That is surprising.

[sylwiaszunejko]

were inherited from the original DataStax driver API.

Does the original Datastax driver have a notion of "shards" in their API? That is surprising.

The return type was changed to have shards, but the behavior (in terms of tablet/vnodes) was not